307 research outputs found
Wilson Loop-Loop Correlators in AdS/QCD
We calculate the expectation value of one circular Wilson loop and the
correlator of two concentric circular Wilson loops in AdS/QCD using the
modified AdS_5-metric given in Ref.[1]. The confinement properties of this
metric in AdS/QCD are analyzed and compared with QCD and Nambu-Goto theory in
four dimensions.Comment: 22 pages, 14 figure
Self Excitation of the Tunneling Scalar Field in False Vacuum Decay
A method to determine the quantum state of a scalar field after
-symmetric bubble nucleation has been developed recently. The method has
an advantage that it concisely gives us a clear picture of the resultant
quantum state. In particular, one may interpret the excitations as a particle
creation phenomenon just as in the case of particle creation in curved
spacetime. As an application, we investigate in detail the spectrum of quantum
excitations of the tunneling field when it undergoes false vacuum decay. We
consider a tunneling potential which is piece-wise quadratic, hence is simple
enough to allow us an analytical treatment. We find a strong dependence of the
excitation spectrum upon the shape of the potential on the true vacuum side. We
then discuss features of the excitation spectrum common to general tunneling
potentials not restricted to our simple model.Comment: 24 pages, uuencoded compressed postscript fil
Path Integral Bosonization of Massive GNO Fermions
We show the quantum equivalence between certain symmetric space sine-Gordon
models and the massive free fermions. In the massless limit, these fermions
reduce to the free fermions introduced by Goddard, Nahm and Olive (GNO) in
association with symmetric spaces . A path integral formulation is given
in terms of the Wess-Zumino-Witten action where the field variable takes
value in the orthogonal, unitary, and symplectic representations of the group
in the basis of the symmetric space. We show that, for example, such a path
integral bosonization is possible when the symmetric spaces are or . We also address the
relation between massive GNO fermions and the nonabelian solitons, and explain
the restriction imposed on the fermion mass matrix due to the integrability of
the bosonic model.Comment: 11 page
Generalized Conformal Quantum Mechanics of D0-brane
We study the generalized conformal quantum mechanics of the probe D0-brane in
the near horizon background of the bound state of source D0-branes. We
elaborate on the relationship of such model to the M theory in the light cone
frame.Comment: 14 pages, RevTeX, revised version with added references to appear in
Phys. Rev.
Relation between Tunneling and Particle Production in Vacuum Decay
The field-theoretical description of quantum fluctuations on the background
of a tunneling field is revisited in the case of a functional
Schrodinger approach. We apply this method in the case when quantum
fluctuations are coupled to the field through a mass-squared term,
which is 'time-dependent' since we include the dynamics of . The
resulting mode functions of the fluctuation field, which determine the quantum
state after tunneling, display a previously unseen resonance effect when their
mode number is comparable to the curvature scale of the bubble. A detailed
analysis of the relation between the excitations of the field about the true
vacuum (interpreted as particle creation) and the phase shift coming from
tunneling is presented.Comment: 20 pages, 4 figures, submitted to PR
String Theory on Dp-plane waves
We study the spectrum of solvable string models on plane waves descending
from non-conformal Dp-brane geometries. We mainly focus on S-dual F1/D1-waves
in type IIB and type I/heterotic 10D superstrings. We derive the Kaluza-Klein
spectrum of N=1,2 10D supergravities on D1/F1-waves. We compute helicity
supertraces counting multiplicities and R-charges of string excitations in the
plane wave geometry. The results are compared against the expectations coming
from gauge/supergravity descriptions. In the type I case, the Klein, Annulus
and Moebius one-loop amplitudes are computed for ten-dimensional D1-waves. We
test the consistency of the open string descendant by showing that after
modular transformations to the closed string channel, the three amplitudes
combine themselves to reconstruct a complete square (|B>+|C>)^2. Tadpole
conditions are also discussed.Comment: 22 pages, Minor corrections, References adde
Possible Effects of Noncommutative Geometry on Weak CP Violation and Unitarity Triangles
Possible effects of noncommutative geometry on weak CP violation and
unitarity triangles are discussed by taking account of a simple version of the
momentum-dependent quark mixing matrix in the noncommutative standard model. In
particular, we calculate nine rephasing invariants of CP violation and
illustrate the noncommutative CP-violating effect in a couple of charged
D-meson decays. We also show how inner angles of the deformed unitarity
triangles are related to CP-violating asymmetries in some typical B_d and B_s
transitions into CP eigenstates. B-meson factories are expected to help probe
or constrain noncommutative geometry at low energies in the near future.Comment: RexTev 16 pages. Modifications made. References added. Accepted for
publication in Phys. Rev.
Natural Theories of Ultra-Low Mass PNGB's: Axions and Quintessence
We consider the Wilson Line PNGB which arises in a U(1)^N gauge theory,
abstracted from a latticized, periodically compactified extra dimension U(1).
Planck scale breaking of the PNGB's global symmetry is suppressed, providing
natural candidates for the axion and quintessence. We construct an explicit
model in which the axion may be viewed as the 5th component of the U(1)_Y gauge
field in a 1+4 latticized periodically compactified extra dimension. We also
construct a quintessence PNGB model where the ultra-low mass arises from
Planck-scale suppressed physics itself.Comment: 20 pages, fixed typo and reference
Superstrings on NS5 backgrounds, deformed AdS3 and holography
We study a non-standard decoupling limit of the D1/D5-brane system, which
interpolates between the near-horizon geometry of the D1/D5 background and the
near-horizon limit of the pure D5-brane geometry. The S-dual description of
this background is actually an exactly solvable two-dimensional (worldsheet)
conformal field theory: {null-deformed SL(2,R)} x SU(2) x T^4 or K3. This model
is free of strong-coupling singularities. By a careful treatment of the
SL(2,R), based on the better-understood SL(2,R) / U(1) coset, we obtain the
full partition function for superstrings on SL(2,R) x SU(2) x K3. This allows
us to compute the partition functions for the J^3 and J^2 current-current
deformations, as well as the full line of supersymmetric null deformations,
which links the SL(2,R) conformal field theory with linear dilaton theory. The
holographic interpretation of this setup is a renormalization-group flow
between the decoupled NS5-brane world-volume theory in the ultraviolet (Little
String Theory), and the low-energy dynamics of super Yang--Mills string-like
instantons in six dimensions.Comment: JHEP style, 59 pages, 1 figure; v2: minor changes, to appear in JHE
The QCD Phase Structure at High Baryon Density
We consider the possibility that color deconfinement and chiral symmetry
restoration do not coincide in dense baryonic matter at low temperature. As a
consequence, a state of massive "constituent" quarks would exist as an
intermediate phase between confined nuclear matter and the plasma of deconfined
massless quarks and gluons. We discuss the properties of this state and its
relation to the recently proposed quarkyonic matter.Comment: 17 pages, 9 figure
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