Books:

Shadowlands: Quest for Mirror Matter in the Universe

download

Cosmoparticle Physics

order

Cosmology of the Mirror Universe

Paolo Ciarcelluti

We describe the implications on the structure formation, the cosmic microwave background (CMB) and the large scale structure (LSS) for a Universe in which a significant part of dark matter is made of mirror baryons. Being the microphysics of the mirror baryons identical to the one of the usual baryons, we need only two extra thermodynamical parameters to describe our model: the temperature of the mirror plasma (limited by the BBN) and the amount of mirror baryonic matter. We extend the Jeans theory in order to study the structure formation mechanism in linear regime. Using a numerical code, we compute the temporal evolution of perturbations, the CMB anisotropies and the LSS power spectra. We show as the decoupling time and the dissipative Silk scale of the mirror baryons (both being different than for the ordinary ones) are key features for the evolution of a Mirror Universe, and induces specific signatures on the power spectra. We analyse the dependence of both CMB and LSS spectra on the mirror sector temperature and on the amount of mirror baryons. Confronting with the present observational data, we show that for x < 0.3 the dark matter could be constituted entirely by mirror baryons, since in this case mirror baryons at linear scales behave essentially like cold dark matter (CDM) and substantial deviations are expected only at smaller scales which have undergone non-linear growth from relatively large redshifts. In the case of x > 0.3 the pattern of the LSS power spectrum excludes the possibility of dark matter consisting entirely of mirror baryons, but they could present as admixture to the conventional CDM.

Ph.D. thesis

Articles:

Early universe, nucleosynthesis, structure formation etc.

Dark matter direct detection experiments

Effects of mirror matter on (planetary) physics

Orthopositronium

Neutrinos

Ultra High Energy Cosmic Rays

Supernova explosions, Gamma ray bursts etc.

Extra solar planets, isolated planets, mirror stars etc.

Reviews

Theory

Early universe, structure formation, nucleosynthesis etc.:

Photon Mixing in Domain Walls and the Cosmic Coincidence Problem

Jarah Evslin, Malcolm Fairbairn

A model is presented where there exists another U(1) gauge group which is extremely weakly coupled to that of QED except inside the core of domain walls. It is possible to choose parameters such that standard model photons crossing such a wall are mixed maximally with the 'para-photons' of the other U(1). We use this model to explain the apparent low luminosity of high redshift supernovae. A possible mechanism is outlined where the domain walls correspond to changes in the relative orientation of branes in a compact space. The model is rather contrived but has the advantage that for a wide range of values it can solve the cosmic coincidence problem - an observer at any redshift would come to the conclusion that their universe had recently started to accelerate.

Cosmology with mirror dark matter I: linear evolution of perturbations

P. Ciarcelluti

This is the first paper of a series devoted to the study of the cosmological implications of the parallel mirror world with the same microphysics as the ordinary one, but having smaller temperature, with a limit set by the BBN constraints. The difference in temperature of the ordinary and mirror sectors generates shifts in the key epochs for structure formation, which proceeds in the mirror sector under different conditions. We consider adiabatic scalar primordial perturbations as an input and analyze the trends of all the relevant scales for structure formation (Jeans length and mass, Silk scale, horizon scale) for both ordinary and mirror sectors, comparing them with the CDM case. These scales are functions of the fundamental parameters of the theory (the temperature of the mirror plasma and the amount of mirror baryonic matter), and in particular they are influenced by the difference between the cosmological key epochs in the two sectors. Then we used a numerical code to compute the evolution in linear regime of density perturbations for all the components of a Mirror Universe: ordinary baryons and photons, mirror baryons and photons, and possibly cold dark matter. We analyzed the evolution of the perturbations for different values of mirror temperature and baryonic density, and obtained that for x=T'/T less than a typical value x_eq, for which the mirror baryon-photon decoupling happens before the matter-radiation equality, mirror baryons are equivalent to the CDM for the linear structure formation process. Indeed, the smaller the value of x, the closer mirror dark matter resembles standard cold dark matter during the linear regime.

Int.J.Mod.Phys. D14 (2005) 187-222

Cosmology with mirror dark matter II: Cosmic Microwave Background and Large Scale Structure

P. Ciarcelluti

This is the second paper of a series devoted to the study of the cosmological implications of the existence of mirror dark matter. The parallel hidden mirror world has the same microphysics as the observable one and couples the latter only gravitationally. The primordial nucleosynthesis bounds demand that the mirror sector should have a smaller temperature T' than the ordinary one T, and by this reason its evolution can be substantially deviated from the standard cosmology. In this paper we took scalar adiabatic perturbations as the input in a flat Universe, and computed the power spectra for ordinary and mirror CMB and LSS, changing the cosmological parameters, and always comparing with the CDM case. We found differences in both the CMB and LSS power spectra, and we demonstrated that the LSS spectrum is particularly sensitive to the mirror parameters, due to the presence of both the oscillatory features of mirror baryons and the collisional mirror Silk damping. For x<0.3 the mirror baryon-photon decoupling happens before the matter-radiation equality, so that CMB and LSS power spectra in linear regime are equivalent for mirror and CDM cases. For higher x-values the LSS spectra strongly depend on the amount of mirror baryons. Finally, qualitatively comparing with the present observational limits on the CMB and LSS spectra, we show that for x<0.3 the entire dark matter could be made of mirror baryons, while in the case x>0.3 the pattern of the LSS power spectrum excludes the possibility of dark matter consisting entirely of mirror baryons, but they could present as admixture (up to 50%) to the conventional CDM.

Int.J.Mod.Phys. D14 (2005) 223-256

Structure formation, CMB and LSS in a mirror dark matter scenario

P. Ciarcelluti

In the mirror world hypothesis the mirror baryonic component emerges as a possible dark matter candidate. Here we study the behaviour of the mirror dark matter and the differences from the more familiar CDM candidate for structure formation, cosmic microwave background and large scale structure. We show mirror models for CMB and LSS power spectra and compare them with observations, obtaining bounds on the mirror parameter space.

Frascati Phys.Ser. 555 (2004) 1

Spheroidal galactic halos and mirror dark matter

R. Foot, R. R. Volkas

Mirror matter has been proposed as a dark matter candidate. It has several very attractive features, including automatic stability and darkness, the ability to mimic the broad features of cold dark matter while in the linear density perturbation regime, and consistency with all direct dark matter search experiments, both negative (e.g. CDMS II) and positive (DAMA). In this paper we consider an important unsolved problem: Are there plausible reasons to explain why most of the mirror matter in spiral galaxies exists in the form of gaseous {\it spheroidal} galactic halos around ordinary matter {\it disks}? We compute an order-of-magnitude estimate that the mirror photon luminosity of a typical spiral galaxy today is around $10^{44}$ erg/s. Interestingly, this rate of energy loss is similar to the power supplied by ordinary supernova explosions. We discuss circumstances under which supernova power can be used to heat the gaseous part of the mirror matter halo and hence prevent its collapse to a disk. The {\it macro}scopic ordinary-mirror asymmetry plays a fundamental role in our analysis.

Phys.Rev. D70 (2004) 123508

Explaining $\Omega_{Baryon} \approx 0.2 \Omega_{Dark}$ through the synthesis of ordinary matter from mirror matter: a more general analysis

R. Foot, R. R. Volkas

The emerging cosmological picture is of a spatially flat universe composed predominantly of three components: ordinary baryons ($\Omega_B \approx 0.05$), non-baryonic dark matter ($\Omega_{Dark} \approx 0.22$) and dark energy ($\Omega_{\Lambda} \approx 0.7$). We recently proposed that ordinary matter was synthesised from mirror matter, motivated by the argument that the observed similarity of $\Omega_B$ and $\Omega_{Dark}$ suggests an underlying similarity between the fundamental properties of ordinary and dark matter particles. In this paper we generalise the previous analysis by considering a wider class of effective operators that non-gravitationally couple the ordinary and mirror sectors. We find that while all considered operators imply $\Omega_{Dark} =$ few$\times \Omega_B$, only a subset quantitatively reproduce the observed ratio $\Omega_B/\Omega_{Dark} \approx 0.20$. The $\sim 1$ eV mass scale induced through these operators hints at a connection with neutrino oscillation physics.

Phys.Rev. D69 (2004) 123510

Structure Formation with Mirror Dark Matter: CMB and LSS

Zurab Berezhiani, Paolo Ciarcelluti, Denis Comelli, Francesco L. Villante

In the mirror world hypothesis the mirror baryonic component emerges as a possible dark matter candidate. An immediate question arises: how the mirror baryons behave and what are the differences from the more familiar dark matter candidate, the cold dark matter (CDM)? In this paper we quantitatively answer this question and describe the implications on CMB and LSS. We need only two extra thermodynamical parameters to describe our model: the temperature of the mirror plasma(limited by the BBN) and the amount of mirror baryonic matter. We show as specific signatures on the evolution of the perturbations are related to the decoupling time and the dissipative Silk scale of the mirror baryons. Confronting with the present observational data, we also obtain some bounds on the mirror parameter space.

Int.J.Mod.Phys. D14 (2005) 107-119

Mirror World and its Cosmological Consequences

Zurab Berezhiani

We briefly review the concept of a parallel mirror' world which has the same particle physics as the observable world and couples to the latter by gravity and perhaps other very weak forces. The nucleosynthesis bounds demand that the mirror world should have a smaller temperature than the ordinary one. By this reason its evolution should substantially deviate from the standard cosmology as far as the crucial epochs like baryogenesis, nucleosynthesis etc. are concerned. In particular, we show that in the context of certain baryogenesis scenarios, the baryon asymmetry in the mirror world should be larger than in the observable one. Moreover, we show that mirror baryons could naturally constitute the dominant dark matter component of the Universe, and discuss its cosmological implications.

Int.J.Mod.Phys. A19 (2004) 3775-3806

Was ordinary matter synthesised from mirror matter? An attempt to explain why $\Omega_{Baryon} \approx 0.2\Omega_{Dark}$

R. Foot, R. R. Volkas

The cosmological dust has begun to settle. A likely picture is a universe comprised (predominantly) of three components: ordinary baryons ($\Omega_B \approx 0.05$), non-baryonic dark matter ($\Omega_{Dark} \approx 0.22$) and dark energy ($\Omega_{\Lambda} \approx 0.7$). We suggest that the observed similarity of the abundances of ordinary baryons and non-baryonic dark matter ($\Omega_{B}/\Omega_{Dark} \approx 0.20$) hints at an underlying similarity between the fundamental properties of ordinary and dark matter particles. This is necessarily the case if dark matter is identified with mirror matter. We examine a specific mirror matter scenario where $\Omega_B/\Omega_{Dark} \approx 0.20$ is naturally obtained.

Phys.Rev. D68 (2003) 021304

Mirror dark matter and large scale structure

A. Yu. Ignatiev, R. R. Volkas

Mirror matter is a dark matter candidate. In this paper, we re-examine the linear regime of density perturbation growth in a universe containing mirror dark matter. Taking adiabatic scale-invariant perturbations as the input, we confirm that the resulting processed power spectrum is richer than for the more familiar cases of cold, warm and hot dark matter. The new features include a maximum at a certain scale $\lambda_{max}$, collisional damping below a smaller characteristic scale $\lambda'_S$, with oscillatory perturbations between the two. These scales are functions of the fundamental parameters of the theory. In particular, they decrease for decreasing $x$, the ratio of the mirror plasma temperature to that of the ordinary. For $x \sim 0.2$, the scale $\lambda_{max}$ becomes galactic. Mirror dark matter therefore leads to bottom-up large scale structure formation, similar to conventional cold dark matter, for $x \stackrel{<}{\sim} 0.2$. Indeed, the smaller the value of $x$, the closer mirror dark matter resembles standard cold dark matter during the linear regime. The differences pertain to scales smaller than $\lambda'_S$ in the linear regime, and generally in the non-linear regime because mirror dark matter is chemically complex and to some extent dissipative. Lyman-$\alpha$ forest data and the early reionisation epoch established by WMAP may hold the key to distinguishing mirror dark matter from WIMP-style cold dark matter.

Phys.Rev. D68 (2003) 023518

The Early Mirror Universe: Inflation, Baryogenesis, Nucleosynthesis and Dark Matter

Zurab Berezhiani, Denis Comelli, Francesco L. Villante

There can exist a parallel mirror' world which has the same particle physics as the observable world and couples the latter only gravitationally. The nucleosynthesis bounds demand that the mirror sector should have a smaller temperature than the ordinary one. By this reason its evolution should be substantially deviated from the standard cosmology as far as the crucial epochs like baryogenesis, nucleosynthesis etc. are concerned. Starting from an inflationary scenario which could explain the different initial temperatures of the two sectors, we study the time history of the early mirror universe. In particular, we show that in the context of the GUT or electroweak baryogenesis scenarios, the baryon asymmetry in the mirror world should be larger than in the observable one and in fact the mirror baryons could provide the dominant dark matter component of the universe. In addition, analyzing the nucleosynthesis epoch, we show that the mirror helium abundance should be much larger than that of ordinary helium. The implications of the mirror baryons representing a kind of self-interacting dark matter for the large scale structure formation, the CMB anysotropy, the galactic halo structures, microlensing, etc. are briefly discussed.

Phys.Lett. B503 (2001) 362-375

Discovering mirror particles at the Large Hadron Collider and the implied cold universe

A. Yu. Ignatiev, R. R. Volkas

The Mirror Matter or Exact Parity Model sees every standard particle, including the physical neutral Higgs boson, paired with a parity partner. The unbroken parity symmetry forces the mass eigenstate Higgs bosons to be maximal mixtures of the ordinary and mirror Higgs bosons. Each of these mass eigenstates will therefore decay 50% of the time into invisible mirror particles, providing a clear and interesting signature for the Large Hadron Collider (LHC) which could thus establish the existence of the mirror world. However, for this effect to be observable the mass difference between the two eigenstates must be sufficiently large. In this paper, we study cosmological constraints from Big Bang Nucleosynthesis on the mass difference parameter. We find that the temperature of the radiation dominated (RD) phase of the universe should never have exceeded a few 10's of GeV if the mass difference is to be observable at the LHC. Chaotic inflation with very inefficient reheating provides an example of how such a cosmology could arise. We conclude that the LHC could thus discover the mirror world and simultaneously establish an upper bound on the temperature of the RD phase of the universe.

Phys.Lett. B487 (2000) 294-298

Mirror matter and primordial black holes

Nicole F. Bell, Raymond R. Volkas

A consequence of the evaporation of primordial black holes in the early universe may be the generation of mirror matter. This would have implications with regard to dark matter, and the number of light particle species in equilibrium at the time of big bang nucleosynthesis. The possibilities for the production of mirror matter by this mechanism are explored.

Phys.Rev. D59 (1999) 107301

Asymmetric Inflationary Reheating and the Nature of Mirror Universe

Z.G. Berezhiani, A.D. Dolgov, R.N. Mohapatra

The existence of a shadow world (or mirror universe) with matter and forces identical to that of the visible world but interacting with the latter only via gravity can be motivated by superstring theories as well as by recent attempts to understand the nature of a sterile neutrino needed if all known neutrino data are to be consistent with each other. A simple way to reconcile the constraints of big bang nucleosynthesis in such a theory is to postulate that the reheating temperature after inflation in the mirror universe is lower than that in the visible one. We have constructed explicit models that realize this proposal and have shown that the asymmetric reheating can be related to a difference of the electroweak symmetry breaking scales in the two sectors, which is needed for a solution of the neutrino puzzles in this picture. Cosmological implications of the mirror matter are also discussed.

Phys.Lett. B375 (1996) 26-36

Mirror baryons as the dark matter

Hardy M. Hodges

A "parallel world" with all of the standard particles, which primarily interacts gravitationally with our world, can be motivated via a symmetry principle designed to make a Lagrangian CP symmetric, while maintaining a CP asymmetry in the observable world. Such a symmetry is easily accommodated in grand unified theory models, and may also arise in superstring theories. The cosmological abundance of mirror particles is investigated after a period of chaotic inflation and subsequent reheating. Contrary to previous studies, I find that mirror and ordinary abundances may naturally be similar at the present epoch, and that mirror baryons can provide the closure density without violating nucleosynthesis constraints.

Phys. Rev. D 47 (1993) 456-459

Nucleosynthesis versus the mirror universe

Eric D. Carlson and S. L. Glashow

A mirror universe consisting of particles and forces isomorphic to ordinary particles and forces would couple to our universe only through gravity. Hypothetical particles displaying both types of forces would forge an additional link between the two universes. Due to radiative corrections, mirror particles would carry conventional charges of order $\epsilon e 10^{-3}$-$\epsilon e 10^{-6}$. This seems to offer a possible explanation of the anomalous observed value for the positronium decay rate [3]. However, $\epsilon<3\times 10^{-8}$ can be deduced from the successful standard model prediction of the primordial 4He abundance. A mirror-model explanation of the positronium anomaly is thereby ruled out, as is any other observable link to a hypothetical mirror universe.

Phys. Lett. B193 (1987) 168-170

Dark matter direct detection experiments:

Implications of the DAMA/NaI and CDMS experiments for mirror matter-type dark matter

R. Foot

We re-analyse the implications of the DAMA/NaI experiment for mirror matter-type dark matter, taking into account information from the energy dependence of the DAMA annual modulation signal. This is combined with the null results from the CDMS experiment, leading to fairly well defined allowed regions of parameter space. The allowed regions of parameter space will be probed in the near future by the DAMA/LIBRA, CDMS, and other experiments, which should either exclude or confirm this explanation of the DAMA/NaI annual modulation signal. In particular, we predict that the CDMS experiments should find a positive signal around the threshold recoil energy region, E_R < 15 keV in the near future.

Reconciling the positive DAMA annual modulation signal with the negative results of the CDMS II experiment

R. Foot

We examine the recent CDMS II results in the context of the mirror matter interpretation of the DAMA/NaI experiment.We find that the favoured mirror matter interpretation of the DAMA/NaI experiment -- a $He'/H'$ dominated halo with a small $O'$ component is fully consistent with the null results reported by CDMS II. While the CDMS II experiment is quite sensitive to a heavy $Fe'$ component, and may yet find a positive result, a more decisive test of mirror matter-type dark matter would require a lower threshold experiment using light target elements.

Mod.Phys.Lett. A19 (2004) 1841-1846

Exploring the mirror matter interpretation of the DAMA experiment: Has the dark matter problem been solved?

R. Foot

The self consistency between the impressive DAMA annual modulation signal and the differential energy spectrum is an important test for dark matter candidates.Mirror matter-type dark matter passes this test while other dark matter candidates, including standard (spin-independent) WIMPs and mini-electric charged particle dark matter, do not do so well.We argue that the unique properties of mirror matter-type dark matter seem to be just those required to fully explain the data, suggesting that the dark matter problem has finally been solved.

Implications of the DAMA and CRESST experiments for mirror matter-type dark matter

R. Foot

Mirror atoms are expected to be a significant component of the galactic dark matter halo if mirror matter is identified with the non-baryonic dark matter in the Universe. Mirror matter can interact with ordinary matter via gravity and via the photon-mirror photon kinetic mixing interaction -- causing mirror charged particles to couple to ordinary photons with effective electric charge $\epsilon e$. This means that the nuclei of mirror atoms can elastically scatter off the nuclei of ordinary atoms, leading to nuclear recoils, which can be detected in existing dark matter experiments. We show that the dark matter experiments most sensitive to this type of dark matter candidate (via the nuclear recoil signature) are the DAMA/NaI and CRESST/Sapphire experiments. Furthermore, we show that the impressive annual modulation signal obtained by the DAMA/NaI experiment can be explained by mirror matter-type dark matter for $|\epsilon | \sim 4 \times 10^{-9}$ and is supported by the CRESST/Sapphire data. This value of $|\epsilon |$ is consistent with the value obtained from various solar system anomalies including the Pioneer spacecraft anomaly, anomalous meteorite events and lack of small craters on the asteroid Eros. It is also consistent with standard BBN.

Phys.Rev. D69 (2004) 036001

Effects of mirror matter on (planetary) physics:

Have mirror micrometeorites been detected?

R. Foot, S. Mitra

Slow-moving ($v \sim 15$ km/s) 'dark matter particles' have allegedly been discovered in a recent experiment. We explore the possibility that these slow moving dark matter particles are small mirror matter dust particles originating from our solar system. Ways of further testing our hypothesis, including the possibility of observing these dust particles in cryogenic detectors such as NAUTILUS, are also discussed.

Phys.Rev. D68 (2003) 071901

Detecting mirror matter on Earth via its thermal imprint on ordinary matter

R. Foot, S. Mitra

Mirror matter type dark matter can exist on the Earth's surface, potentially in enhanced concentrations at various anomalous impact sites. Mirror matter fragments can draw in heat from the ordinary matter environment, radiate mirror photons and thereby cool the surrounding ordinary matter. We quantify this effect and suggest that it could be used to help locate mirror matter deposits. This method, together with the centrifuge technique, seems to provide the most promising means to experimentally detect mirror matter type dark matter in the Earth.

Phys.Lett. A315 (2003) 178-183

Detecting Dark Matter using Centrifuging Techniques

S. Mitra, R. Foot

A new and inexpensive technique for detecting self interacting dark matter in the form of small grains in bulk matter is proposed. Depending on the interactions with ordinary matter, dark matter grains in bulk matter may be isolated by using a centrifuge and using ordinary matter as a filter. The case of mirror matter interacting with ordinary matter via photon-mirror photon kinetic mixing provides a concrete example of this type of dark matter candidate.

Phys. Lett. B558 (2003) 9-14

Mirror matter in the Solar system: New evidence for mirror matter from Eros

R. Foot, S. Mitra

Mirror matter is an entirely new form of matter predicted to exist if mirror symmetry is a fundamental symmetry of nature. Mirror matter has the right broad properties to explain the inferred dark matter of the Universe and might also be responsible for a variety of other puzzles in particle physics, astrophysics, meteoritics and planetary science. It is known that mirror matter can interact with ordinary matter non-gravitationally via photon-mirror photon kinetic mixing. The strength of this possibly fundamental interaction depends on the (theoretically) free parameter $\epsilon$. We consider various proposed manifestations of mirror matter in our solar system examining in particular how the physics changes for different possible values of $\epsilon$. We find new evidence for mirror matter in the solar system coming from the observed sharp reduction in crater rates (for craters less than about 100 meters in diameter) on the asteroid 433 Eros. We also re-examine various existing ideas including the mirror matter explanation for the anomalous meteorite events, anomalous slow-down of Pioneer spacecraft etc.

Astropart. Phys. 19 (2003) 739-753

Ordinary atom-mirror atom bound states: A new window on the mirror world

R. Foot, S. Mitra

Mirror symmetry is a plausible candidate for a fundamental symmetry of particle interactions which can be exactly conserved if a set of mirror particles exist. The properties of the mirror particles seem to provide an excellent candidate to explain the inferred dark matter of the Universe and might also be responsible for a variety of other puzzles in particle physics, astrophysics, meteoritics and planetary science. One such puzzle -- the orthopositronium lifetime problem -- can be explained if there is a small kinetic mixing of ordinary and mirror photons. We show that this kinetic mixing implies the existence of ordinary atom - mirror atom bound states with interesting terrestrial and astrophysical implications. We suggest that sensitive mass spectroscopic studies of ordinary samples containing heavy elements such as lead might reveal the presence of these bound states, as they would appear as anomalously heavy elements. In addition to the effects of single mirror atoms, collective effects from embedded fragments of mirror matter (such as mirror iron microparticles) are also possible. We speculate that such mirror matter fragments might explain a mysterious UV photon burst observed coming from a laser irradiated lead target in a recent experiment.

Phys.Rev. D66 (2002) 061301

Exotic meteoritic phenomena: The Tunguska event and anomalous low altitude fireballs -- manifestations of the mirror world?

R. Foot, T. L. Yoon

There are a number of very puzzling meteoritic events including (a) The Tunguska event. It is the only known example of a low altitude atmospheric explosion. It is also the largest recorded event. Remarkably no fragments or significant chemical traces have ever been recovered. (b) Anomalous low altitude fireballs which (in some cases) have been observed to hit the ground. The absence of fragments is particularly striking in these cases, but this is not the only reason they are anomalous. On the other hand, there is strong evidence that most of our galaxy is made from exotic dark material - dark matter'. Mirror matter is one well motivated dark matter candidate, since it is dark and stable and it is required to exist if particle interactions are mirror symmetric. If mirror matter is the dark matter, then some amount must exist in our solar system. We demonstrate that the mirror matter theory allows for a simple explanation for the puzzling meteoritic events [both (a) and (b)] if they are due to mirror matter space-bodies. A direct consequence of this explanation is that mirror matter fragments should exist in (or on) the ground at various impact sites. The properties of this potentially recoverable material depend importantly on the sign of the photon-mirror photon kinetic mixing parameter, $\epsilon$. We argue that the broad characteristics of the anomalous events suggests that $\epsilon$ is probably negative. Strategies for detecting mirror matter in the ground are discussed.

Acta Phys.Polon. B33 (2002) 1979-2009

A mirror world explanation for the Pioneer spacecraft anomalies?

R. Foot, R. R. Volkas

We show that the anomalous acceleration of the Pioneer 10/11 spacecraft can be explained if there is some mirror gas or mirror dust in our solar system.

Phys.Lett. B517 (2001) 13-17

Mirror objects in the solar system?

Z. K. Silagadze

This talk was given at the Tunguska-2001 international conference but it is not about the Tunguska event. Instead we tried to give some flavor of mirror matter, which is predicted to exist if parity is an unbroken symmetry of nature, to non-experts. The possible connection of the mirror matter ideas to the Tunguska phenomenon was indicated by Foot and Gninenko some time ago and was elaborated by Foot in the separate talk at this conference. If the mirror world interpretation of the Tunguska like events is indeed correct then the most fascinating (but very speculative) possibility is that some well known celestial bodies with strange properties are in fact made mostly from mirror matter, and so maybe the mirror world was discovered long ago and we just have not suspected this.

Acta Phys.Polon. B33 (2002) 1325-1341

The mirror world interpretation of the 1908 Tunguska event and other more recent events

R. Foot

Mirror matter is predicted to exist if parity (i.e. left-right symmetry) is a symmetry of nature. Remarkably mirror matter is capable of simply explaining a large number of contemporary puzzles in astrophysics and particle physics including: Explanation of the MACHO gravitational microlensing events, the existence of close-in extrasolar gas giant planets, apparently isolated' planets, the solar, atmospheric and LSND neutrino anomalies, the orthopositronium lifetime anomaly and perhaps even gamma ray bursts. One fascinating possibility is that our solar system contains small mirror matter space bodies (asteroid or comet sized objects), which are too small to be revealed from their gravitational effects but nevertheless have explosive implications when they collide with the Earth. We examine the possibility that the 1908 Tunguska explosion in Siberia was the result of the collision of a mirror matter space body with the Earth. We point out that if the catastrophic event and many other similar smaller events are manifestations of the mirror world then these impact sites should be a good place to start digging for mirror matter. Mirror matter could potentially be extracted and purified using a centrifuge and have many useful industrial applications.

Acta Phys.Polon. B32 (2001) 3133

Orthopositronium:

An apparatus to search for mirror dark matter via the invisible decay of orthopositronium in vacuum

A.Badertscher, A. Belov, P. Crivelli, M. Felcini, W. Fetscher, S.N. Gninenko, N.A. Golubev, M.M. Kirsanov, L.L. Kurchaninov, J.P. Peigneux, A. Rubbia, D. Sillou

Mirror matter is a possible dark matter candidate. It is predicted to exist if parity is an unbroken symmetry of the vacuum. The existence of the mirror matter, which in addition to gravity is coupled to our world through photon-mirror photon mixing, would result in orthopositronium (o-Ps) to mirror orthopositronium (o-Ps') oscillations. The experimental signature of this effect is the invisible decay of o-Ps in vacuum. This paper describes the design of the new experiment for a search for the o-Ps -> invisible decay in vacuum with a sensitivity in the branching ratio of Br(o-Ps -> invisible)\simeq 10^{-7}, which is an order of magnitude better than the present limit on this decay mode from the Big Bang Nucleosynthesis. The experiment is based on a high-efficiency pulsed slow positron beam, which is also applicable for other experiments with o-Ps, and (with some modifications) for applied studies. Details of the experimental design and of a new pulsing method, as well as preliminary results on requirements for the pulsed beam components are presented. The effects of o-Ps collisions with the cavity walls as well as the influence of external fields on the o-Ps to o-Ps' oscillation probability are also discussed.

Int.J.Mod.Phys. A19 (2004) 3833-3848

Can the mirror world explain the ortho-positronium lifetime puzzle?

R. Foot, S. N. Gninenko

We suggest that the discrepant lifetime measurements of ortho-positronium can be explained by ortho-positronium oscillations into mirror ortho-positronium. This explanation can be tested in future vacuum experiments.

Phys.Lett. B480 (2000) 171-175

Positronium versus the mirror universe

S. L. Glashow

A mirror universe of fermions and forces isomorphic to but distinct from those we see couples directly to our universe only by gravity. Particles at any mass scale enjoying both normal and shadow forces forge an electromagnetic link (by radiative corrections) between the two universes such that mirror particles display conventional electric charges 10-3-10-5 e. This produces mixing between triplet positronium and its analogous mirror state through a one-photon annihilation diagram. Consequent effects are contrary to experiment. The possible existence of such a mirror universe is thereby excluded.

Phys. Lett. B167 (1986) 35-36

Neutrinos:

Mirror model for sterile neutrinos

Veniamin Berezinsky, Mohan Narayan, Francesco Vissani

Sterile neutrinos are studied as subdominant contribution to solar neutrino physics. The mirror-matter neutrinos are considered as sterile neutrinos. We use the symmetric mirror model with gravitational communication between mirror and visible sectors. This communication term provides mixing between visible and mirror neutrinos with the basic scale mu=v^2/M_Pl=5*10^-6 eV, where v=174 GeV is the vacuum expectation value of the standard electroweak group and M_Pl is the Planckian mass. It is demonstrated that each mass eigenstate of active neutrinos splits into two states separated by small Delta m^2. Unsuppressed oscillations between active and sterile neutrinos nu_a --> nu_s occur only in transitions between each of these close pairs (windows''). These oscillations are characterized by very small Delta m^2 and can suppress the flux and distort spectrum of pp-neutrinos in detectable way. The other observable effect is anomalous seasonal variation of neutrino flux, which appears in LMA solution. The considered subdominant neutrino oscillations nu_a <--> nu_s can reveal itself as big effects in observations of supernova neutrinos and high energy (HE) neutrinos. In the case of HE neutrinos they can provide a very large diffuse flux of active neutrinos unconstrained by the e-m cascade upper limit.

Nucl.Phys. B658 (2003) 254-280

Mirror matter and heavy singlet neutrino oscillations in the early universe

Nicole F. Bell

We investigate the mixing of heavy gauge singlet neutrinos in a mirror matter model employing the seesaw mechanism. The parameter constraints that must be satisfied to prevent the overproduction of mirror matter in the early universe are deduced. We find that no fine tuning in the heavy neutral fermion sector is required for this mirror matter model to satisfy cosmological constraints. Baryogenesis scenarios are briefly discussed in the context of the mirror model.

Phys.Lett. B479 (2000) 257-264

Mirror Neutrinos and the Early Universe

Raymond R Volkas

I review the construction of the Exact Parity or Mirror Matter Model and explain how it solves the solar and atmospheric neutrino problems. The oscillation driven relic neutrino asymmetry amplification phenomenon is then used to demonstrate the consistency of the model with Big Bang Nucleosynthesis.

Invited talk at COSMO 99: 3rd International Conference on Particle Physics and the Early Universe, Trieste, Italy, 27 Sep - 3 Oct 1999.

Neutrino mass and mirror universe

Z.K. Silagadze

The existence of the mirror world, with the same microphysics as our own one but with opposite P-asymmetry, not only restores an exact equivalence between left and right but also naturally explains, via a see-saw like mechanism, why the neutrino is ultralight.

Phys.Atom.Nucl. 60 (1997) 272-275; Yad.Fiz. 60N2 (1997) 336-339

Ultra High Energy Cosmic Rays:

Neutron - Mirror Neutron Oscillation and Ultra High Energy Cosmic Rays

Zurab Berezhiani, Luis Bento

We discuss the phenomenological and astrophysical implications of neutron - mirror neutron oscillation and show that the present experimental data allow an oscillation time in vacuum much smaller than the neutron lifetime. Such a fast oscillation could provide a very efficient mechanism for transporting protons with super-GZK energies at very large distances provided that the CMB of mirror photons has a temperature T' about 3 times smaller than that of ordinary photons, T, in agreement with primordial nucleosynthesis (x = T'/T < 0.5). The mechanism operates as follows: a super-GZK energy proton scatters a CMB photon producing a neutron that oscillates into a mirror neutron which in turn decays into a mirror proton. The latter undergoes a symmetric process producing back an ordinary nucleon but only after traveling a distance x^{-3} times larger than ordinary protons. This may relax or completely remove the GZK-cutoff in the cosmic ray energy spectrum and also explain the correlation between the observed UHE protons and far distant sources like BL Lacs.

Neutron -- Mirror Neutron Oscillation: How Fast Might It Be?

Zurab Berezhiani, Luis Bento

We discuss the phenomenological implications of the neutron ($n$) oscillation into the mirror neutron ($n'$), a hypothetical particle from a parallel mirror world, exactly degenerate in mass with the neutron but sterile to normal matter. We show that the present experimental data allow a maximal $n-n'$ oscillation in vacuum with a characteristic time $\tau_{nn'}$ much shorter than the neutron lifetime, in fact as small as 1 sec, which corresponds to a mass mixing $\delta m = \tau^{-1}_{nn'} \sim 10^{-15}$ eV between $n$ and $n'$ states. This phenomenon may manifest in neutron disappearance oscillation experiments perfectly accessible to present experimental capabilities and may also have significant astrophysical consequences, in particular for the propagation of ultra high energy cosmic rays.

Supernova explosions, gamma ray bursts etc.:

Supernova explosions, 511 keV photons, gamma ray bursts and mirror matter

R. Foot, Z. K. Silagadze

There are three astroparticle physics puzzles which fire the imagination: the origin of the Great Positron Producer'' in the galactic bulge, the nature of the gamma-ray bursts central engine and the mechanism of supernova explosions. We show that the mirror matter model has the potential to solve all three of these puzzles in one beautifully simple strike.

Int.J.Mod.Phys. D14 (2005) 143-151

Mirror World and Axion: Relaxing Cosmological Bounds

Giannotti Maurizio

The cosmological (upper) limit on the Peccei-Quinn constant, related to the primordial oscillations of the axion field, can be relaxed for a mirror axion model. The simple reason is that the mirror world is colder and so the behavior of the axion temperature-dependent mass is dominated by the contribution from the mirror sector. So the coherent oscillations start earlier and correspondingly the axion mass density \Omega_a h^2 is reduced.

Int.J.Mod.Phys. A20 (2005) 2454-2458

Mirror World, Supersymmetric Axion and Gamma Ray Bursts

L. Gianfagna, M. Giannotti, F. Nesti

A modification of the relation between axion mass and the PQ constant permits a relaxation of the astrophysical constraints, considerably enlarging the allowed axion parameter space. We develop this idea in this paper, discussing a model for an {\it ultramassive} axion, which essentially represents a supersymmetric Weinberg-Wilczek axion of the mirror world. The experimental and astrophysical limits allow a PQ scale f_a ~ 10^4-10^6 GeV and a mass m_a ~ 1MeV, which can be accessible for future experiments. On a phenomenological ground, such an {\it ultramassive} axion turns out to be quite interesting. It can be produced during the gravitational collapse or during the merging of two compact objects, and its subsequent decay into e+e- provides an efficient mechanism for the transfer of the gravitational energy of the collapsing system to the electron-positron plasma. This could resolve the energy budget problem in the Gamma Ray Bursts and also help in understanding the SN type II explosion phenomena.

JHEP 0410 (2004) 044

Strong CP problem and mirror world: the Weinberg Wilczek axion revisited

Zurab Berezhiani, Leonida Gianfagna, Maurizio Giannotti

A new possibility for solving the strong CP-problem is suggested,which assumes that apart of the ordinary world of observable particles described by standard model, there exits a mirror sector of particles and two sectors share the same Peccei-Quinn symmetry realized {\it a l\a} Weinberg-Wilczek model. The mirror gauge group is completely analogous to that of the standard model for ordinary particles but having somewhat larger electroweak scale,which in turn implies the infrared scale $\Lambda'$ of the mirror strong interactions has to be larger than the ordinary QCD scale $\Lambda$. In this way, the axion mass and interaction constants are actually determined by mirror sector scales $v'$ and $\Lambda'$, while the $\theta$ terms are simultaneously cancelled in both sectors due to mirror symmetry. The experimental and astrophysical limits on such an axion is discussed. An interesting parameter window is found where $f_a \sim {\rm few}\times 10^4$ GeV whereas the axion mass is $\sim 1$ MeV.

Phys.Lett. B500 (2001) 286-296

Cosmic Gamma-ray Bursts. Lectures Presented at XXVII ITEP Winter School

S.Blinnikov (ITEP and SAI, Moscow)

The properties of the cosmic Gamma-ray Bursts (GRBs) are briefly summarized. A detailed bibliography is given with titles of the papers. Two fundamental theoretical problems are pointed out: the problem of the energy source, and the problem of compactness. I demonstrate some inconsistencies in the estimates of the fireball optical thickness that are widely used in the discussion of the latter problem. The possible connection of GRBs with the Dark Matter candidates is mentioned. I argue that GRBs can be produced by collapses or mergers of stars made of one probable Dark Matter candidate, namely the mirror particles. I speculate on the impact that the parameters of the neutrino oscillations might have on the observed properties of GRBs if the latter are the products of mirror star deaths.

Surveys High Energ.Phys. 15 (2000) 37-74

Gamma-ray Bursts Produced by Mirror Stars

S. Blinnikov (ITEP nad SAI, Moscow)

I argue that cosmic Gamma-ray Bursts (GRB) may be produced by collapses or mergers of stars made of mirror' matter. The mirror neutrinos (which are sterile for our matter) produced at these events can oscillate into ordinary neutrinos. The annihilations or decays of the latter create an electron-positron plasma and subsequent relativistic fireball with a very low baryon load needed for GRBs. The concept of mirror matter is able to explain several key problems of modern astrophysics: neutrino anomalies, the missing mass, MACHO microlensing events and GRBs. Thus this concept becomes very appealing and should be considered quite seriously and attentively.

Presented at XXVII ITEP Winter School, Snegiri, Feb. 16 -- 24, 1999

Mirror World versus large extra dimensions

Z.K. Silagadze

Recently proposed low scale quantum gravity scenario is expected to have a significant impact on the Mirror World hypothesis. Some aspects of this influence is investigated here, assuming that the fundamental gravity scale is near a TeV. It is shown that future colliders will be capable to produce the mirror matter, but an experimental signature, which will distinguish such events from the background, is unclear. The smoking gun'' signals of the Mirror World would be an observation of decays like $\Upsilon(2S)\to \tilde \chi_{b2} \gamma$. But unfortunately the expected branching ratios are very small. Finally, it is shown that a mirror supernova will be quite a spectacular event for our world too, because a considerable amount of ordinary energy is expected to be emitted in the first several seconds.

Mod.Phys.Lett. A14 (1999) 2321-2328

Matter-affected neutrino oscillations in ordinary and mirror stars and their implications for gamma-ray bursts

Raymond R. Volkas, Yvonne Y. Y. Wong

It has been proposed that the annihilation process $\nu\bar{\nu} \to e^{-}e^{+} \to \gamma\gamma$ may be responsible for the generation of gamma-ray bursts (GRBs). The incipient neutrino--antineutrino pairs carry virtually all of the gravitational binding energy available from the central engine. However, gamma-ray bursters proposed to date are inevitably surrounded by an excess of baryons, leading to the "baryon-loading problem". In the light of growing evidence for neutrino oscillations, we discuss the implications of matter-affected oscillations for GRB energetics, and on the viability of "mirror" stars as GRB progenitors.

Astropart.Phys. 13 (2000) 21-30

Mirror planets, mirror stars etc.:

Evolutionary and structural properties of mirror star MACHOs

Zurab Berezhiani, Santi Cassisi, Paolo Ciarcelluti, Adriano Pietrinferni

There can exist a hidden sector of the Universe in the form of parallel ''mirror'' world which has the same particle physics as the observable world and interacts with the latter only gravitationally. Big Bang Nucleosynthesis bounds demand that the mirror sector should have a smaller temperature than the ordinary one. This implies that the mirror matter could play a role of dark matter, and in addition its chemical content should be dominated by helium. Here we study the evolutionary and structural properties of the mirror stars which essentially are similar to that of the ordinary stars but with higher helium contents. Being invisible in terms of photons, they could be observed only as MACHOs in the microlensing experiments. Using a numerical code, we compute evolution of stars with large helium abundances (Y = 0.30-0.80) and a wide range of masses, from 0.5 to 10 solar masses. We found that helium dominated mirror star should have much faster evolutionary time (up to a factor 30) than the ordinary star with the same mass. In addition, we show the diagrams of luminosities, effective temperatures, central temperatures and densities, and compute the masses of the He core at ignition and the minimum mass for carbon ignition, for different chemical compositions. The general conclusion is that mirror stars evolve faster as compared to ordinary ones, and explode earlier as type II supernovae, thus enriching the galactic halo of processed mirror gas with higher metallicity, with implications for MACHO observations and galaxy evolution.

Testing the mirror world hypothesis for the close-in extrasolar planets

R. Foot

Because planets are not expected to be able to form close to stars due to the high temperatures, it has been suggested that the observed close orbiting ($\sim 0.05$ AU) large mass planets ($\sim M_J$) might be mirror worlds -- planets composed predominately of mirror matter. The accretion of ordinary matter onto the mirror planet (from e.g. the solar wind from the host star) will make the mirror planet opaque to ordinary radiation with an effective radius $R_p$. It was argued in a previous paper, astro-ph/0101055, that this radius was potentially large enough to explain the measured size of the first transiting close-in extrasolar planet, HD209458b. Furthermore, astro-ph/0101055, made the rough prediction: $R_p \propto \sqrt{{T_s \over M_p}}$, where $T_s$ is the surface temperature of the ordinary matter in the mirror planet and $M_p$ is the mass of the planet (the latter dependence being the more robust prediction). We compare this prediction with the recently discovered transiting planets, OGLE-TR-56b and OGLE-TR-113b.

Acta Phys.Polon. B35 (2004) 2473-2478

Do mirror planets exist in our solar system?

R. Foot, Z. K. Silagadze

Mirror matter is predicted to exist if parity is an unbroken symmetry of nature. Currently, there is a large amount of evidence that mirror matter actually exists coming from astrophysics and particle physics. One of the most fascinating (but speculative) possibilities is that there is a significant abundance of mirror matter within our solar system. If the mirror matter condensed to form a large body of planatary or stellar mass then there could be interesting observable effects. Indeed studies of long period comets suggest the existence of a solar companion which has escaped direct detection and is therefore a candidate for a mirror body. Nemesis, hypothetical "death star" companion of the Sun, proposed to explain biological mass extinctions, may potentially be a mirror star. We examine the prospects for detecting these objects if they do indeed exist and are made of mirror matter.

Acta Phys.Polon. B32 (2001) 2271-2278

Are mirror planets opaque?

R. Foot

Over the last few years, many close orbiting ($\sim 0.05$ A.U.) large mass planets ($\sim M_{J}$) of nearby stars have been discovered. Their existence has been inferred from tiny Doppler shifts in the light from the star and in one case a transit has been observed. Because ordinary planets are not expected to be able to form this close to ordinary stars due to the high temperatures, it has been speculated that the close-in large planets are in fact exotic heavenly bodies made of mirror matter. We show that the accretion of ordinary matter onto the mirror planet (from e.g.the solar wind from the host star) should make the mirror planet opaque to ordinary radiation with an effective radius ($R_p$) large enough to explain the measured size of the transiting close-in extrasolar planet, HD209458b. Furthermore we obtain the rough prediction that $R_{p} \propto \sqrt{{T_s\over M_p}}$ (where $T_s$, is the surface temperature of the ordinary matter in the mirror planet and $M_p$ is the mass of the mirror planet) which will be tested in the near future as more transiting planets are found. We also show that the mirror world interpretation of the close-in extra solar planets explains the low albedo of $\tau$ Boo b because the large estimated mass of $\tau$ Boo b ($\sim 7M_J$) implies a small effective radius of $R_p \approx 0.5R_J$ for $\tau$ Boo.

Phys.Lett. B505 (2001) 1-5

Have mirror planets been observed?

R. Foot

Over the last few years, several close orbiting ($\sim 0.05$ AU) large mass planets ($M \sim M_{Jupiter}$) of nearby stars have been discovered. Their existence has been inferred from tiny doppler shifts in the light from the star. We suggest that these planets may be made of mirror matter. We also suggest that some stars such as our sun may have a similar amount of mirror matter which has escaped detection.

Phys.Lett. B471 (1999) 191-194

Have mirror stars been observed?

R. Foot

Observations by the MACHO collaboration suggest that a significant proportion of the galactic halo dark matter is in the form of compact objects with typical masses $M\sim 0.5M_{\odot}$. One of the current mysteries is the nature and origin of these objects. We suggest that these objects are stars composed of mirror matter. This interpretation provides a plausible explanation for the inferred masses and abundance of the MACHO events. We also comment on the possibility of inferring the existence of mirror supernova's by detecting the neutrino burst in existing underground detectors such as SuperKamiokande.

Phys.Lett. B452 (1999) 83-86

A quest for weak objects and for invisible stars

S.I.Blinnikov

High quality spectra to be produced by SUBARU 8 meter telescope will be extremely valuable for numerous astronomical projects. Here I concentrate on two classical types of weak broad line objects -- distant supernovae and white dwarfs -- with emphasis of their importance for fundamental physics, not only for astronomy. With regard to recent results of MACHO experiment and HST weak star counts I discuss one exotic possibility: invisible stars made of the so called mirror'' matter.

presented at "Baryonic Matter in the Universe and Its Spectroscopic Studies" (November 22 - 24, 1996, Atami, Japan)

Observational Physics of Mirror World

M. Yu. Khlopov, G. M. Beskin, N. E. Bochkarev, L. A. Pushtilnik, S. A. Pushtilnik

Sov.Astron.35:21,1991; Astron.Zh.Akad.Nauk CCCP 68:42-57,1991

Reviews:

Through the Looking-Glass: Alice's Adventures in Mirror World

Zurab Berezhiani

We briefly review the concept of a parallel mirror' world which has the same particle physics as the observable world and couples to the latter by gravity and perhaps other very weak forces. The nucleosynthesis bounds demand that the mirror world should have a smaller temperature than the ordinary one. By this reason its evolution should substantially deviate from the standard cosmology as far as the crucial epochs like baryogenesis, nucleosynthesis etc. are concerned. In particular, we show that in the context of certain baryogenesis scenarios, the baryon asymmetry in the mirror world should be larger than in the observable one. Moreover, we show that mirror baryons could naturally constitute the dominant dark matter component of the Universe, and discuss its cosmological implications.

Ian Kogan Memorial Collection "From Fields to Strings: Circumnavigating Theoretical Physics", Eds. M. Shifman et al., World Scientific, Singapore, vol. 3, pp. 2147-2195

Mirror matter-type dark matter

R. Foot

There are six main things which any non-baryonic dark matter theory should endeavour to explain: (1) The basic dark matter particle properties [mass, stability, darkness]; (2) The similarity in cosmic abundance between ordinary and non-baryonic dark matter, $\Omega_B \sim \Omega_{dark}$; (3) Large scale structure formation; (4) Microlensing (MACHO) events; (5) Asymptotically flat rotation curves in spiral galaxies; (6) The impressive DAMA/NaI annual modulation signal. Only mirror matter-type dark matter is capable of explaining all six of these desirable features. The purpose of this article is to provide an up-to-date and pedagogical review of this dark matter candidate.

Int.J.Mod.Phys. D13 (2004) 2161-2192

Mirror World and its Cosmological Consequences

Zurab Berezhiani

We briefly review the concept of a parallel mirror' world which has the same particle physics as the observable world and couples to the latter by gravity and perhaps other very weak forces. The nucleosynthesis bounds demand that the mirror world should have a smaller temperature than the ordinary one. By this reason its evolution should substantially deviate from the standard cosmology as far as the crucial epochs like baryogenesis, nucleosynthesis etc. are concerned. In particular, we show that in the context of certain baryogenesis scenarios, the baryon asymmetry in the mirror world should be larger than in the observable one. Moreover, we show that mirror baryons could naturally constitute the dominant dark matter component of the Universe, and discuss its cosmological implications.

Int.J.Mod.Phys. A19 (2004) 3775-3806

Experimental implications of mirror matter-type dark matter

R. Foot

Mirror matter-type dark matter is one dark matter candidate which is particularly well motivated from high energy physics. The theoretical motivation and experimental evidence are pedagogically reviewed, with emphasis on the implications of recent orthopositronium experiments, the DAMA/NaI dark matter search, anomalous meteorite events etc.

Int.J.Mod.Phys. A19 (2004) 3807-3818

Mirror matter

A.Yu.Ignatiev, R.R.Volkas

One of the deepest unsolved puzzles of subatomic physics is why Nature prefers the left particles to the right ones. Mirror matter is an attempt to understand this mystery by assuming the existence of a "parallel''world where this preference is exactly opposite. Thus in the Universe consisting of the ordinary and the mirror matter the symmetry between the left and right is completely restored. Mirror matter is constrained to interact with us only very weakly. Still, its existence can be inferred by using experimental evidence such as the observation of astrophysical objects related to the dark matter (MACHO), neutrino physics and other sources. This talk will focus on several key aspects of mirror matter physics including the possible existence of mirror matter inside the Earth and the suggestion that the recently observed "isolated" planets may in fact be orbiting around mirror stars.

Talk given by A.Yu.Ignatiev at the 15th Biennual Congress of the Australian Institute of Physics (Sydney, July 2002)

Does mirror matter exist?

R. Foot

One of the most fascinating ideas coming from particle physics is the concept of mirror matter. Mirror matter is a new form of matter which is predicted to exist if mirror symmetry is respected by nature. At the preset time evidence that mirror matter actually exists is in abundance, coming from a range of observations and experiments in astronomy, particle physics, meteoritics and planetary science.

Seven (and a half) reasons to believe in Mirror Matter: From neutrino puzzles to the inferred Dark matter in the Universe

R. Foot

Parity and time reversal are obvious and plausible candidates for fundamental symmetries of nature. Hypothesising that these symmetries exist implies the existence of a new form of matter, called mirror matter. The mirror matter theory (or exact parity model) makes four main predictions: 1) Dark matter in the form of mirror matter should exist in the Universe (i.e. mirror galaxies, stars, planets, meteoroids...), 2) Maximal ordinary neutrino - mirror neutrino oscillations if neutrinos have mass, 3) Orthopositronium should have a shorter effective lifetime than predicted by QED (in "vacuum" experiments) because of the effects of photon-mirror photon mixing and 4) Higgs production and decay rate should be 50% lower than in the standard model due to Higgs mirror - Higgs mixing (assuming that the seperation of the Higgs masses is larger than their decay widths). At the present time there is strong experimental/observational evidence supporting the first three of these predictions, while the fourth one is not tested yet because the Higgs boson, predicted in the standard model of particle physics, is yet to be found. This experimental/observational evidence is rich and varied ranging from the atmospheric and solar neutrino deficits, MACHO gravitational microlensing events, strange properties of extra-solar planets, the existence of "isolated" planets, orthopositronium lifetime anomaly, Tunguska and other strange "meteor" events including perhaps, the origin of the moon. The purpose of this article is to provide a not too technical review of these ideas along with some new results.

Acta Phys.Polon. B32 (2001) 2253-2270

TeV scale gravity, mirror universe, and ... dinosaurs

Z.K. Silagadze

This is somewhat extended version of the talk given at the Gran Sasso Summer Institute: Massive Neutrinos in Physics and Astrophysics. It describes general ideas about mirror world, extra spatial dimensions and dinosaur extinction. Some suggestions are made how these seemingly different things can be related to each other.

Acta Phys.Polon. B32 (2001) 99-128

Theory:

Mirror World at the Large Hadron Collider

Riccardo Barbieri, Thomas Gregoire, Lawrence J. Hall

A mirror world can modify in a striking way the LHC signals of the Higgs sector. An exact or approximate Z_2 symmetry between the mirror world and our world allows large mixing between the Higgs bosons of these worlds, leading to production rates and branching ratios for these states that are markedly different from the standard model and are characteristic of a mirror world. The constraints on these Higgs boson masses from precision electroweak data differ from the standard model bound, so that the new physics that cancels the quadratic divergence induced by the top quark may appear at a larger scale, possibly beyond the reach of the LHC. However, the scale of new physics needed to cancel the quadratic divergence induced by the Higgs boson is not significantly changed. With small breakings of the Z_2 parity, the lightest mirror quarks (and possibly charged mirror leptons) could be the dark matter in the universe, forming galactic halos that are stable to cooling. A possible signal from the relic radiation density of the mirror world is also discussed.

Generalized mirror matter models

R. Foot

Non-minimal gauge models with exact unbroken improper space-time symmetries are constructed and their cosmological and astrophysical implications explored.

Domain walls in noncommutative gauge theories, folded D-branes, and communication with mirror world

S.L. Dubovsky, S.M. Sibiryakov

Noncommutative U(N) gauge theories at different N may be often thought of as different sectors of a single theory. For instance, U(1) theory possesses a sequence of vacua labeled by an integer parameter N, and the theory in the vicinity of the N-th vacuum coincides with the U(N) noncommutative gauge theory. We construct domain walls on noncommutative plane, which separate vacua with different gauge groups in gauge theory with adjoint scalar field. The scalar field has nonminimal coupling to the gauge field, such that the scale of noncommutativity is determined by the vacuum value of the scalar field. The domain walls are solutions of the BPS equations in the theory. It is natural to interprete the domain wall as a stack of D-branes plus a stack of folded D-branes. We support this interpretation by the analysis of small fluctuations around domain walls, and suggest that such configurations of branes emerge as solutions of the Matrix model in large class of pp-wave backgrounds with inhomogeneous field strength. We point out that the folded D-brane per se provides an explicit realization of the "mirror world" idea, and speculate on some phenomenological consequences of this scenario.

Nucl.Phys. B691 (2004) 91-110

Physics of mirror photons

R. Foot, A. Yu. Ignatiev, R. R. Volkas

The physics of kinetic mixing between ordinary and mirror photons is discussed. An important role is played by four linear combinations we dub the physical photon, the sterile photon, the physical mirror photon, and the sterile mirror photon. Because of the mass degeneracy between the two gauge bosons, quantum coherence effects are important. The physical photon becomes a certain coherent superposition of the bare ordinary photon and the bare mirror photon. Similarly, the physical mirror photon is another, but {\it not orthogonal}, coherent superposition. We discuss the physics of the interaction between physical mirror photons and ordinary matter. Observational signatures for some hybrid ordinary/mirror binary astrophysical systems are qualitatively discussed. We show that a small amount of ordinary matter at the center of a mirror star may make the mirror star observable. We speculate that the recently reported halo white dwarfs might actually be mirror halo stars.

Phys.Lett. B503 (2001) 355-361

External Inversion, Internal Inversion, and Reflection Invariance

Matej Pavsic

Having in mind that physical systems have different levels of structure we develop the concept of external, internal and total improper Lorentz transformation (space inversion and time reversal). A particle obtained from the ordinary one by the application of internal space inversion or time reversal is generally a different particle. From this point of view the intrinsic parity of a nuclear particle (elementary particle') is in fact the external intrinsic parity, if we take into account the internal structure of a particle. We show that non-conservation of the external parity does not necessarily imply non-invariance of nature under space inversion. The conventional theory of beta-decay can be corrected by including the internal degrees of freedom to become invariant under total space inversion, though not under the external one.

Int.J.Theor.Phys. 9 (1974) 229-244

Talks:

Lev Okun:

Spacetime and Vacuum as seen from Moscow

listen or

download text

Websites:

Robert Foot's webpage

First Prize for Mirror Matter Project