949 research outputs found
Positivity of High Density Effective Theory
We show that the effective field theory of low energy modes in dense QCD has
positive Euclidean path integral measure. The complexity of the measure of QCD
at finite chemical potential can be ascribed to modes which are irrelevant to
the dynamics at sufficiently high density. Rigorous inequalities follow at
asymptotic density. Lattice simulation of dense QCD should be possible using
the quark determinant calculated in the effective theory.Comment: 10 pages, Revised version, to appear in Rapid Communications of
Physical Review
Aspects of the Color Flavor Locking phase of QCD in the Nambu-Jona Lasinio approximation
We study two aspects of the CFL phase of QCD in the NJL approximation. The
first one is the issue of the dependence on \mu of the ultraviolet cutoff in
the gap equation, which is solved allowing a running coupling constant. The
second one is the dependence of the gap on the strange quark mass; using the
high density effective theory we perform an expansion in the parameter
(m_s/\mu)^2 after checking that its numerical validity is very good already at
first order.Comment: LaTeX file, 6 figure
Illuminating interfaces between phases of a U(1) x U(1) gauge theory
We study reflection and transmission of light at the interface between
different phases of a U(1) x U(1) gauge theory. On each side of the interface,
one can choose a basis so that one generator is free (allowing propagation of
light), and the orthogonal one may be free, Higgsed, or confined. However, the
basis on one side will in general be rotated relative to the basis on the other
by some angle alpha. We calculate reflection and transmission coefficients for
both polarizations of light and all 8 types of boundary, for arbitrary alpha.
We find that an observer measuring the behavior of light beams at the boundary
would be able to distinguish 4 different types of boundary, and we show how the
remaining ambiguity arises from the principle of complementarity
(indistinguishability of confined and Higgs phases) which leaves observables
invariant under a global electric/magnetic duality transformation. We also
explain the seemingly paradoxical behavior of Higgs/Higgs and confined/confined
boundaries, and clarify some previous arguments that confinement must involve
magnetic monopole condensation.Comment: RevTeX, 12 page
Quantumgroups in the Higgs Phase
In the Higgs phase we may be left with a residual finite symmetry group H of
the condensate. The topological interactions between the magnetic- and electric
excitations in these so-called discrete H gauge theories are completely
described by the Hopf algebra or quantumgroup D(H). In 2+1 dimensional space
time we may add a Chern-Simons term to such a model. This deforms the
underlying Hopf algebra D(H) into a quasi-Hopf algebra by means of a 3-cocycle
H. Consequently, the finite number of physically inequivalent discrete H gauge
theories obtained in this way are labelled by the elements of the cohomology
group H^3(H,U(1)). We briefly review the above results in these notes. Special
attention is given to the Coulomb screening mechanism operational in the Higgs
phase. This mechanism screens the Coulomb interactions, but not the
Aharonov-Bohm interactions. (Invited talk given by Mark de Wild Propitius at
`The III International Conference on Mathematical Physics, String Theory and
Quantum Gravity', Alushta, Ukraine, June 13-24, 1993. To be published in Theor.
Math. Phys.)Comment: 19 pages in Latex, ITFA-93-3
Neutrino processes in the condensed phase of color flavor locked quark matter
We study weak interactions involving Goldstone bosons in the neutral kaon
condensed phase of color flavor locked quark matter. We calculate the rates for
the dominant processes that contribute to the neutrino mean free p ath and to
neutrino production. A light state, with a mass , where and are the quark
chemical potential and superconducting gap respectively, is shown to play an
important role. We identify unique characteristics of weak interaction rates in
this novel phase and discuss how they might influence neutrino emission in core
collapse supernova and neutron stars.Comment: 21 pages, 4 figure
Charge Neutrality of the Color-Flavor Locked Phase from the Low Energy Effective Theory
We investigate the issue of charge neutrality of the CFL phase of dense
quark matter using the low energy effective theory of high density QCD. We show
that the local electric and color charge neutrality of the ground state in a
homogeneous color superconducting medium follows from its dynamics. We also
consider the situation of a spatially inhomogeneous medium, such as may be
found in a neutron star core. We find that spatial inhomogeneity results in the
generation of electric fields, and positrons/electrons may be present in the
ground state. We estimate the concentration of charged leptons in the ground
state to be and consider their influence on the
opacity of the medium with respect to the modified photons.Comment: typos corrected, this version to appear in PR
Effects of color superconductivity on the structure and formation of compact stars
We show that if color superconducting quark matter forms in hybrid or quark
stars it is possible to satisfy most of recent observational boundaries on
masses and radii of compact stellar objects. An energy of the order of
erg is released in the conversion from a (metastable) hadronic star
into a (stable) hybrid or quark star in presence of a color superconducting
phase. If the conversion occurs immediately after the deleptonization of the
proto-neutron star, the released energy can help Supernovae to explode. If the
conversion is delayed the energy released can power a Gamma Ray Burst. A delay
between the Supernova and the subsequent Gamma Ray Burst is possible, in
agreement with the delay proposed in recent analysis of astrophysical data.Comment: 4 pages, 2 figures. To be published in Phys.Rev.
Parametric pumping at finite frequency
We report on a first principles theory for analyzing the parametric electron
pump at a finite frequency. The pump is controlled by two pumping parameters
with phase difference . In the zero frequency limit, our theory predicts
the well known result that the pumped current is proportional to .
For the more general situation of a finite frequency, our theory predicts a
non-vanishing pumped current even when the two driving forces are in phase, in
agreement with the recent experimental results. We present the physical
mechanism behind the nonzero pumped current at , which we found to be
due to photon-assisted processes
Trends in cyclones in the high-latitude North Atlantic during 1979-2016
We report an increase in winter (DJF) cyclone densities in the areas around Svalbard and in northwestern Barents Sea and a decrease in cyclone densities in southeastern Barents Sea during 1979-2016. Despite high interannual variability, the trends are significant at the 90% confidence level. The changes appear as a result of a shift into a more meridional winter storm track in the high-latitude North Atlantic, associated with a positive trend in the Scandinavian Pattern. A significant decrease in the Brunt-Vaisala frequency east of Svalbard and a significant increase in the Eady Growth Rate north of Svalbard indicate increased baroclinicity, favouring enhanced cyclone activity in these regions. For the first time, we apply composite analysis to explicitly address regional consequences of these wintertime changes in the high-latitude North Atlantic. We find a tendency toward a warmer and more moist atmospheric state in the Barents Sea and over Svalbard with increased cyclone activity around Svalbard.Peer reviewe
Scalar-isoscalar excitation in dense quark matter
We study the spectrum of scalar-isoscalar excitations in the color-flavor
locked phase of dense quark matter. The sigma meson in this phase appears as a
four-quark state (of diquark and anti-diquark) with a well-defined mass and
extremely small width, as a consequence of it's small coupling to two pions.
The quark particle/hole degrees of freedom also contribute significantly to the
correlator just above the threshold 2\Delta where \Delta is the superconducting
gap.Comment: RevTeX, 11 pages, 4 fig
- âŠ