12,301 research outputs found
Clustering of vacancy defects in high-purity semi-insulating SiC
Positron lifetime spectroscopy was used to study native vacancy defects in
semi-insulating silicon carbide. The material is shown to contain (i) vacancy
clusters consisting of 4--5 missing atoms and (ii) Si vacancy related
negatively charged defects. The total open volume bound to the clusters
anticorrelates with the electrical resistivity both in as-grown and annealed
material. Our results suggest that Si vacancy related complexes compensate
electrically the as-grown material, but migrate to increase the size of the
clusters during annealing, leading to loss of resistivity.Comment: 8 pages, 5 figure
Color Superconductivity from Supersymmetry
A supersymmetric composite model of color superconductivity is proposed.
Quarks and diquarks are dynamically generated as composite fields by a newly
introduced strong gauge dynamics. It is shown that the condensation of the
scalar component of the diquark supermultiplet occurs when the chemical
potential becomes larger than some critical value. We believe that the model
well captures aspects of the diquark condensate behavior and helps our
understanding of the diquark dynamics in real QCD. The results obtained here
might be useful when we consider a theory composed of quarks and diquarks.Comment: 4 pages, 2 figures, An error in Eq.(10) correcte
Spontaneous Symmetry Breaking with Abnormal Number of Nambu-Goldstone Bosons and Kaon Condensate
We describe a class of relativistic models incorporating finite density of
matter in which spontaneous breakdown of continuous symmetries leads to a
lesser number of Nambu-Goldstone bosons than that required by the Goldstone
theorem. This class, in particular, describes the dynamics of the kaon
condensate in the color-flavor locked phase of high density QCD. We describe
the spectrum of low energy excitations in this dynamics and show that, despite
the presence of a condensate and gapless excitations, this system is not a
superfluid.Comment: 5 pages, 1 figure, REVTeX. Minor revisions made and 2 new references
added. To appear in Phys. Rev. Let
Inverse meson mass ordering in color-flavor-locking phase of high density QCD: erratum
We correct a mistake in the calculation of meson masses at large baryon
chemical potential made in hep-ph/9910491v2Comment: 2 pages, 1 figure, erratum to hep-ph/9910491v
(Non)-Renormalization of the Chiral Vortical Effect Coefficient
We show using diagramtic arguments that in some (but not all) cases, the
temperature dependent part of the chiral vortical effect coefficient is
independent of the coupling constant. An interpretation of this result in terms
of quantization in the effective 3 dimensional Chern-Simons theory is also
given. In the language of 3D dimensionally reduced theory, the value of the
chiral vortical coefficient is related to the formula . We also show that in the presence of dynamical gauge fields, the CVE
coefficient is not protected from renormalization, even in the large limit.Comment: 11 pages, 3 figures. Version 2 corrects an error and calculates
leading radiative correctio
Characterization of the nitrogen split interstitial defect in wurtzite aluminum nitride using density functional theory
We carried out Heyd-Scuseria-Ernzerhof hybrid density functional theory plane
wave supercell calculations in wurtzite aluminum nitride in order to
characterize the geometry, formation energies, transition levels and hyperfine
tensors of the nitrogen split interstitial defect. The calculated hyperfine
tensors may provide useful fingerprint of this defect for electron paramagnetic
resonance measurement.Comment: 5 pages, 3 figure
Classical and relativistic dynamics of supersolids: variational principle
We present a phenomenological Lagrangian and Poisson brackets for obtaining
nondissipative hydrodynamic theory of supersolids. A Lagrangian is constructed
on the basis of unification of the principles of non-equilibrium thermodynamics
and classical field theory. The Poisson brackets, governing the dynamics of
supersolids, are uniquely determined by the invariance requirement of the
kinematic part of the found Lagrangian. The generalization of Lagrangian is
discussed to include the dynamics of vortices. The obtained equations of motion
do not account for any dynamic symmetry associated with Galilean or Lorentz
invariance. They can be reduced to the original Andreev-Lifshitz equations if
to require Galilean invariance. We also present a relativistic-invariant
supersolid hydrodynamics, which might be useful in astrophysical applications.Comment: 22 pages, changed title and content, added reference
The shear viscosity of the non-commutative plasma
We compute the shear viscosity of the non-commutative N=4 super Yang-Mills
quantum field theory at strong coupling using the dual supergravity background.
Special interest derives from the fact that the background presents an
intrinsic anisotropy in space through the distinction of commutative and
non-commutative directions. Despite this anisotropy the analysis exhibits the
ubiquitous result \eta/s = 1/4\pi for two different shear channels. In order to
derive this result, we show that the boundary energy momentum tensor must
couple to the open string metric. As a byproduct we compute the renormalised
holographic energy momentum tensor and show that it coincides with one in the
commutative theory.Comment: 17 pages. v2: reference adde
- …