2,756 research outputs found
Are there plasminos in superconductors?
Hot and/or dense, normal-conducting systems of relativistic fermions exhibit
a particular collective excitation, the so-called plasmino. We compute the
one-loop self-energy, the dispersion relation and the spectral density for
fermions interacting via attractive boson exchange. It is shown that plasminos
also exist in superconductors.Comment: 15 pages, 14 figures, revte
Ultrasoft Quark Damping in Hot QCD
We determine the quark damping rates in the context of next-to-leading order
hard-thermal-loop summed perturbation of high-temperature QCD where weak
coupling is assumed. The quarks are ultrasoft. Three types of divergent
behavior are encountered: infrared, light-cone and at specific points
determined by the gluon energies. The infrared divergence persists and is
logarithmic whereas the two others are circumvented.Comment: 16 page
Resonant Relaxation in Electroweak Baryogenesis
We compute the leading, chiral charge-changing relaxation term in the quantum
transport equations that govern electroweak baryogenesis using the closed time
path formulation of non-equilibrium quantum field theory. We show that the
relaxation transport coefficients may be resonantly enhanced under appropriate
conditions on electroweak model parameters and that such enhancements can
mitigate the impact of similar enhancements in the CP-violating source terms.
We also develop a power counting in the time and energy scales entering
electroweak baryogenesis and include effects through second order in ratios
of the small and large scales. We illustrate the implications of the
resonantly enhanced terms using the Minimal
Supersymmetric Standard Model, focusing on the interplay between the
requirements of baryogenesis and constraints obtained from collider studies,
precision electroweak data, and electric dipole moment searches.Comment: 30 pages plus appendices, 7 figure
Multiexcitons confined within a sub-excitonic volume: Spectroscopic and dynamical signatures of neutral and charged biexcitons in ultrasmall semiconductor nanocrystals
The use of ultrafast gating techniques allows us to resolve both spectrally
and temporally the emission from short-lived neutral and negatively charged
biexcitons in ultrasmall (sub-10 nm) CdSe nanocrystals (nanocrystal quantum
dots). Because of forced overlap of electronic wave functions and reduced
dielectric screening, these states are characterized by giant interaction
energies of tens (neutral biexcitons) to hundreds (charged biexcitons) of meV.
Both types of biexcitons show extremely short lifetimes (from sub-100
picoseconds to sub-picosecond time scales) that rapidly shorten with decreasing
nanocrystal size. These ultrafast relaxation dynamics are explained in terms of
highly efficient nonradiative Auger recombination.Comment: 5 pages, 4 figures, to be published in Phys. Rev.
Quadrupole transitions near interface: general theory and application to atom inside a planar cavity
Quadrupole radiation of an atom in an arbitrary environment is investigated
within classical as well as quantum electrodynamical approaches. Analytical
expressions for decay rates are obtained in terms of Green function of Maxwell
equations. The equivalence of both approaches is shown. General expressions are
applied to analyze the quadrupole decay rate of an atom placed between two half
spaces with arbitrary dielectric constant. It is shown that in the case when
the atom is close to the surface, the total decay rate is inversely
proportional to the fifth power of distance between an atom and a plane
interface.Comment: 18 pages, 7 figure
Field quantization and squeezed states generation in resonators with time-dependent parameters
The problem of electromagnetic field quantization is usually considered in textbooks under the assumption that the field occupies some empty box. The case when a nonuniform time-dependent dielectric medium is confined in some space region with time-dependent boundaries is studied. The basis of the subsequent consideration is the system of Maxwell's equations in linear passive time-dependent dielectric and magnetic medium without sources
Infrared Behavior of High-Temperature QCD
The damping rate \gamma_t(p) of on-shell transverse gluons with ultrasoft
momentum p is calculated in the context of next-to-leading-order
hard-thermal-loop-summed perturbation of high-temperature QCD. It is obtained
in an expansion to second order in p. The first coefficient is recovered but
that of order p^2 is found divergent in the infrared. Divergences from
light-like momenta do also occur but are circumvented. Our result and method
are critically discussed, particularly regarding a Ward identity obtained in
the literature. When enforcing the equality between \gamma_t(0) and
\gamma_l(0), a rough estimate of the magnetic mass is obtained. Carrying a
similar calculation in the context of scalar quantum electrodynamics shows that
the early ultrasoft-momentum expansion we make has little to do with the
infrared sensitivity of the result.Comment: REVTEX4, 55 page
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