962,667 research outputs found
Fermion dispersion in axion medium
The interaction of a fermion with the dense axion medium is investigated for
the purpose of finding an axion medium effect on the fermion dispersion. It is
shown that axion medium influence on the fermion dispersion under astrophysical
conditions is negligible small if the correct Lagrangian of the axion-fermion
interaction is used.Comment: 5 pages, 1 figure, to appear in International Journal of Modern
Physics
Comment on "Scaling of the quasiparticle spectrum for d-wave superconductors"
In a recent Letter Simon and Lee suggested a scaling law for thermodynamic
and kinetic properties of superconductors with lines of gap nodes. However
their crossover parameter between the bulk dominated regime and the vortex
dominated regime is different from that found in our paper (N.B. Kopnin and
G.E. Volovik, JETP Lett., {\bf 64}, 690 (1996); see also cond-mat/9702093). We
discuss the origin of the disagreement.Comment: submitted to Physical Review Letters as "Comment" to the paper by
S.H. Simon and P.A. Lee, Phys. Rev. Lett., 78 (1997) 1548 (cond-mat/9611133
The Nambu sum rule and the relation between the masses of composite Higgs bosons
We review the known results on the bosonic spectrum in various NJL models
both in the condensed matter physics and in relativistic quantum field theory
including He-B, He-A, the thin films of superfluid He-3, and QCD
(Hadronic phase and the Color Flavor Locking phase). Next, we calculate bosonic
spectrum in the relativistic model of top quark condensation suggested in
\cite{Miransky}. In all considered cases the sum rule appears that relates the
masses (energy gaps) of the bosonic excitations in each channel
with the mass (energy gap) of the condensed fermion as . Previously this relation was established by Nambu in \cite{Nambu}
for He-B and for the s - wave superconductor. We generalize this relation
to the wider class of models and call it the Nambu sum rule. We discuss the
possibility to apply this sum rule to various models of top quark condensation.
In some cases this rule allows to calculate the masses of extra Higgs bosons
that are the Nambu partners of the 125 GeV Higgs.Comment: Latex, 15 page
One-dimensional multicomponent Fermi gas in a trap: quantum Monte Carlo study
One-dimensional world is very unusual as there is an interplay between
quantum statistics and geometry, and a strong short-range repulsion between
atoms mimics Fermi exclusion principle, fermionizing the system. Instead, a
system with a large number of components with a single atom in each, on the
opposite acquires many bosonic properties. We study the ground-state properties
a multi-component Fermi gas trapped in a harmonic trap by fixed-node diffusion
Monte Carlo method. We investigate how the energetic properties (energy,
contact) and correlation functions (density profile and momentum distribution)
evolve as the number of components is changed. It is shown that the system
fermionizes in the limit of strong interactions. Analytical expression are
derived in the limit of weak interactions within the local density
approximation for arbitrary number of components and for one plus one particle
using an exact solution.Comment: 15 pages, 5 figure
Wavefunctions and counting formulas for quasiholes of clustered quantum Hall states on a sphere
The quasiholes of the Read-Rezayi clustered quantum Hall states are
considered, for any number of particles and quasiholes on a sphere, and for any
degree k of clustering. A set of trial wavefunctions, that are zero-energy
eigenstates of a k+1-body interaction, and so are symmetric polynomials that
vanish when any k+1 particle coordinates are equal, is obtained explicitly and
proved to be both complete and linearly independent. Formulas for the number of
states are obtained, without the use of (but in agreement with) conformal field
theory, and extended to give the number of states for each angular momentum. An
interesting recursive structure emerges in the states that relates those for k
to those for k-1. It is pointed out that the same numbers of zero-energy states
can be proved to occur in certain one-dimensional models that have recently
been obtained as limits of the two-dimensional k+1-body interaction
Hamiltonians, using results from the combinatorial literature.Comment: 9 pages. v2: minor corrections; additional references; note added on
connection with one-dimensional Hamiltonians of recent interes
Non-abelian statistics of half-quantum vortices in p-wave superconductors
Excitation spectrum of a half-quantum vortex in a p-wave superconductor
contains a zero-energy Majorana fermion. This results in a degeneracy of the
ground state of the system of several vortices. From the properties of the
solutions to Bogoliubov-de-Gennes equations in the vortex core we derive the
non-abelian statistics of vortices identical to that for the Moore-Read
(Pfaffian) quantum Hall state.Comment: 5 pages, 3 figures, REVTeX, epsf. Reference adde
Stimulated Raman backscattering of laser radiation in deep plasma channels
Stimulated Raman backscattering (RBS) of intense laser radiation confined by
a single-mode plasma channel with a radial variation of plasma frequency
greater than a homogeneous-plasma RBS bandwidth is characterized by a strong
transverse localization of resonantly-driven electron plasma waves (EPW). The
EPW localization reduces the peak growth rate of RBS and increases the
amplification bandwidth. The continuum of non-bound modes of backscattered
radiation shrinks the transverse field profile in a channel and increases the
RBS growth rate. Solution of the initial-value problem shows that an
electromagnetic pulse amplified by the RBS in the single-mode deep plasma
channel has a group velocity higher than in the case of homogeneous-plasma
Raman amplification. Implications to the design of an RBS pulse compressor in a
plasma channel are discussed.Comment: 11 pages, 3 figures; submitted to Physics of Plasma
Magnetic resonance within vortex cores in the B phase of superfluid He
We investigate a magnetic susceptibility of vortices in the B phase of
multicomponent triplet superfluid He focusing on a contribution of bound
fermionic states localized within vortex cores. Several order parameter
configurations relevant to different types of quantized vortices in He B
are considered. It is shown quite generally that an ac magnetic susceptibility
has a sharp peak at the frequency corresponding to the energy of interlevel
spacing in the spectrum of bound fermions. We suggest that measuring of a
magnetic resonance within vortex cores can provide a direct probe of a discrete
spectrum of bound vortex core excitations
Black-hole horizon and metric singularity at the brane separating two sliding superfluids
An analog of black hole can be realized in the low-temperature laboratory.
The horizon can be constructed for the `relativistic' ripplons (surface waves)
living on the brane. The brane is represented by the interface between two
superfluid liquids, 3He-A and 3He-B, sliding along each other without friction.
Similar experimental arrangement has been recently used for the observation and
investigation of the Kelvin-Helmholtz type of instability in superfluids
(cond-mat/0111343). The shear-flow instability in superfluids is characterized
by two critical velocities. The lowest threshold measured in recent experiments
(cond-mat/0111343) corresponds to appearance of the ergoregion for ripplons. In
the modified geometry this will give rise to the black-hole event horizon in
the effective metric experienced by ripplons. In the region behind the horizon,
the brane vacuum is unstable due to interaction with the higher-dimensional
world of bulk superfluids. The time of the development of instability can be
made very long at low temperature. This will allow us to reach and investigate
the second critical velocity -- the proper Kelvin-Helmholtz instability
threshold. The latter corresponds to the singularity inside the black hole,
where the determinant of the effective metric becomes infinite.Comment: LaTeX file, 12 pages, 3 Figures, version accepted in JETP Letter
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