Narrow Results

We present aspects of a model which attempts to unify the creation of cold dark matter, a CP-violating baryon asymmetry, and also a small, residual vacuum energy density, in the early universe. The model contains a primary scalar (inflaton) field and a primary pseudoscalar field, which are initially related by a cosmological, chiral symmetry. The nonzero vacuum expectation value of the pseudoscalar field spontaneously breaks CP invariance.

Combining one established idea with two recent ones, it is pointed out for the first time that three of the outstanding problems of particle physics and cosmology, i.e. neutrino mass, dark matter, and baryogenesis, may have a simple common solution, arising from the interactions of a single term, with experimentally verifiable consequences.

It is shown that, in the context of split supersymmetry, a simple model with a single complex scalar field can produce chaotic inflation and generate the observed amount of baryon asymmetry via the Affleck-Dine mechanism. Combining with constraints from WMAP data, all parameters in the model can be determined to within a narrow range. Possible effects due to non-equilibrium dynamics in the Affleck-Dine mechanism of baryogenesis are also examined.

We have studied here electroweak symmetry breaking and baryogenesis from the viewpoint of topological mass generation through chiral anomaly. It is shown that the SU(2) gauge symmetry of the electroweak theory breaks in two stages. In the final stage we have Z-strings produced at the phase transition. We have also studied the problem of baryogenesis in this formalism and the ratio of the baryon–antibaryon is found to be in good agreement with the observed value.

A successful baryogenesis theory requires a baryon-minus-lepton number violation if it works before the electroweak phase transition. The leading dimension-6 baryon number violating interactions conserve baryon-minus-lepton number, which dissociated baryogenesis from baryon number violation. We show that in some models, in which the baryon-minus-lepton number is violated in the proton and neutron decays, the baryogenesis and the nucleon decay could have a common origin. We extend the canonical seesaw model with an isotriplet leptoquark scalar and two isotriplet Higgs scalars and allow the Higgs triplet to have a quartic coupling with three leptoquark triplets and a cubic coupling with two Higgs doublets. The decays of the Higgs triplets can thus generate a baryon-minus-lepton asymmetry. The tiny vacuum expectation values of the Higgs triplets can naturally induce a testable proton decay even if the leptoquark is around the TeV scale. The leptoquark associated with any flavor neutrinos can mediate a neutrinoless double beta decay.

It was recently proposed that weakly interacting massive particles (WIMP) may provide new ways of generating the observed baryon asymmetry in the early universe, as well as addressing the cosmic coincidence between dark matter (DM) and baryon abundances. This suggests a new possible connection between weak scale new particle physics and modern cosmology. This review summarizes the general ideas and simple model examples of the two recently proposed WIMP baryogenesis mechanisms: baryogenesis from WIMP DM annihilation during thermal freeze-out, and baryogenesis from metastable WIMP decay after thermal freeze-out. This review also discusses the interesting phenomenology of these models, in particular, the experimental signals that can be probed in the intensity frontier experiments and the large hadron collider (LHC) experiments.

Although the big bang should have produced equal amounts of matter and antimatter, there is evidence that the universe does not contain significant amounts of antimatter. The usual explanations for this matter–antimatter asymmetry involve finding causes for Sakharov’s three conditions to be satisfied. However, if the composite photon theory is correct, antimatter galaxies should appear to us as dark matter, neither emitting light (that we can detect) or reflecting ordinary light. Thus the presence of antimatter galaxies may be harder to detect than previously thought. The large clumps of dark matter that have been observed by weak gravitation lensing could be clusters of antimatter galaxies. “Dark photons,” that are hypothesized to cause self-interactions between dark matter particles, are identified as antiphotons in the composite photon theory. The possibility of a patchwork universe, that had been previously excluded, is also re-examined.

A simple model is constructed based on the gauge symmetry $\mathrm{\text{SU}}{(3)}_c\times \mathrm{\text{SU}}{(2)}_L\times \mathrm{\text{U}}{(1)}_Y\times \mathrm{\text{SU}}{(2)}_{\ell }$, with only the leptons transforming nontrivially under $\mathrm{\text{SU}}{(2)}_{\ell }$. The extended symmetry is broken down to the Standard Model gauge group at TeV-scale energies. We show that this model provides a mechanism for baryogenesis via leptogenesis in which the lepton number asymmetry is generated by $\mathrm{\text{SU}}{(2)}_{\ell }$ instantons. The theory also contains a dark matter candidate — the $\mathrm{\text{SU}}{(2)}_{\ell }$ partner of the right-handed neutrino.

A brief review is given of some recent works where baryogenesis and dark matter have a common origin within the U(1) extensions of the Standard Model (SM) and of the minimal supersymmetric Standard Model (MSSM). The models considered generate the desired baryon asymmetry and the dark matter to baryon ratio. In one model, all of the fundamental interactions do not violate lepton number, and the total $B-L$ in the Universe vanishes. In addition, one may also generate a normal hierarchy of neutrino masses and mixings in conformity with the current data. Specifically, one can accommodate ${𝜃}_{13}\sim 9^{\circ }$ consistent with the data from Daya Bay reactor neutrino experiment.

We propose a new mechanism for generating both luminous and dark matter during cosmic inflation. According to this mechanism, ordinary and dark matter carry common charge which is associated with an anomalous U(1)${}_X$ group. Anomaly terms source ${𝒞}{𝒫}$ and U(1)${}_X$ charge violating processes during inflation, producing corresponding nonzero Chern–Simons numbers which are subsequently reprocessed into baryon and dark matter densities. The general framework developed is then applied to two possible extensions of the Standard Model with anomalous gauged $B$ and $B-L$, each with an additional dark matter candidate. In each scenario, we consider the parameter choices that predict the correct dark matter to baryonic matter density ratio and baryon asymmetry. Interestingly, under these conditions, for the U(1)${}_{B-L}$ extension we obtain a prediction for the mass of the dark matter candidate which is independent of the other choice of parameters, when assuming an ${\eta }_B$ and ${\rho }_{\mathrm{\text{DM}}}/{\rho }_B$.

We study the f(R) theory of gravity in an anisotropic metric and its effect on the baryon number-to-entropy ratio. The mechanism of gravitational baryogenesis based on the CPT-violating gravitational interaction between derivative of the Ricci scalar curvature and the baryon-number current is investigated in the context of the f(R) gravity. The gravitational baryogenesis in the Bianchi type I (BI) Universe is examined. We survey the effect of anisotropy of the Universe on the baryon asymmetry from the point of view of the f(R) theories of gravity and its effect on $n_b/s$ for radiation dominant regime.

A new scenario of baryogenesis via the ratchet mechanism is proposed based on an analogy with the forced pendulum. The oscillation of the inflaton field during the reheating epoch after inflation plays the role of the driving force, while the phase $𝜃$ of a scalar baryon field (a complex scalar field with baryon number) plays the role of the angle of the pendulum. When the inflaton is coupled to the scalar baryon, the behavior of the phase $𝜃$ can be analogous to that of the angle of the forced pendulum. If the oscillation of the driving force is adjusted to the pendulum’s motion, a directed rotation of the pendulum is obtained with a nonvanishing value of $\dot{𝜃}$, which models successful baryogenesis since $\dot{𝜃}$ is proportional to the baryon number density. Similar ratchet models which lead to directed motion have been used in the study of molecular motors in biology. There, the driving force is supplied by chemical reactions, while in our scenario this role is played by the inflaton during the reheating epoch.

In this work, we intend to address the matter–antimatter asymmetry via the gravitational baryogenesis mechanism in the background of a quantum theory of gravity. We investigate this mechanism under the framework of Hořava–Lifshitz gravity. We will compute the baryon-to-entropy ratio in the chosen framework and investigate its physical viability against the observational bounds. We also conduct the above study for various sources of matter like scalar field and Chaplygin gas as specific examples. We speculate that quantum corrections from the background geometry will lead to interesting results.

We review a testable, the axion quark nugget (AQN) model outside of the standard WIMP paradigm. The model was originally invented to explain the observed similarity between the dark and the visible components, ${\mathrm{\Omega }}_{\mathrm{\text{DM}}}\approx {\mathrm{\Omega }}_{\mathrm{\text{visible}}}$, in a natural way as both types of matter are formed during the same QCD transition and proportional to the same dimensional fundamental parameter of the system, ${\mathrm{\Lambda }}_{\mathrm{\text{QCD}}}$. In this framework, the baryogenesis is actually a charge segregation (rather than charge generation) process which is operational due to the ${𝒞}{𝒫}$-odd axion field, while the global baryon number of the Universe remains zero. The nuggets and anti-nuggets are strongly interacting but macroscopically large objects with approximately nuclear density. We overview several specific recent applications of this framework. First, we discuss the “solar corona mystery” when the so-called nanoflares are identified with the AQN annihilation events in corona. Secondly, we review a proposal that the recently observed by the Telescope Array puzzling events is a result of the annihilation events of the AQNs under thunderstorm. Finally, we overview a broadband strategy which could lead to the discovery the AQN-induced axions representing the heart of the construction.

Where is the anti-matter in our universe? This is the most significant open problem of the modern era. This paper is devoted to the study of cosmological impact of gravitational baryogenesis and its generalized case driven by [Davoudiasl et al., Phys. Rev. Lett. 93, 201301 (2004)]. In this class of baryogenesis, the Ricci scalar $R$ is derivatively coupled to the baryon current $J_B$ as $({\partial }_{i}R)J_B^i$. We examine the imbalance of baryon and anti-baryon of the universe in the context of $f(T,\mathrm{\Theta })$ gravity, where $T$ and $\mathrm{\Theta }$ are the torsion scalar and the trace of the energy–momentum tensor, respectively. We assume two $f(T,\mathrm{\Theta })$ models in which the first one contains the sum of second-order torsion tensors and the trace of energy–momentum tensor while the second one is the product of these terms. For all cases, we find the ratio of baryon number to entropy by considering the power-law scale factor. Finally, we compare our results with the observational value of baryon-number-density-to-entropy ratio. The baryon-to-entropy ratio against the first model lies in the range $7.5_{-3.5}^{+3.5}\times 10^{-11}$ while for the second model it contains $1.5_{-1.45}^{+1.5}\times 10^{-10}$. For generalized case of gravitational baryogenesis, we also obtain results that are compatible with the observation limit.

We consider the presence of cosmic string induced density fluctuations in the universe at temperatures below the electroweak phase transition temperature. Resulting temperature fluctuations can restore the electroweak symmetry locally, depending on the amplitude of fluctuations and the background temperature. The symmetry will be spontaneously broken again in a given fluctuation region as the temperature drops there (for fluctuations with length scales smaller than the horizon), resulting in the production of baryon asymmetry. The time scale of the transition will be governed by the wavelength of fluctuation and, hence, can be much smaller than the Hubble time. This leads to strong enhancement in the production of baryon asymmetry for a second order electroweak phase transition as compared to the case when transition happens due to the cooling of the universe via expansion. For a two-Higgs extension of the Standard Model (with appropriate CP violation), we show that one can get the required baryon to entropy ratio if fluctuations propagate without getting significantly damped. If fluctuations are damped rapidly, then a volume factor suppresses the baryon production. Still, the short scale of the fluctuation leads to enhancement of the baryon to entropy ratio by at least 3–4 orders of magnitude compared to the conventional case of second order transition where the cooling happens due to expansion of the universe.

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.

The model of radiative neutrino mass with dark matter proposed by one of us is extended to include a real singlet scalar field. There are then two important new consequences. One is the realistic possibility of having the lightest neutral singlet fermion (instead of the lightest neutral component of the dark scalar doublet) as the dark matter of the universe. The other is a modification of the effective Higgs potential of the Standard Model, consistent with electroweak baryogenesis.

The conventional baryogenesis mechanism is based on the one Higgs doublet within the Standard Model, at the electroweak scale T ~ 100 GeV. In this model, the strong first-order phase transition due to the spontaneous symmetry breaking imposes the following condition on the mass of the Higgs field: m_H ≲ 40 GeV, which is contrary to the recently observed value m_H ≃ 126 GeV. In this paper, we propose a baryogenesis mechanism within a two-Higgs-doublet model in which the phase transition occurs in one stage. This model is consistent with the observed mass of the Higgs. We obtain the true vacuum bubble wall velocity and thickness in this model. Then, we use nonlocal baryogenesis mechanism in which the interaction of fermions with the boundary of the expanding bubbles leads to CP violation and sphaleron mediated baryogenesis.

Neutrinoless double beta decay, lepton number violating collider processes and the Baryon Asymmetry of the Universe (BAU) are intimately related. In particular, lepton number violating processes at low energies in combination with sphaleron transitions will typically erase any preexisting BAU. In this contribution, we briefly review the tight connection between neutrinoless double beta decay, lepton number violating processes at the LHC and constraints from successful baryogenesis. We argue that far-reaching conclusions can be drawn unless the baryon asymmetry is stabilized via some newly introduced mechanism.