Many models of baryogenesis rely on anomalous particle physics processes to give baryon number violation. By numerically evolving the electroweak equations on a lattice, we show that baryogenesis in these models creates helical cosmic magnetic fields. After a transitory period, electroweak dynamics is found to conserve the Chern-Simons number and the total electromagnetic helicity. We argue that baryogenesis could lead to magnetic fields of nano-Gauss strength today on astrophysical length scales. In addition to being astrophysically relevant, such helical magnetic fields can provide an independent probe of baryogenesis and CP violation in particle physics.
We propose a new alternative for baryogenesis which resolves a number of the problems associated with GUT and electroweak scenarios, and which may allow baryogenesis even in modest extensions of the standard model. If the universe never reheats above the electroweak scale following inflation, GUT baryon production does not occur and at the same time thermal sphalerons, gravitinos and monopoles are not produced in abundance. Nevertheless, non-thermal production of sphaleron configurations via preheating could generate the observed baryon asymmetry of the universe.
We study a new scenario for baryogenesis due to the spontaneous breaking of the $CPT$ invariance through the interaction between a baryon current and a hypermagnetic helicity. The hypermagnetic helicity (Chern-Simons number) of $U(1)_Y$ provides a $CPT$ violation background for the generation of baryons via sphaleron processes, which protects these baryons from the sphaleron wash-out effect in thermal equilibrium. It is shown that if the present amplitude of the resultant magnetic fields are sufficiently large, for a wide range mass scale (from TeV to the Planck scale), the observational magni…
We consider the scenario of electroweak baryogenesis mediated by cosmological defects in a model of extra dimension. We consider the domain wall on the brane in higher-dimensional theories.The electroweak breaking scale is suppressed and the sphaleron interaction is activated in the false vacuum.
The cosmological baryon asymmetry is closely related to neutrino properties due to the non-perturbative sphaleron processes in the high-temperature symmetric phase of the standard model. We review some aspects of this connection with emphasis on cosmological bounds on neutrino masses, leptogenesis and possible implications for dark matter.
We reanalyse the sphaleron bound of electroweak baryogenesis when allowing deviations to the Friedmann equation. These modifications are well motivated in the context of brane cosmology where they appear without being in conflict with major experimental constraints on four-dimensional gravity. While suppressed at the time of nucleosynthesis, these corrections can dominate at the time of the electroweak phase transition and in certain cases provide the amount of expansion needed to freeze out the baryon asymmetry without requiring a strongly first order phase transition. The sphaleron bound is …
We consider the scenario of electroweak baryogenesis mediated by cosmological defect in models of supersymmetry breaking. When the effective electroweak breaking scale is raised in the defect configuration, the mechanism of electroweak baryogenesis works at a higher energy scale. The baryon charge produced by the mechanism is captured in the defect, protected from sphalerons and then released when the defect decay.
The standard requirement for the production of baryons at the electroweak phase transition, that the phase transition be first order and the sphaleron bound be satisfied, is predicated on the assumption of a radiation dominated universe at that epoch. One simple alternative - domination by the energy in a kinetic mode of a scalar field which scales as $1/a^6$ - gives a significantly weakened sphaleron bound for the preservation of a baryon asymmetry produced at a first-order phase transition, and allows the possibility that the observed baryon asymmetry be produced when the phase transition is…
The usual sphaleron bound and the statement of the impossibility of baryon production at a second order phase transition or analytic cross-over are reformulated in the first part of the paper as requirements of the expansion rate of the Universe at the electroweak scale. With an (exact or effective) additional contribution to the energy density scaling as 1/a^6, which dominates until just before nucleosynthesis, the observed baryon asymmetry may be produced at the electroweak scale in simple extensions of the Minimal Standard Model, even in the case that the phase transition is not first order…
We present a new scenario for the baryon number violation that may take place in models with large extra dimensions. Our idea is interesting because leptogenesis with a low reheating temperature requires an alternative source of the B+L violation to convert the produced leptons into baryons. If one considers a model with an intermediate compactification radius, the reheating temperature may be allowed to become higher than the critical temperature of the conventional electroweak phase transition. Our mechanism is still important in this case, because it provides the phase boundary, which is an…
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…
We propose a new variant of the Affleck-Dine baryogenesis mechanism in which a rolling scalar field couples directly to left- and right-handed neutrinos, generating a Dirac mass term through neutrino Yukawa interactions. In this setup, there are no explicitly CP violating couplings in the Lagrangian. The rolling scalar field is also taken to be uncharged under the $B - L$ quantum numbers. During the phase of rolling, scalar field decays generate a non-vanishing number density of left-handed neutrinos, which then induce a net baryon number density via electroweak sphaleron transitions.
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…
A generic prediction of models where supersymmetry is broken at scales within a few orders of magnitude of the weak scale and is fed down to the observable sector by gauge interactions is the existence of superconducting cosmic strings which carry baryon number. In this paper we propose a novel mechanism for the generation of the baryon asymmetry which takes place at temperatures much lower than the weak scale. Superconducting strings act like ``bags'' containing the baryon charge and protect it from sphaleron wash-out throughout the evolution of the Universe, until baryon number violating pro…
Radiation domination at the electroweak epoch is a simplifying assumption, but one for which there is no observational basis. Treating the expansion rate as a variable, I re-examine electroweak baryogenesis in various scenarios. At a first order phase transition the main effect is on the sphaleron bound, which becomes a lower bound on the expansion rate in any given theory. At a second-order or cross-over phase transition, the created baryon asymmetry is directly proportional to the expansion rate. I sketch an alternative post-inflationary cosmology, in which the kinetic energy of a scalar fie…
We propose a new mechanism of leptogenesis in which the asymmetries in lepton numbers are produced through the CP-violating oscillations of ``sterile'' (electroweak singlet) neutrinos. The asymmetry is communicated from singlet neutrinos to ordinary leptons through their Yukawa couplings. The lepton asymmetry is then reprocessed into baryon asymmetry by electroweak sphalerons. We show that the observed value of baryon asymmetry can be generated in this way, and the masses of ordinary neutrinos induced by the seesaw mechanism are in the astrophysically and cosmologically interesting range. Exce…
In the context of inflationary cosmology, we discuss a minimal baryogenesis scenario in which the resulting baryon to entropy ratio is determined by the amplitude of the anisotropies of the cosmic microwave background. The model involves a new $SU(2)_L$ scalar field which generates a Dirac neutrino mass and which is excited by quantum fluctuations during inflation, yielding a CP-violating phase. During the scalar field decay after inflation, an asymmetry in the left-handed neutrino number is generated, which then converts to a net baryon asymmetry via sphalerons. A lower limit on the expected …
We present a novel scenario for baryogenesis in a hybrid inflation model at the electroweak scale, in which the Standard Model Higgs field triggers the end of inflation. One of the conditions for successful baryogenesis, the departure from thermal equilibrium, is naturally achieved at the stage of preheating after inflation. The inflaton oscillations induce large occupation numbers for long-wavelength configurations of Higgs and gauge fields, which leads to a large rate of sphaleron transitions. We estimate this rate during the first stages of reheating and evaluate the amount of baryons produ…
We discuss the possibility of generating the baryon asymmetry of the Universe when the temperature of the Universe is much below the electroweak scale. In our model the evaporation of primordial black holes or the decay of massive particles re-heats the surrounding plasma to temperatures above the electroweak transition temperature leading to the restoration of electroweak symmetry locally. The symmetry is broken again spontaneously as the plasma cools and a baryon asymmetry is generated during the phase transition. This mechanism generates sufficient asymmetry for a second order electroweak p…
In this study we examine post-inflationary cosmologies dominated by a scalar field with the equation of state: p_phi=w_phi rho_phi (0 leq w_phi leq 1) in order to facilitate baryogenesis at the electroweak scale. We take a more conventional approach from one in Ref. 1 [Joyce, Prokopec] and assume that the Universe reheats by the scalar field decay before the nucleosynthesis epoch, and find a larger expansion rate at the electroweak scale than the one obtained in Ref. 1. The decaying field models suffer however from an entropy release that dilutes the baryon number produced at the electroweak s…
We investigate `non-local' schemes for baryogenesis at a first order electroweak phase transition, in which the effects of a $CP$ violating condensate on the bubble wall propagate into the unbroken phase where the sphaleron rate is unsupressed. Such a condensate exists in multi-Higgs extensions of the standard model, and may exist due to an instability in the minimal standard model. In this paper we first discuss the general problem of determining the $CP$ violating perturbations, distinguishing two regimes (quantum and classical). We then give an analytic treatment of quantum mechanical refle…
We describe a new mechanism for the generation of the baryon asymmetry of the universe during a first order electroweak phase transition. The mechanism requires the existence of two (or more) baryon number carrying scalar fields with masses and CP violating mixing which vary with the Higgs field expectation value. This mechanism can be implemented using squarks in supersymmetric theories or using leptoquarks. Our central observation is that reflection of these scalars from a bubble wall can yield a significant net baryon number flux into the symmetric phase, balanced by a flux of opposite sign…
Incorporating a realistic model for accretion of ultra-relativistic particles by primordial blackholes (PBHs), we study the evolution of an Einstein-de Sitter universe consisting of PBHs embedded in a thermal bath from the epoch $\sim 10^{-33}$ sec to $\sim 5\times 10^{-9}$ sec. In this paper we use Barrow et al's ansatz to model blackhole evaporation in which the modified Hawking temperature goes to zero in the limit of the blackhole attaining a relic state with mass $\sim m_{pl}$. Both single mass PBH case as well as the case in which blackhole masses are distributed in the range $8\times 10…
