Vacuum stability in the singlet Majoron model

We study the vacuum stability of the singlet Majoron model using full renormalization group improved scalar potential and Monte Carlo techniques. We show that in the perturbative regime of the various free parameters, the vacuum stability requirement together with LEP limits is passed by 18% of the parameter space if the scale of new physics is 10 TeV and 6% if the scale is $10^{14}$ GeV. Moreover, if the baryogenesis condition for scalar couplings is required, no portion of the parameter space survives.Comment: 9 pages + 1 uuencoded figur

Low Energy Leptogenesis in Left-Right Symmetric Models

We propose a new mechanism for baryogenesis. We study the effective potential of left-right extension of the standard model and show that there can be a first order phase transition at the left-right symmetry breaking and hence $(B-L)$ symmetry breaking scale, which is around TeV in our scenario. As a result, although $(B-L)$ violating interactions are in equilibrium at this scale, enough $(B-L)$ asymmetry may be generated. This $(B-L)$ asymmetry is then converted to baryon asymmetry during the anomalous electroweak process. If right handed gauge bosons are seen in the TeV scale, then we argue that this will be the only consistent mechanism to generate baryon asymmetry of the universe.Comment: 16 pages (Latex file) - 1 postscript figure appende

Electroweak Baryogenesis and Constraints on Left-handed Majorana Neutrino Masses

The lepton number violating interactions generated by the light Majorana neutrinos can erase the primordial baryon asymmetry of the universe during the electroweak phase transition. The Majorana masses of the left-handed neutrinos are constrained to avoid this problem. These constraints do not depend on the $(B-L)$ symmetry breaking mechanism.Comment: 10 pages, LATEX file with a postscript file attached at the end with instructions to prin

Protecting the Baryon Asymmetry with Thermal Masses

We consider the evolution of baryon number $B$ in the early universe under the influence of rapid sphaleron interactions and show that $B$ will remain nonzero at all times even in the case of $B-L = 0$. This result arises due to thermal Yukawa interactions that cause nonidentical dispersion relations (thermal masses) for different lepton families. We point out the relevance of our result to the Affleck-Dine type baryogenesis.Comment: 11pp., plain tex, UMN-TH-1248/94, CfPA-TH-94-1

Quantum Fluctuations around the Electroweak Sphaleron

We present an analysis of the quantum fluctuations around the electroweak sphaleron and calculate the associated determinant which gives the 1--loop correction to the sphaleron transition rate. The calculation differs in various technical aspects from a previous analysis by Carson et al. so that it can be considered as independent. The numerical results differ also -- by several orders of magnitude -- from those of this previous analysis; we find that the sphaleron transition rate is much less suppressed than found previously.Comment: DO-TH-93/19 39 pages, 5 figures (available on request as Postscript files or via Fax or mail), LaTeX, no macros neede

CP-Violation and Baryogenesis in The Low Energy Minimal Supersymmetric Standard Model

In the context of the minimal supersymmetric extension of the Standard Model the effect of a realistic wall profile is studied. It has been recently showed that in the presence of light stops the electroweak scale phase transition can be strong enough for baryogenesis. In the presence of non-trivial CP-violating phases of left-handed mixing terms and Higgsino mass, the largest $n_B/s$ is created when Higgsino and gaugino mass parameters are degenerate, $\mu = M_2$. In the present paper we show that realistic wall profiles suppress the generated baryon number of the universe, so that quite a stringent bound |\sin\phi_\mu | \gsim 0.2 for $\mu$-phase $\phi_\mu$ can be inferred.Comment: 8 pages(LaTex), 2 figure

A Chandra survey of fluorescence Fe lines in X-ray Binaries at high resolution

In this paper we present a comprehensive survey of 41 X-ray binaries (10 HMXBs and 31 LMXBs) with Chandra, with specific emphasis on the Fe K region and the narrow Fe Kalpha line, at the highest resolution possible. We find that: a) The Fe Kalpha line is always centered at 1.9387 +- 0.0016 Angstroms, compatible with Fe I up to Fe X; we detect no shifts to higher ionization states nor any difference between HMXBs and LMXBs. b) The line is very narrow, with FWHM < 5 mAngstroms, which means that the reprocessing material is not rotating at high speeds. c) Fe Kalpha fluorescence is present in all the HMXB in the survey while such emissions are very rare (~ 10% ) among LMXBs. d) The lack of Fe line emission is always accompanied by the lack of any detectable K edge. e) We obtain the empirical curve of growth of the equivalent width of the Fe Kalpha line versus the density column of the reprocessing material, i.e. EW_{Kalpha} vs N_{H}, and show that it is consistent with a reprocessing region spherically distributed around the compact object. f) We show that fluorescence in X-ray binaries follows the X-ray Baldwin effect. We interpret this finding as evidence of decreasing neutral Fe abundance with increasing X-ray illumination and use it to explain some spectral states of Cyg X-1 and as a possible cause of the lack of narrow Fe line emission in LMXBs. g) Finally, we study anomalous morphologies. We present the first evidence of a Compton shoulder in the HMXB X1908+075. Also the Fe Kalpha lines of 4U1700-37 and LMC X-4 present asymmetric wings suggesting the presence of highly structured stellar winds in these systems.Comment: 12 pages, 11 figures, accepted for publication in Ap

Structure of the Quark Propagator at High Temperature

In the high temperature, chirally invariant phase of QCD, the quark propagator is shown to have two sets of poles with different dispersion relations. A reflection property in momentum space relates all derivatives at zero-momentum of the particle and hole energies, the particle and hole damping rates, and the particle and hole residues. No use is made of perturbation theory.Comment: 8 pages, Latex twocolum

Models of Neutrino Masses and Baryogenesis

Majorana masses of the neutrino implies lepton number violation and is intimately related to the lepton asymmetry of the universe, which gets related to the baryon asymmetry of the universe in the presence of the sphalerons during the electroweak phase transition. Assuming that the baryon asymmetry of the universe is generated before the electroweak phase transition, it is possible to dicriminate different classes of models of neutrino masses. While see-saw mechanism and the triplet higgs mechanism are preferred, the Zee-type radiative models and the R-parity breaking models requires additional inputs to generate baryon asymmetry of the universe during the electroweak phase transition.Comment: 27 pages including 5 figures; Review article for Pramana: the Indian Journal of Physic