366 research outputs found
Gauge Theory of the String Geodesic Field
A relativistic string is usually represented by the Nambu-Goto action in
terms of the extremal area of a 2-dimensional timelike submanifold of Minkowski
space. Alternatively, a family of classical solutions of the string equation of
motion can be globally described in terms of the associated geodesic field. In
this paper we propose a new gauge theory for the geodesic field of closed and
open strings. Our approach solves the technical and conceptual problems
affecting previous attempts to describe strings in terms of local field
variables. The connection between the geodesic field, the string current and
the Kalb-Ramond gauge potential is discussed and clarified. A non-abelian
generalization and the generally covariant form of the model are also
discussed.Comment: 38 pages, PHYZZX, UTS-DFT-92-2
Medium Modification of The Pion-Pion Interaction at Finite Density
We discuss medium modifications of the unitarized pion-pion interaction in
the nuclear medium. We incorporate both the effects of chiral symmetry
restoration and the influence of collective nuclear pionic modes originating
from the p-wave coupling of the pion to delta-hole configurations. We show in
particular that the dropping of the sigma meson mass significantly enhances the
low energy structure created by the in-medium collective pionic modes.Comment: 26 pages, 7 figures included, Latex fil
Pseudo-unitary symmetry and the Gaussian pseudo-unitary ensemble of random matrices
Employing the currently discussed notion of pseudo-Hermiticity, we define a
pseudo-unitary group. Further, we develop a random matrix theory which is
invariant under such a group and call this ensemble of pseudo-Hermitian random
matrices as the pseudo-unitary ensemble. We obtain exact results for the
nearest-neighbour level spacing distribution for (2 X 2) PT-symmetric
Hamiltonian matrices which has a novel form, s log (1/s) near zero spacing.
This shows a level repulsion in marked distinction with an algebraic form in
the Wigner surmise. We believe that this paves way for a description of varied
phenomena in two-dimensional statistical mechanics, quantum chromodynamics, and
so on.Comment: 9 pages, 2 figures, LaTeX, submitted to the Physical Review Letters
on August 20, 200
Scalar density fluctuation at critical end point in NJL model
Soft mode near the critical end point in the phase diagram of two-flavor
Nambu--Jona-Lasinio (NJL) model is investigated within the leading 1/N_c
approximation with N_c being the number of the colors. It is explicitly shown
by studying the spectral function of the scalar channel that the relevant soft
mode is the scalar density fluctuation, which is coupled with the quark number
density, while the sigma meson mode stays massive.Comment: 9 pages, 4 figure
Weyl Invariant Formulation of Flux-Tube Solution in the Dual Ginzburg-Landau Theory
The flux-tube solution in the dual Ginzburg-Landau (DGL) theory in the
Bogomol'nyi limit is studied by using the manifestly Weyl invariant form of the
DGL Lagrangian. The dual gauge symmetry is extended to , and
accordingly, there appear three different types of the flux-tube. The string
tension for each flux-tube is calculated analytically and is found to be the
same owing to the Weyl symmetry. It is suggested that the flux-tube can be
treated in quite a similar way with the Abrikosov-Nielsen-Olesen vortex in the
U(1) Abelian Higgs theory except for various types of flux-tube.Comment: 12 pages, revtex, no figur
Collective Excitations in High-Temperature Superconductors
Collective, low-energy excitations in quasi-two-dimensional d-wave
superconductors are analyzed. While the long-range Coulomb interaction shifts
the charge-density-wave and phase modes up to the plasma energy, the
spin-density-wave excitation that arises due to a strong local
electron-electron repulsion can propagate as a damped collective mode within
the superconducting energy gap. It is suggested that these excitations are
relevant to high-Tc superconductors, close to the antiferromagnetic phase
boundary, and may explain some of the exotic features of the experimentally
observed spectral-density and neutron-scattering data.Comment: 5 jolly page
What does engram encode?: Heterogeneous memory engrams for different aspects of experience
Long-lasting synaptic changes within the neuronal network mediate memory. Neurons bearing such physical traces of memory (memory engram cells) are often equated with neurons expressing immediate early genes (IEGs) during a specific experience. However, past studies observed the expression of different IEGs in non-overlapping neurons or synaptic plasticity in neurons that do not express a particular IEG. Importantly, recent studies revealed that distinct subsets of neurons expressing different IEGs or even IEG negative-(yet active) neurons support different aspects of memory or computation, suggesting a more complex nature of memory engram cells than previously thought. In this short review, we introduce studies revealing such heterogeneous composition of the memory engram and discuss how the memory system benefits from it
QCD Critical Points and Their Associated Soft Modes
The mean-field level calculation shows that the QCD matter can have multiple
critical points incorporating the color superconductivity under charge
neutrality constraint due to the repulsive vector interaction; this actually
implies that the QCD matter is very soft for a simultaneous formation of
diquark and chiral condensates coupled with the baryonic density. Dynamical
density fluctuations are analyzed as possible soft modes around the QCD
critical point using dissipative relativistic fluid dynamics. It is found that
the entropy fluctuation solely gets enhanced while the sound modes due to
mechanical density fluctuations are strongly attenuated around the QCD CP,
which may suggest a suppression or even total disappearance of Mach cone at the
CP.Comment: 8 pages, 3 figures. Talk presented at Yukawa International workshop
"New Frontiers in QCD 2010 --- Exotic Hadron Systems and Dense Matter ---"
(NFQCD10), Jan. 18(Mon.)-Mar.19(Fri), 2010, Yukawa Institute for Theoretical
Physics, Kyoto, Japa
From QFT to DCC
A quantum field theoretical model for the dynamics of the disoriented chiral
condensate is presented. A unified approach to relate the quantum field theory
directly to the formation, decay and signals of the DCC and its evolution is
taken. We use a background field analysis of the O(4) sigma model keeping
one-loop quantum corrections (quadratic order in the fluctuations). An
evolution of the quantum fluctuations in an external, expanding metric which
simulates the expansion of the plasma, is carried out. We examine, in detail,
the amplification of the low momentum pion modes with two competing effects,
the expansion rate of the plasma and the transition rate of the vacuum
configuration from a metastable state into a stable state.We show the effect of
DCC formation on the multiplicity distributions and the Bose-Einstein
correlations.Comment: 34 pages, 10 figure
Quantum inference of states and processes
The maximum-likelihood principle unifies inference of quantum states and
processes from experimental noisy data. Particularly, a generic quantum process
may be estimated simultaneously with unknown quantum probe states provided that
measurements on probe and transformed probe states are available. Drawbacks of
various approximate treatments are considered.Comment: 7 pages, 4 figure
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