142 research outputs found
The Equation of State for Dense QCD and Quark Stars
We calculate the equation of state for degenerate quark matter to leading
order in hard-dense-loop (HDL) perturbation theory. We solve the
Tolman-Oppenheimer-Volkov equations to obtain the mass-radius relation for
dense quark stars. Both the perturbative QCD and the HDL equations of state
have a large variation with respect to the renormalization scale for quark
chemical potential below 1 GeV which leads to large theoretical uncertainties
in the quark star mass-radius relation.Comment: 7 pages, 3 figure
Quasilocality of joining/splitting strings from coherent states
Using the coherent state formalism we calculate matrix elements of the
one-loop non-planar dilatation operator of SYM between operators
dual to folded Frolov-Tseytlin strings and observe a curious scaling behavior.
We comment on the {\it qualitative} similarity of our matrix elements to the
interaction vertex of a string field theory. In addition, we present a solvable
toy model for string splitting and joining. The scaling behaviour of the matrix
elements suggests that the contribution to the genus one energy shift coming
from semi-classical string splitting and joining is small.Comment: 17 pages, 7 figures in 11 file
An infinite family of convex Brunnian links in
This paper proves that convex Brunnian links exist for every dimension by constructing explicit examples. These examples are three-component
links which are higher-dimensional generalizations of the Borromean rings.Comment: 10 pages, 4 figure
Canonical Coordinates and Meson Spectra for Scalar Deformed N=4 SYM from the AdS/CFT Correspondence
Five supersymmetric scalar deformations of the AdS_5xS^5 geometry are
investigated. By switching on condensates for the scalars in the N=4 multiplet
with a form which preserves a subgroup of the original R-symmetry, disk and
sphere configurations of D3-branes are formed in the dual supergravity
background. The analytic, canonical metric for each geometry is formulated and
the singularity structure is studied. Quarks are introduced into two of the
corresponding field theories using D7-brane probes and the pseudoscalar meson
spectrum is calculated. For one of the condensate configurations, a mass gap is
found and shown analytically to be present in the massless limit. It is also
found that there is a stepped spectrum with eigenstate degeneracy in the limit
of small quark masses. In the case of a second, similar deformation, it is
necessary to understand the full D3-D7 brane interaction to study the limit of
small quark masses. It is seen that simple solutions to the equations of motion
for the other three geometries are unlikely to exist.Comment: 16 pages, 7 figures, references added, typos correcte
Small, Dense Quark Stars from Perturbative QCD
As a model for nonideal behavior in the equation of state of QCD at high
density, we consider cold quark matter in perturbation theory. To second order
in the strong coupling constant, , the results depend sensitively on
the choice of the renormalization mass scale. Certain choices of this scale
correspond to a strongly first order chiral transition, and generate quark
stars with maximum masses and radii approximately half that of ordinary neutron
stars. At the center of these stars, quarks are essentially massless.Comment: ReVTeX, 5 pages, 3 figure
Spinorial Field and Lyra Geometry
The Dirac field is studied in a Lyra space-time background by means of the
classical Schwinger Variational Principle. We obtain the equations of motion,
establish the conservation laws, and get a scale relation relating the
energy-momentum and spin tensors. Such scale relation is an intrinsic property
for matter fields in Lyra background.Comment: 10 pages. Some misprints correcte
Non-planar ABJM Theory and Integrability
Using an effective vertex method we explicitly derive the two-loop dilatation
generator of ABJM theory in its SU(2)xSU(2) sector, including all non-planar
corrections. Subsequently, we apply this generator to a series of finite length
operators as well as to two different types of BMN operators. As in N=4 SYM, at
the planar level the finite length operators are found to exhibit a degeneracy
between certain pairs of operators with opposite parity - a degeneracy which
can be attributed to the existence of an extra conserved charge and thus to the
integrability of the planar theory. When non-planar corrections are taken into
account the degeneracies between parity pairs disappear hinting the absence of
higher conserved charges. The analysis of the BMN operators resembles that of
N=4 SYM. Additional non-planar terms appear for BMN operators of finite length
but once the strict BMN limit is taken these terms disappear.Comment: 1+26 pages, uses axodraw.sty. v2: typos fixed, references added. v3:
more typos fixed, minor correction
KK Parity in Warped Extra Dimension
We construct models with a Kaluza-Klein (KK) parity in a five- dimensional
warped geometry, in an attempt to address the little hierarchy problem present
in setups with bulk Standard Model fields. The lightest KK particle (LKP) is
stable and can play the role of dark matter. We consider the possibilities of
gluing two identical slices of 5D AdS in either the UV (IR-UV-IR model) or the
IR region (UV-IR-UV model) and discuss the model-building issues as well as
phenomenological properties in both cases. In particular, we find that the
UV-IR-UV model is not gravitationally stable and that additional mechanisms
might be required in the IR-UV-IR model in order to address flavor issues.
Collider signals of the warped KK parity are different from either the
conventional warped extra dimension without KK parity, in which the new
particles are not necessarily pair-produced, or the KK parity in flat universal
extra dimensions, where each KK level is nearly degenerate in mass. Dark matter
and collider properties of a TeV mass KK Z gauge boson as the LKP are
discussed.Comment: 35 pages, 11 figure
Optical Spectra of SNR Candidates in NGC 300
We present moderate-resolution (<5A) long-slit optical spectra of 51 nebular
objects in the nearby Sculptor Group galaxy NGC 300 obtained with the 2.3 meter
Advanced Technology Telescope at Siding Spring Observatory, Australia. Adopting
the criterion of [SII]/Ha>=0.4 to confirm supernova remnants (SNRs) from
optical spectra, we find that of 28 objects previously proposed as SNRs from
optical observations, 22 meet this criterion with six showing [SII]/Ha of less
than 0.4. Of 27 objects suggested as SNRs from radio data, four are associated
with the 28 previously proposed SNRs. Of these four, three (included in the 22
above) meet the criterion. In all, 22 of the 51 nebular objects meet the
[SII]/Ha criterion as SNRs while the nature of the remaining 29 objects remains
undetermined by these observations.Comment: Accepted for publication in Astrophysics & Space Scienc
Detection of Supernova Neutrinos by Neutrino-Proton Elastic Scattering
We propose that neutrino-proton elastic scattering, ,
can be used for the detection of supernova neutrinos in scintillator detectors.
Though the proton recoil kinetic energy spectrum is soft, with , and the scintillation light output from slow, heavily ionizing
protons is quenched, the yield above a realistic threshold is nearly as large
as that from . In addition, the measured proton
spectrum is related to the incident neutrino spectrum, which solves a
long-standing problem of how to separately measure the total energy and
temperature of , , , and .
The ability to detect this signal would give detectors like KamLAND and
Borexino a crucial and unique role in the quest to detect supernova neutrinos.Comment: 10 pages, 9 figures, revtex
- …