119344257
Infrared behavior of the dispersion relations in high-temperature scalar QED
We investigate the infrared properties of the next-to-leading-order dispersion relations in scalar quantum electrodynamics at high temperature in the context of hard-thermal-loop perturbation theory. Specifically, we determine the damping rate and the energy for scalars with ultrasoft momenta. We show by explicit calculations that an early external-momentum expansion, before the Matsubara sum is performed, gives exactly the same result as a late one. The damping rate is obtained up to fourth order included in the ultrasoft momentum and the energy up to second order. The damping rate is found sensitive in the infrared whereas the energy is not.
15732602
Infrared Sensitivity in Damping Rate for Very Soft Moving Fermions in Finite Temperature QED
We calculate the fermion damping rate to second order in powers of the external momentum $p$ in the context of QED at finite temperature using the hard-thermal-loop (HTL) summation scheme. We find that the coefficient of order $p^{2}$ is divergent in the infrared whereas the two others are finite. This result suggests that the htl-based pertubation is infrared sensitive at next-to-leading order.
120280840
FOUR-SPINON CONTRIBUTION TO THE DYNAMIC STRUCTURE FACTOR IN THE ANTIFERROMAGNETIC HEISENBERG MODEL
14826247
A potential infrared problem with the damping rates for gluons with soft momentum in hot QCD
Abstract We calculate the damping rate γl for longitudinal gluons with zero momentum in high-temperature QCD and show that some of its contributing terms are infrared divergent. This is in contrast with the expectation that this damping rate is to be equal to the corresponding one γt for transverse gluons which is known to be finite. Our calculation was motivated by the fact that similar divergent terms occur when we calculated in a previous work γt to order p2, p being the momentum of the gluon. After we present our results, we briefly discuss them.
117310527
Nonperturbative Studies in Quantum Field Theory.
54663418
Phenomenology of a light cold dark matter two-singlet model
We study the implications of phenomenological processes on a two-singlet extension of the Standard Model we introduced in a previous work to describe light cold dark matter. We look into
67797503
First lattice QCD estimate of the g(D* D pi) coupling
We present the results of the first lattice QCD study of the strong coupling gDDπ. From our simulations in the quenched approximation, we obtain gDDπ = 18.8 ± 2.3 +1.1 −2.0 and bc = 0.67 ±0.08 +0.04 −0.06 . Whereas previous theoretical studies gave different predictions, our result favours a large value for bc. It agrees very well with the recent experimental value by CLEO. ˆ varies very little with the heavy mass and we find in the infinite mass limit b∞ = 0.69(18).
119095917
Heavy to light vector meson semileptonic decays
New (preliminary) results for the form factors relevant for the semileptonic decays of heavy pseudoscalar to a light vector meson are presented. In particular, we discuss the form factors for D -->K* and B -->rho modes.
13436243
Flavour matters in leptogenesis
We give analytic approximations to the baryon asymmetry produced by thermal leptogenesis with hierarchical right-handed neutrinos. Our calculation includes flavour-dependent washout processes and CP violation in scattering, and neglects gauge interactions and finite temperature corrections. Our approximate formulae depend upon the three CP asymmetries in the individual lepton flavours as well as on three flavour-dependent efficiency factors. We show that the commonly used expressions for the lepton asymmetry, which depend on the total CP asymmetry and one single efficiency factor, may fail to reproduce the correct lepton asymmetry in a number of cases. We illustrate the importance of using the flavour-dependent formulae in the context of a two right-handed neutrino model.
14322693
Constraints on both bilinear and trilinear R-parity violating couplings from neutrino laboratories and astrophysics data
Abstract We consider neutrino masses generated at tree level and at one loop, through fermion–sfermion loop diagrams, in the MSSM with R-parity violation. Using the (3×3) mass and mixing matrices for three generations of neutrinos and the present experimental results on neutrinos from laboratories and astrophysics simultaneously, we put bounds on both trilinear ( λ ijk , λ ′ ijk ) and bilinear ( μ e , μ μ , μ τ ) R-parity-violating couplings.
18139806
MULTIBODY NEUTRINO EXCHANGE IN A NEUTRON STAR : NEUTRINO SEA AND BORDER EFFECTS
Abstract The interaction due to the exchange of massless neutrinos between neutrons is a long-range force. Border effects on this multibody exchange inside a dense core are studied and computed analytically in 1 + 1 dimensions. We demonstrate in this work that a proper treatment of the star's border effect automatically incorporates the condensate contribution as a consequence of the appropriate boundary conditions for the neutrino Feynman propagator inside the star. The total multibody exchange contribution is infrared-safe and vanishes exactly in 1 + 1 dimensions. The general conclusion of this work is that the border effect does not modify the result that neutrino exchange is infrared-safe. This toy model prepares the ground and gives the tools for the study of the realistic 3 + 1 star.