Spontaneous Baryogenesis Research Articles

Equation of motion of a classical scalar field with back reaction of produced particles

In the one-loop approximation we derive the equation of motion for a classical scalar field ϕ c ( t) with the back reaction of particle production included. Renormalization of mass and couplings of ϕ c is done explicitly. The equation is non-local in time, but can easily be treated perturbatively or numerically. For the weak trilinear coupling of the external field to the produced particles, the new equation gives the same solution as the familiar one with the Γ ϕ ̇ c term. For a stronger coupling and other types of couplings the results are significantly different. The equation can be applied to the universe heating by the inflaton decay and to spontaneous baryogenesis.

Baryogenesis, 30 years after

A review of the basic principles of baryogenesis is given. Baryogenesis in heavy particle decays as well as electroweak, SUSY-condensate, and spontaneous baryogenesis are discussed. The models of abundant creation of antimatter in the universe are briefly reviewed.

Baryogenesis during reheating in natural inflation and comments on spontaneous baryogenesis

We calculate the baryon asymmetry created by the decay of a pseudo Nambu-Goldstone boson whose interactions violate baryon number conservation. Our results are in disagreement with previous results in the original spontaneous baryogenesis models for the asymmetry produced by the decay of an oscillating scalar field with B number violating derivative couplings; we find that the net baryon number density is proportional to $\th_i^3$, where $\th_i$ is the amplitude of the PNGB-field in natural inflation at the onset of reheating. We also discuss our disagreement with the interpretation of $\dot\theta$ as an effective chemical potential for baryon number in spontaneous baryogenesis models. While our calculation of the asymmetry is carried out in the context of natural inflation our approach is generally valid for baryogenesis models using decaying classical fields. In the Appendices, we include a complete derivation of the number density of particles produced by the decay of a classical scalar field; this number density is proportional to the integral over momenta of the one pair production amplitude.

CP violation for electroweak baryogenesis from mixing of standard model and heavy vector quarks.

It is known that the CP violation in the minimal standard model is insufficient to explain the observed baryon asymmetry of the Universe in the context electroweak baryogenesis. In this paper we consider the possibility that the additional CP violation required could originate in the mixing of the standard model quarks and heavy vector quark pairs. We consider the baryon asymmetry in the context of the spontaneous baryogenesis scenario. It is shown that, in general, the CP-violating phase entering the mass matrix of the standard model and heavy vector quarks must be space dependent in order to produce a baryon asymmetry, suggesting that the additional CP violation must be spontaneous in nature. This is true for the case of the simplest models which mix the standard model and heavy vector quarks. We derive a charge potential term for the model by diagonalizing the quark mass matrix in the presence of the electroweak bubble wall, which turns out to be quite different from the fermionic hypercharge potentials usually considered in spontaneous baryogenesis models, and obtain the rate of baryon number generation within the wall. We find, for the particular example where the standard model quarks mix with weak-isodoublet heavy vector quarks via the expectation value of a gauge singlet scalar, that we can account for the observed baryon asymmetry with conservative estimates for the uncertain parameters of electroweak baryogenesis, provided that the heavy vector quarks are not heavier than a few hundred GeV and that the coupling of the standard model quarks to the heavy vector quarks and gauge singlet scalars is not much smaller than order of 1, corresponding to a mixing angle of the heavy vector quarks and standard model quarks not much smaller than order of ${10}^{\mathrm{\ensuremath{-}}1}$. \textcopyright{} 1996 The American Physical Society.

Linear response theory approach to spontaneous baryogenesis

We reconsidered the spontaneous baryogenesis mechanism by Cohen, Kaplan and Nelson. Using linear response theory, we calculate the modifications on the thermal averages of the charges of the system due to the presence of a space time dependent “charge potential” l'or a quantum number not orthogonal to baryon number. The local equilibrium configuration is discussed, showing that, as a consequence of non zero densities for conserved charges, the B + L density is driven to non zero values by sphaleronic processes. Solving a rate equation for the baryon number generation, we obtain an expression for the final baryon asymmetry of the Universe containing the relevant parameters of the bubble wall, i.e. its velocity, its width, and the width of the region in which sphalerons are active. Compared to previous estimates in which transport effects were not taken into account, we tind an enhancement of nearly three orders of magnitude in the baryon asymmetry. Finally, the role of QCD sphalerons in cooperation with transport effects is analyzed, showing that the net result depends crucially on the particle species which enter into the charge potential.

Particle currents on a CP violating Higgs background and the spontaneous baryogenesis mechanism

We compute the particle currents induced on a bubble wall background at finite temperature in a model with CP violation in the Higgs sector. Using a field theory approach we show that fermionic currents arise at one loop, so that a suppression factor O( h tΦ πT ) 2 with respect to previous computations is found. The contributions to the Higgs currents are also derived and their relevancy for the spontaneous baryogenesis mechanism is discussed.

A simple estimate of the effect of diffusion on the baryon number generated in spontaneous baryogenesis models

Recently it has been observed that the transport of conserved charges into the electroweak bubble wall alters the spontaneous baryogenesis scenario, by allowing the baryon asymmetry to be generated over a larger volume including the outside of the bubble. We give here a very simple analytic estimate of the change in the baryon number generated, by considering a simple toy model with a single particle and a single conserved charge. Our results indicate that in general diffusion itself will produce at most a small enhancement of the baryon asymmetry as compared with the original spontaneous baryogenesis scenario; by no more than a factor of order 10. This suggests that any large enhancement of the baryon asymmetry due to diffusion effects in realistic multi-particle models can only be due to the elimination of cancellations between the contributions of the individual particles. Our discussion should be generally useful for making simple estimates of the baryon number generated including diffusion effects, given the asymmetry generated in the original spontaneous baryogenesis model.

Diffusion enhances spontaneous electroweak baryogenesis

We include the effects of diffusion in the electroweak spontaneous baryogenesis scenario and show that it can greatly enhance the resultant baryon density, by as much as a factor of 1/α w 4 ∼ 10 6 over previous estimates. Furthermore, the baryon density produced is rather insensitive to parameters characterizing the first order weak phase transition, such as the width and propagation velocity of the phase boundary.

Spontaneous baryogenesis with observable CP violation.

Using a left-right symmetric model with Spontaneous CP Violation and the hypothesis of a weakly first order electroweak phase transition we derive a relation between the produced baryon asymmetry and the observed parameter $\varepsilon$, describing CP violation in the $K$ system.

Strong sphalerons and electroweak baryogenesis

We analyze the spontaneous baryogenesis and charge transform mechanisms suggested by Cohen, Kaplan and Nelson for baryon asymmetry generation in extended versions of electroweak theory. We find that accounting for non-perturbative chirality-breaking transitions due to strong sphalerons reduces the baryonic asymmetry by the factor ( m t πT ) 2 or α W , provided those processes are in thermal equilibrium.

Spontaneous baryogenesis in supersymmetric models

In this paper we extend the results of previous work on spontaneous baryogenesis to general models involving CP violation in the Higgs sector. We show how to deal with anomalous terms appearing in the effective potential arising from phase changes in the vacuum expectation values of the Higgs fields. In particular, this enables us to apply this mechanism to general supersymmetric models including the minimal supersymmetric standard model, and the extended model with a gauge singlet. A comparison is made between this approach, and that in which one solves the equations of motion for Higgs winding modes. As anticipated in earlier work, the effect of the latter approach is found to be small.

Spontaneous baryogenesis at the weak phase transition

We discuss baryogenesis during the weak phase transition in models with CP violation in the scalar potential. If the transition is first order, classical evolution of the scalar fields can split particle-antiparticle energy levels. A net baryon number will then be produced by anomalous weak baryon number violation. We can explain the observed value ϱ B S ≅10 −10 .

On the primordial origin of isocurvature perturbations

We analyse the different models proposed in the literature for the origin of the initial conditions needed in the phenomenological isocurvature model. We find that the model with an additional weakly interacting scalar field present during inflation besides the inflation which decays into radiation after baryogenesis do not provide these isocurvature initial conditions. Instead, the case in which the additional scalar field remains as a dark matter component up to the present epoch, the axions and the spontaneous baryogenesis model are possible candidates to originate them.

Isocurvature baryon number fluctuations in an inflationary universe

In conventional scenarios of baryogenesis it is extremely difficult, if not impossible, to produce local fluctuations in the baryon-to-photon ratio (so-called isocurvature baryon number fluctuations) on sufficiently large scales to be important for structure formation. Using a recently proposed scenario for baryogenesis called “spontaneous baryogenesis”, we show that isocurvature baryon number fluctuations with the Zel'dovich spectrum and amplitude ∼ 10 −3 can be produced in inflationary universe models. It is also possible that non-scale invariant baryon number fluctuations could be produced in more complicated inflationary scenarios, and if so might help to revive the baryon-dominated, or neutrino-dominated scenarios of structure formation.

Spontaneous baryogenesis

The recently discovered mechanism of “spontaneous baryogenesis” for generating the baryon asymmetry is implemented in several particle physics models. In these scenarios, baryon number is an approximate symmetry spontaneously broken at a scale |;. The baryon asymmetry is generated without CP violation. Furthermore, this can come about during an epoch when baryon violation is in thermal equilibrium. We consider how various observational constraints affect the realization of this mechanism in acceptable models of particle interactions, and find that the observed baryon asymmetry can be produced for |;≳ 3 × 10 13 GeV.