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Departing from standard slow-roll conditions is one way of putting the inflationary paradigm to test, and constraining the dynamics of the inflaton field with a constant-rate of roll of the inflaton field, a.k.a. the constant-roll scenario, is one way of exploring such deviation from the standard slow-roll dynamics. In this manuscript we explore such a possibility in a variant inflationary scenario, known as Warm Inflation. We construct and derive the conditions for having constant-roll WI models where inflation lasts at least for 60 $e-$folds, gracefully exits the constant-roll inflation phase, and maintains near thermal equilibrium of the system which is an essential feature of WI in the slow-roll regime. We show that while certain models of WI (the ones with dissipative coefficient as a function of temperature alone) can accommodate constant-roll dynamics, others (with dissipative coefficient as a function of temperature and the inflaton field both) fail to maintain thermal equilibrium once the constant-roll condition is imposed and hence cannot produce a constant-roll WI phase., Comment: Double-column, 14 pages, 6 figures, v2: a few references added, version accepted for publication in Physical Review D

Slow-roll of the inflaton field defines the standard dynamics of the inflationary epoch. However, the inflationary system deviates from slow-roll when it encounters an extremely flat region of the inflaton potential, and enters a phase dubbed Ultra slow roll. In this article, we explore the possibility of realizing an Ultra slow-roll phase in a particularly interesting inflationary scenario, called Warm Inflation. In the Warm inflationary scenario a thermalized, sub-dominant radiation bath coexists with the inflaton energy density as an effect of dissipative dynamics. We show in this article that though the background dynamics indicate Ultra slow-roll when the potential becomes extremely flat, in Warm Inflation models, where the dissipation coefficient is a sole function of the temperature of the radiation bath, the system fails to maintain the thermal equilibrium as soon as it enters the Ultra slow-roll phase. As thermal equilibrium is a key feature of Warm Inflation, and as it is not yet known how to deal with Warm Inflation without thermal equilibrium, we could not analyze such systems any further in this article. However, we demonstrate that brief periods of Ultra slow-roll phase, which smoothly ends into standard slow-roll, can be accommodated in WI models where the dissipation coefficient is not only a function of the temperature of the radiation bath but also depends on the amplitude of the inflaton field. We theoretically determine the criteria of successfully embedding Ultra slow-roll in WI while the system remain in thermal equilibrium, and also demonstrate numerically that such short Ultra slow-roll phases can indeed be embedded in specific Warm Inflation models which comply with the theoretically determined criteria., Comment: 10 pages, double column, 10 figures, v2: minor modification to text, references added, title modified according to PRD Editor's suggestion, accepted for publication in Physical Review D

It is anticipated that a number of techniques to measure the top quark mass at the LHC will yield m_top with uncertainties of about 0.5-1 percent. These uncertainties are mostly theoretical; they are usually estimated using parton shower Monte Carlo programs whose reliability at this level of precision is difficult to assess. The goal of this paper is to contrast those estimates with the results of NLO QCD computations for a few observables, often discussed in the context of high-precision top quark mass measurements at the LHC. In particular, we study the NLO QCD corrections to the invariant mass distribution of a charged lepton and a B-meson in lepton+jets channels. In the dilepton channel we investigate the invariant mass distribution of a charged lepton and a b-jet, the average energy of the two leptons and the average energy of the b-jets from top decays., Comment: 18 pages, 8 figures, 3 tables

We extend previous computations of the second order QCD corrections to semileptonic b \to c inclusive transitions, to the case where the charged lepton in the final state is massive. This allows accurate description of b \to c \tau \bar \nu_\tau decays. We review techniques used in the computation of O(\alpha_s^2) corrections to inclusive semileptonic b \to c transitions and present extensive numerical studies of O(\alpha_s^2) QCD corrections to b \to c l \bar \nu_l decays, for l =e, \tau., Comment: 30 pages, 4 figures, 5 tables

We study how the rotation of a classical magnetic field influences vacuum birefringence. In spite of the fact that solutions of the wave equation depend in a non-trivial way on the relative magnitude of the strength of vacuum birefringence and the angular rotation frequency of the magnetic field, the induced ellipticity of the light ray does not depend on the magnetic field angular rotation frequency. Hence, in contrast to recent claims, the result of the PVLAS experiment cannot be explained by conventional non-linear quantum electrodynamics., Comment: 8 pages, revtex