38 research outputs found
Superconductivity by long-range color magnetic interaction in high-density quark matter
We argue that in quark matter at high densities, the color magnetic field
remains unscreened and leads to the phenomenon of color superconductivity.
Using the renormalization group near the Fermi surface, we find that the
long-range nature of the magnetic interaction changes the asymptotic behavior
of the gap at large chemical potential qualitatively. We find
, where is the
small gauge coupling. We discuss the possibility of breaking rotational
symmetry by the formation of a condensate with nonzero angular momentum, as
well as interesting parallels to some condensed matter systems with long-range
forces.Comment: 14 pages, REVTEX, uses eps
The Crystallography of Color Superconductivity
We develop the Ginzburg-Landau approach to comparing different possible
crystal structures for the crystalline color superconducting phase of QCD, the
QCD incarnation of the Larkin-Ovchinnikov-Fulde-Ferrell phase. In this phase,
quarks of different flavor with differing Fermi momenta form Cooper pairs with
nonzero total momentum, yielding a condensate that varies in space like a sum
of plane waves. We work at zero temperature, as is relevant for compact star
physics. The Ginzburg-Landau approach predicts a strong first-order phase
transition (as a function of the chemical potential difference between quarks)
and for this reason is not under quantitative control. Nevertheless, by
organizing the comparison between different possible arrangements of plane
waves (i.e. different crystal structures) it provides considerable qualitative
insight into what makes a crystal structure favorable. Together, the
qualitative insights and the quantitative, but not controlled, calculations
make a compelling case that the favored pairing pattern yields a condensate
which is a sum of eight plane waves forming a face-centered cubic structure.
They also predict that the phase is quite robust, with gaps comparable in
magnitude to the BCS gap that would form if the Fermi momenta were degenerate.
These predictions may be tested in ultracold gases made of fermionic atoms. In
a QCD context, our results lay the foundation for a calculation of vortex
pinning in a crystalline color superconductor, and thus for the analysis of
pulsar glitches that may originate within the core of a compact star.Comment: 41 pages, 13 figures, 1 tabl
Infection by the castrating parasitic nematode <i>Sphaerularia bombi </i>changes gene expression in <i>Bombus terrestris </i>bumblebee queens
Parasitism can result in dramatic changes in host phenotype, which are themselves
underpinned by genes and their expression. Understanding how hosts respond at the molecular
level to parasites can therefore reveal the molecular architecture of an altered host phenotype.
The entomoparasitic nematode Sphaerularia bombi is a parasite of bumblebee (Bombus) hosts
where it induces complex behavioural changes and host castration. To examine this interaction
at the molecular level, we performed genome-wide transcriptional profiling using RNA-Seq of S.
bombi-infected Bombus terrestris queens at two critical time-points: during and just after
overwintering diapause. We found that infection by S. bombi affects the transcription of genes
underlying host biological processes associated with energy usage, translation, and circadian
rhythm. We also found that the parasite affects the expression of immune genes, including
members of the Toll signaling pathway providing evidence for a novel interaction between the
parasite and the host immune response. Taken together, our results identify host biological
processes and genes affected by an entomoparasitic nematode providing the first steps towards
a molecular understanding of this ecologically important host-parasite interaction
Comments on the Quark Content of the Scalar Meson
Based on the measurements of we determine, in
a model independent way, the allowed content in the scalar meson
. We find that, on the one hand, if this isoscalar resonance is a
pure state [ , a very
large -annihilation term will be needed to accommodate . On the other hand, the component of
should be small enough to avoid excessive induced
from the external -emission. Measurement of production in the
decay will be useful to test the above picture. For the
decay which is kinematically barely or even not
allowed, depending on the mass of , we find that the finite width
effect of plays a crucial role on the resonant three-body decay
.Comment: 12 pages, 2 figure
Scalar Particles in Lattice QCD
We report a project to study scalar particles by lattice QCD simulations.
After a brief introduction of the current situation of lattice study of the
sigma meson, we describe our numerical simulations of scalar mesons,
and . We observe a low sigma mass, , for
which the disconnected diagram plays an important role. For the kappa meson, we
obtain higher mass than the experimental value, i.e., .Comment: 4 figures, to be published in Proceedings of `International Symposium
on Hadron Spectroscopy, Chiral Symmetry and Relativistic Description of Bound
Systems' (in a series of KEK proceedings
Low Energy Theory for 2 flavors at High Density QCD
We construct the effective Lagrangian describing the low energy excitations
for Quantum Chromodynamics with two flavors at high density. The non-linear
realization framework is employed to properly construct the low energy
effective theory. The light degrees of freedom, as required by 't Hooft anomaly
conditions, contain massless fermions which we properly include in the
effective Lagrangian. We also provide a discussion of the linearly realized
Lagrangian.Comment: 17 pages, RevTeX format, references added. To appear in Phys. Rev.
Magnetic catalysis and anisotropic confinement in QCD
The expressions for dynamical masses of quarks in the chiral limit in QCD in
a strong magnetic field are obtained. A low energy effective action for the
corresponding Nambu-Goldstone bosons is derived and the values of their decay
constants as well as the velocities are calculated. The existence of a
threshold value of the number of colors , dividing the theories with
essentially different dynamics, is established. For the number of colors , an anisotropic dynamics of confinement with the confinement
scale much less than and a rich spectrum of light glueballs is
realized. For of order or larger, a conventional confinement
dynamics takes place. It is found that the threshold value grows
rapidly with the magnetic field [ for ]. In contrast to QCD with a nonzero baryon density, there are no
principal obstacles for checking these results and predictions in lattice
computer simulations.Comment: 10 pages, 1 figure. REVTeX. Minor correction. To appear in Phys. Rev.
Emergence of Skyrme crystal in Gross-Neveu and 't Hooft models at finite density
We study two-dimensional, large field theoretic models (Gross-Neveu
model, 't Hooft model) at finite baryon density near the chiral limit. The same
mechanism which leads to massless baryons in these models induces a breakdown
of translational invariance at any finite density. In the chiral limit baryonic
matter is characterized by a spatially varying chiral angle with a wave number
depending only on the density. For small bare quark masses a sine-Gordon kink
chain is obtained which may be regarded as simplest realization of the Skyrme
crystal for nuclear matter. Characteristic differences between confining and
non-confining models are pointed out.Comment: 27 pages, 11 figures, added reference, corrected sig
Baryon number violation, baryogenesis and defects with extra dimensions
In generic models for grand unified theories(GUT), various types of baryon
number violating processes are expected when quarks and leptons propagate in
the background of GUT strings. On the other hand, in models with large extra
dimensions, the baryon number violation in the background of a string is not
trivial because it must depend on the mechanism of the proton stabilization. In
this paper we argue that cosmic strings in models with extra dimensions can
enhance the baryon number violation to a phenomenologically interesting level,
if the proton decay is suppressed by the mechanism of localized wavefunctions.
We also make some comments on baryogenesis mediated by cosmological defects. We
show at least two scenarios will be successful in this direction. One is the
scenario of leptogenesis where the required lepton number conversion is
mediated by cosmic strings, and the other is the baryogenesis from the decaying
cosmological domain wall. Both scenarios are new and have not been discussed in
the past.Comment: 20pages, latex2e, comments and references added, to appear in PR