A model of inhomogeneous baryogenesis based on the Affleck and Dine mechanism is described. A simple coupling of the scalar baryon field to the inflaton allows for formation of astronomically significant bubbles with a large baryon (or antibaryon) asymmetry. During the farther evolution these domains form compact stellar-like objects, or lower density clouds, or primordial black holes of different size. According to the scenario, such high baryonic number objects occupy relatively small fraction of space but despite that they may significantly contribute to the cosmological mass density. For some values of parameters the model allows the possibility the whole dark matter in the universe to be baryonic. Furthermore, the model allows the existence of the antibaryonic B-bubbles, i.e. a significant fraction of the mass density in the universe can be in the form of the compact antimatter objects (e.g. anti-stars).
Possible mechanisms of abundant creation of antimatter in the universe are reviewed. The necessary conditions for that are: baryonic charge nonconservation, spontaneous breaking of charge symmetry or nonequilibrium initial state, and the formation of appropriate initial conditions during inflation. In this case the universe may be populated with domains, cells, or even stellar size objects consisting of antimatter.
Although the origin of matter-antimatter asymmetry remains unknown, continuing advances in theory and improved experimental limits have ruled out some scenarios for baryogenesis, for example the sphaleron baryogenesis at the electroweak phase transition in the standard model. At the same time, the success of cosmological inflation and the prospects for discovering supersymmetry at the LHC have put some other models in sharper focus. We review the current state of our understanding of baryogenesis with the emphasis on those scenarios that we consider most plausible.
Possible mechanisms of baryogenesis are reviewed. Special attention is payed to those which allow for creation of astronomically significant domains or objects consisting of antimatter. Observational manifestations of cosmological antimatter are discussed.
Models of baryogenesis which may lead to astronomically significant amount of antimatter in the universe are reviewed. Observational features are briefly discussed.
We review the production of the matter-antimatter asymmetry in the early Universe, that is baryogenesis, in out-of-equlibrium conditions induced by decays of heavy particles or by the presence of phase boundaries. The most prominent examples are given by leptogenesis and electroweak baryogenesis, respectively. For both cases, we derive the equations that govern the production of the asymmetries. We first use intuitive arguments based on classical fluid equations in combination with quantum-field-theoretical effects of CP-violation. As for a more thorough approach that is well-suited for system…
Different scenarios of baryogenesis are briefly reviewed from the point of view of possibility of generation of cosmologically interesting amount of antimatter. It is argued that creation of antimatter is possible and natural in many models. In some models not only anti-helium may be produced but also a heavier anti-elements and future observations of the latter would be critical for discovery or establishing stronger upper limits on existence of antimatter. Incidentally a recent observation of iron-rich quasar may present a support to one special model of antimatter creation.
Primordial nucleosynthesis calculations are shown to be able to provide constraints on electroweak baryogenesis which produce a highly inhomogeneous distribution of the baryon-to-photon ratio. Such baryogenesis scenarios overproduce 4He and/or 7Li and can be ruled out whenever a fraction f<3*10e-6(100 GeV/T)^3 of nucleated bubbles of broken-symmetry phase contributes > 10% of the baryon number within the horizon volume.
Properties of neutrinos, the lightest of all elementary particles, may be the origin of the entire matter-antimatter asymmetry of the universe. This requires that neutrinos are Majorana particles, which are equal to their antiparticles, and that their masses are sufficiently small. Leptogenesis, the theory explaining the cosmic matter-antimatter asymmetry, predicts that all neutrino masses are smaller than 0.2 eV, which will be tested by forthcoming laboratory experiments and by cosmology.
In the presence of background fields that spontaneously violate Lorentz invariance, a matter-antimatter asymmetry can be generated even in thermal equilibrium. In this paper we systematically investigate models of this type, showing that either high-energy or electroweak versions of baryogenesis are possible, depending on the dynamics of the Lorentz-violating fields. In addition to the previously-studied models of spontaneous baryogenesis and quintessential baryogenesis, we identify two scenarios of interest: baryogenesis from a pseudo-Nambu-Goldstone boson with weak-scale mass and intermediat…
The possibility of creation of cosmologically significant antimatter are analyzed in different scenarios of baryogenesis. It is argued that there may exist plenty of antimatter even in our Galaxy. Possible forms of antimatter objects and their observational signatures are discussed.
We investigate the influence of primordial perturbations of the energy density and space--time metric on the generation of the lepton and baryon asymmetries. In the weak and strong washout regimes baryon isocurvature perturbations with amplitudes of the same order as those of the CMB perturbations are generated on scales of order of the respective Hubble scale. They are, however, completely washed out by baryon and photon diffusion at the later stages of the universe's evolution.
Interactions of heavy Majorana neutrinos in the thermal phase of the early universe may be the origin of the cosmological matter-antimatter asymmetry. This mechanism of baryogenesis implies stringent constraints on light and heavy Majorana neutrino masses. We derive an improved upper bound on the CP asymmetry in heavy neutrino decays which, together with the kinetic equations, yields an upper bound on all light neutrino masses of 0.1 eV. Lepton number changing processes at temperatures above the temperature T_B of baryogenesis can erase other, pre-existing contributions to the baryon asymmetry…
Interactions of heavy Majorana neutrinos in the thermal phase of the early universe may be the origin of the cosmological matter-antimatter asymmetry. Successful baryogenesis, independent of initial conditions, is possible for neutrino masses in the range $10^{-3} {eV} \leq m_i \lesssim 0.1$ eV. Remarkably, this mass window is consistent with the evidence for neutrino masses from oscillations.
In some baryogenesis scenarios, the universe acquires a non-vanishing average baryonic charge, but the baryon to photon ratio is not spatially constant and can be even negative in some space regions. This allows for existence of lumps of antimatter in our neighborhood and the possibility that very compact antimatter objects make a part of cosmological dark matter. Here I discuss the peculiar signatures which may be observed in a near future.
We study the implications of thermal leptogenesis for neutrino parameters. Assuming that decays of N_1, the lightest of the heavy Majorana neutrinos, initiate baryogenesis, we show that the final baryon asymmetry is determined by only four parameters: the CP asymmetry epsilon_1, the heavy neutrino mass M_1, the effective light neutrino mass \tilde{m}_1, and the quadratic mean \bar{m} of the light neutrino masses. Imposing the CMB measurement of the baryon asymmetry as constraint on the neutrino parameters, we show, in a model independent way, that quasi-degenerate neutrinos are incompatible wi…
There exists a class of cosmic strings that turn matter into antimatter (Alice strings). In a GUT where the unbroken gauge group contains charge conjugation ($C$), such strings form when a phase transition renders $C$ a discrete symmetry. They become boundaries of domain walls at a later, $C$-breaking transition. These `Alice walls' are cosmologically harmless, but can play an important role in baryogenesis. We present a three-generation toy model with scalar baryons, where a quasi-static Alice wall (or a gas of such walls) temporarily gives rise to net baryogenesis of uniform sign everywhere …
A simple TeV scale model for baryon and lepton number violation is presented, where neutrino mass arises via a one-loop radiative seesaw effect and B-violation obeys $ΔB=2$ selection rule. The stability of proton is connected to the neutrino mass generation. Matter-antimatter asymmetry is generated in this model via resonant baryogenesis mechanism.
A possible existence of cosmologically large domains of antimatter or astronomical ``anti-objects'' is discussed. A brief review of different scenarios of baryogenesis predicting a noticeable amount of antimatter is given. Though both theory and observations indicate that the universe is most possibly uniformly charge asymmetric without any noticeable amount of antimatter, several natural scenarios are possible that allow for cosmologically (astronomically) interesting objects in close vicinity to us. The latter may be discovered by observation of cosmic ray antinuclei.
We explore the possibility of baryogenesis without departure from thermal equilibrium. A possible scenario is found, though it contains strong constraints on the size of the $CPT$ violation ($CPTV$) effects and on the role of the $B$ (baryon number) nonconserving interactions which are needed for it.
The origin of the matter-antimatter asymmetry remains one of the most fundamental problems of cosmology. In this talk I present a novel scenario for baryogenesis at the electroweak scale, without the need for a first order phase transition. It is based on the out of equilibrium resonant production of long wavelength Higgs and gauge configurations, at the end of a period of inflation, which induces a large rate of sphaleron transitions, before thermalization at a temperature below critical.
The classical picture of GUT baryogenesis has been strongly modified by theoretical progress concerning two nonperturbative features of the standard model: the phase diagram of the electroweak theory, and baryon and lepton number changing sphaleron processes in the high-temperature symmetric phase of the standard model. We briefly review three viable models, electroweak baryogenesis, the Affleck-Dine mechanism and leptogenesis and discuss the prospects to falsify them. All models are closely tied to the nature of dark matter, especially in supersymmetric theories. In the near future results fr…
In the presence of background fields that spontaneously violate Lorentz invariance, a matter-antimatter asymmetry can be generated even in thermal equilibrium. In this paper we systematically investigate models of this type, showing that either high-energy or electroweak versions of baryogenesis are possible, depending on the dynamics of the Lorentz-violating fields. We identify two scenarios of interest: baryogenesis from a weak-scale pseudo-Nambu-Goldstone boson with intermediate-scale baryon-number violation, and sphaleron-induced baryogenesis driven by a constant-magnitude vector with a la…
We argue that inflationary dynamics may support a scenario where significant matter-antimatter asymmetry is generated from initially small-scale quantum fluctuations that are subsequently stretched out over large scales. This scenario can be realised in extensions of the Standard Model with an extra gauge symmetry having mixed anomalies with the electroweak gauge symmetry. Inflationary baryogenesis in a model with gauged baryon number is considered in detail.
We revisit the production of baryon asymmetries in the minimal type I seesaw model with heavy Majorana singlets in the GeV range. We include "washout" effects from scattering processes with gauge bosons, higgs decays and inverse decays, besides the dominant top scatterings. We show that in the minimal model with two singlets, and for an inverted light neutrino ordering, future measurements from SHiP and neutrinoless double beta decay could in principle provide sufficient information to predict the matter-antimatter asymmetry in the universe.
We propose a new mechanism for explaining the observed asymmetry between matter and antimatter, based on nonperturbative physics at the QCD scale. Our mechanism is a charge separation scenario, making use of domain walls separating the recently discovered long-lived metastable vacua from the lowest energy vacuum. The walls acquire a fractional negative baryon charge, leaving behind a compensating positive baryon charge in the bulk. The regions of metastable vacuum bounded by walls ("B-shells") will contribute to the dark matter of the Universe.
In the defect-mediated electroweak baryogenesis scenario, baryons are produced in well separated regions of space. It is shown that between the electroweak phase transition at a temperature of $T \sim 100 {\rm GeV}$ and the end of nucleosynthesis at $T \sim 1 {\rm KeV}$ the baryon inhomogeneities dissipate, and that no constraints on defect-mediated electroweak baryogenesis can be derived from considerations of inhomogeneous nucleosynthesis.
The paper suggests a left-right mirror symmetric model to account for the baryogenesis and asymmetric dark matter. The model can simultaneously accommodate the standard model, neutrino physics, matter-antimatter asymmetry and dark matter. In particular, it naturally and elegantly explains the origin of the baryon and dark matter asymmetries, and clearly gives the close interrelations of them. In addition, the model predicts a number of interesting results, e.g. the cold dark matter neutrino mass is $3.1$ times the proton mass. It is also feasible and promising to test the model in future exper…
We present detailed numerical calculations of the light element abundances synthesized in a Universe consisting of matter- and antimatter- domains, as predicted to arise in some electroweak baryogenesis scenarios. In our simulations all relevant physical effects, such as baryon-antibaryon annihilations, production of secondary particles during annihilations, baryon diffusion, and hydrodynamic processes are coupled to the nuclear reaction network. We identify two dominant effects, according to the typical spatial dimensions of the domains. Small antimatter domains are dissipated via neutron dif…
Several independent observations of the Galactic core suggest hitherto unexplained sources of energy. We suggest that dark matter in the form of dense antimatter nuggets could provide a natural site for electron and proton annihilation, providing 511 keV photons, gamma-rays, and diffuse keV x-ray radiation. We show that identifying dark matter as antimatter nuggets is consistent with the observed emissions, and we make definite predictions about their spectrum and morphology. If correct, our proposal not only identifies dark matter and explains baryogenesis, but allows x-ray observations to di…
We review observational evidence for a matter-antimatter asymmetry in the early universe, which leads to the remnant matter density we observe today. We also discuss observational bounds on the presence of antimatter in the present day universe, including the possibility of a large lepton asymmetry in the cosmic neutrino background. We briefly review the theoretical framework within which baryogenesis, the dynamical generation of a matter-antimatter asymmetry, can occur. As an example, we discuss a testable minimal model that simultaneously explains the baryon asymmetry of the universe, neutri…
We study a mechanism through which the cosmic dark matter density can be explained simultaneously with the observed baryon asymmetry of the Universe. At the core of our proposal lie the out-of-equilibrium scattering processes of bath particles which are responsible for the production of feebly-interacting dark matter. The same processes violate $CP$, which further leads to an asymmetry between matter and antimatter being generated in the visible sector. We focus on the possibility that these interactions are described through non-renormalizable operators, which leads to both dark matter and th…
In order to address the baryon asymmetry in the Universe one needs to understand the origin of baryon (B) and lepton (L) number violation. In this article, we discuss the mechanism of baryogenesis via leptogenesis to explain the matter-antimatter asymmetry in theories with spontaneous breaking of baryon and lepton number. In this context, a lepton asymmetry is generated through the out-of-equilibrium decays of right-handed neutrinos at the high-scale, while local baryon number must be broken below the multi-TeV scale to satisfy the cosmological bounds on the dark matter relic density. We demon…
In a non-minimal Higgs framework, we present a novel mechanism in which the CP violating dark particles only interact with the SM through the gauge bosons, primarily the $Z$ boson. Such $Z$-portal dark CP violation is realised in the regions of the parameter space where Higgs-mediated (co)annihilation processes are sub-dominant and have negligible contributions to the DM relic density. We show that such $Z$-portal CP violating DM can still thermalise and satisfy all experimental and observational bounds and discuss implications of such phenomena for electroweak baryogenesis.
The cosmological baryon asymmetry can be explained as remnant of heavy Majorana neutrino decays in the early universe. We study this mechanism for two models of neutrino masses with a large ν_μ-ν_τmixing angle which are based on the symmetries SU(5) x U(1)_F and SU(3)_c x SU(3)_L x SU(3)_R x U(1)_F, respectively. In both cases B-L is broken at the unification scale Λ_{GUT}. The models make different predictions for the baryogenesis temperature and the gravitino abundance.
R-parity and baryon number violating operators can be allowed in the Supersymmetric Standard Model and thus lead to interesting baryon number violating processes such as neutron-antineutron oscillations and baryogenesis of the Universe via the decay of the lightest supersymmetric particle (LSP). Adopting the LSP baryogenesis mechanism realized by the late decay of the axino, we identify a single coupling lambda''_313 as a common origin for the matter-antimatter asymmetry of the Universe as well as potentially observable neutron-antineutron oscillation rates. From this, rather strong constraint…
The cosmological matter-antimatter asymmetry can arise from the baryon number conserving CP asymmetry in two body decays of heavy particles, when the two final states carry equal and opposite baryon number, and one couples directly or indirectly to electroweak sphalerons so that its baryon asymmetry gets partly reprocessed into a lepton asymmetry, while the other remains chemically decoupled from the thermal bath with its baryon content frozen. After sphaleron switchoff the decay of the decoupled particles inject in the thermal plasma an unbalanced baryon asymmetry, giving rise to baryogenesis…
Mechanisms for the generation of the matter-antimatter asymmetry and dark matter strongly depend on the reheating temperature T_R, the maximal temperature reached in the early universe. Forthcoming results from the LHC, low energy experiments, astrophysical observations and the Planck satellite will significantly constrain baryogenesis and the nature of dark matter, and thereby provide valuable information about the very early hot universe. At present, a wide range of reheating temperatures is still consistent with observations. We illustrate possible origins of matter and dark matter with fou…
The oscillation of the neutron $n$ into mirror neutron $n'$, its partner from dark mirror sector, can gradually transform an ordinary neutron star into a mixed star consisting in part of mirror dark matter. The implications of the reverse process taking place in the mirror neutron stars depend on the sign of baryon asymmetry in mirror sector. Namely, if it is negative, as predicted by certain baryogenesis scenarios, then $\bar{n}'-\bar{n}$ transitions create a core of our antimatter gravitationally trapped in the mirror star interior. The annihilation of accreted gas on such antimatter cores c…
In four-space-time dimensional string/brane theory, obtained either through compactification of the extra spatial dimensions, or by appropriate restriction to brane worlds with three large spatial dimensions, the rich physics potential associated with the presence of non-trivial Kalb-Ramond (KR) axion-like fields has not been fully exploited so far. In this talk, I discuss a scenario whereby such fields produce spontaneous Lorentz- and CPT-violating cosmological backgrounds over which strings propagate, which in the early Universe can lead to Baryogenesis through Leptogenesis in models with he…
The generation of a matter-antimatter asymmetry in the Universe may be induced by the propagation of fermions in non-trivial, spherically asymmetric (and hence Lorentz violating) gravitational backgrounds. Such backgrounds may characterise the epoch of the early universe. The key point in these models is that the background induces different dispersion relations, hence populations, between fermions and antifermions, and thus CPT Violation (CPTV) appears in thermal equilibrium. Species populations may freeze out leading to leptogenesis and baryogenesis. We consider here a string-inspired scenar…
We investigate the electroweak phase transition patterns for a recently proposed baryogenesis model with CP violation originated in the dark sector. The model includes a complex scalar singlet-Higgs boson portal, a $U(1)_l$ gauge lepton symmetry with a $Z^\prime$ gauge boson portal and a fermionic dark matter particle. We find a novel thermal history of the scalar sector, featuring a $Z_2$ breaking singlet vacuum in the early Universe driven by a dark Yukawa coupling, that induces a one-step strongly first order electroweak phase transition. We explore the parameter space that generates the ob…
We study the generation of the matter-antimatter asymmetry during bosonic preheating, focusing on the sources of the asymmetry. If the asymmetry appears in the multiplication factor of the resonant particle production, the matter-antimatter ratio will grow during preheating. On the other hand, if the asymmetry does not grow during preheating, one has to find out another reason. We consider several scenarios for the asymmetric preheating to distinguish the sources of the asymmetry. We also discuss a new baryogenesis scenario, in which the asymmetry is generated without introducing neither loop …
In this work, we propose an economical model to address some open cosmological problems such as the absence of the initial cosmological singularity, an early acceleration of the Universe and the generation of matter-antimatter asymmetry. The model is based on a scenario in which the early Universe consists of a non-linear electrodynamics fields. It is found that the non-linear electrodynamics model has an equation of state $p=\frac{1}{3} ρ- \frac{4}{3} βρ^{1+α}$ which shows that the Universe undergoes an early epoch acceleration to a radiation era given by $p =\frac{1}{3} ρ$. We show that the …
The strong CP-violating parameter is small today as indicated by constraints on the neutron electric dipole moment. In the early universe, the QCD axion has not yet relaxed to its QCD-cancelling minimum and it is natural to wonder whether this large CP violation could be responsible for baryogenesis. We show that strong CP violation from the QCD axion can be responsible for the matter antimatter asymmetry of the universe in the context of cold electroweak (EW) baryogenesis if the EW phase transition is delayed below the GeV scale. This can occur naturally if the Higgs couples to a O(100) GeV d…
K-essence is a possible candidate for dark energy of the Universe. In this paper we consider couplings of k-essence to the matter fields of the standard electroweak theory and study the effects of the cosmological CPT violation induced by the CPT violating {\bf Ether} during the evolution of the k-essence scalar field on the laboratory experiments and baryogenesis. Our results show that the matter and antimatter asymmetry can be naturally explained {\it via} leptogenesis without conflicting with the experimental limits on CPT violation test. The mechanism for baryogenesis proposed in this pape…
We present a simple mechanism which allows the simultaneous generation of the baryon asymmetry of the Universe along with its dark matter content. To this goal, we employ the out-of-equilibrium decays of heavy bath states into a feebly coupled dark matter particle and Standard Model charged fermions. These decays lead to dark matter production via the freeze-in mechanism and, assuming that they further violate $CP$, can generate a viable matter-antimatter asymmetry in the resonant regime. We illustrate this mechanism by studying a particular realization of this general scenario, where the role…
We show that an inhomogeneous cosmological lepton number may have produced turbulence in the primordial plasma when neutrinos entered (almost) free-streaming regime. This effect may be responsible for the origin of cosmic magnetic fields and give rise to a detectable background of gravitational waves. An existence of inhomogeneous lepton asymmetry could be naturally generated by active-sterile neutrino oscillations or by some versions of Affleck and Dine baryogenesis scenario.
The origin of the matter-antimatter asymmetry of the universe remains one of the outstanding questions yet to be answered by modern cosmology and also one of only a handful of problems where the need of a larger number of degrees of freedom than those contained in the standard model (SM) is better illustrated. An appealing scenario for the generation of baryon number is the electroweak phase transition that took place when the temperature of the universe was about 100 GeV. Though in the minimal version of the SM, and without considering the interaction of the SM particles with additional degre…
We review scenarios of baryogenesis through leptogenesis at early epochs of the universe, in string-inspired minimal extensions of the Standard Model (SM), involving heavy right-handed Majorana neutrinos. Spontaneous violation of CPT symmetry is induced by appropriate (in general, temperature-dependent) backgrounds of the Kalb-Ramond (KR) axion field, which has its origins in the (bosonic) massless string multiplet. As interesting features of the model, we also discuss two issues associated with quantum (chiral) anomalies: (i) the non-contribution of the KR axion background to the (anomalous) …
