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Baryon mass splittings are analyzed in terms of a simple model with general
pairwise interactions. At present, the $\Delta$ masses are poorly known from
experiments. Improvement of these data would provide an opportunity to make a
significant test of our understanding of electromagnetic and quark-mass
contributions to hadronic masses. The problem of determining resonance masses
from scattering and production data is discussed.
|
hep-ph/9207215
| 727,383 |
We show that, the lattice regularization of chiral gauge theories proposed by
Kaplan, when applied to a (2+1)-dimensional domain wall, produces a
(1+1)-dimensional theory at low energy even if gauge anomaly produced by chiral
fermions does not cancel. But the corresponding statement is not true in higher
dimensions.
|
hep-th/9207014
| 727,384 |
We point out that the production cross section of $pp\to V'V$, with
$V'=W',Z'$ and $V=W,Z$ is a useful diagnostic of $V'$ gauge couplings at future
hadron colliders. For $M_{Z'}\simeq1$ TeV it would allow determination of
combinations of $Z'$ gauge couplings to the quarks to around 10 percent. An
analysis of the extraction of gauge couplings from the complementary tests:
forward-backward asymmetry, rare decays $pp\to V'\to f_1{\bar f_2}V$, and the
production cross section $pp\to V'V$ is given in a model-independent framework.
Four ratios of charges are needed to characterize a general gauge theory with
an additional family-independent $U_1'$ factor. We show that there are four
functions of these ratios observable at hadron colliders, but for projected SSC
and LHC luminosities only two combinations can be extracted. These yield a
significant discrimination between interesting GUT-motivated models. Clean
tests of whether a new $W'$ couples to right-handed currents, of the ratio
$g_R/g_L$ of gauge couplings, and of the non-abelian vertex in left-right
symmetric models are described.
|
hep-ph/9207216
| 727,384 |
It is shown that for non-hyperbolic real quadratic polynomials topological
and quasisymmetric conjugacy classes are the same. By quasiconformal rigidity,
each class has only one representative in the quadratic family, which proves
that hyperbolic maps are dense.
|
math/9207219
| 727,385 |
The phase diagram of a lattice microemulsion model proposed by Ciach, H{\o}ye
and Stell is studied using mean-field theory and Monte Carlo simulations.
Surfactant directional degrees of freedom are summed out exactly before
mean-field theory is applied, and the resulting phase diagrams are much
improved compared with previous mean-field results. The critical line and
tricritical point is located using Monte Carlo simulations and finite size
scaling.
|
cond-mat/9207006
| 727,385 |
A discrete charge transfer in a small tunnel junction where Coulomb
interactions are important can excite electron-hole pairs near the Fermi level.
We use a simple model to study the associated nonequilibrium properties and
found two novel effects: (i) for junctions with electrodes of the same
electronic properties, a leakage current exists within the Coulomb gap even
when the environmental impedance is infinite; (ii) for junctions with
electrodes of different electronic properties, the differential conductance
diverges when a net interaction between conduction electrons is attractive, and
it is strongly suppressed for a net repulsive interaction.
|
cond-mat/9207007
| 727,385 |
To any pair ( M , theta ) where M is a family of finite subsets of N compact
in the pointwise topology, and 0<theta < 1 , we associate a Tsirelson-type
Banach space T_M^theta . It is shown that if the Cantor-Bendixson index of M is
greater than n and theta >{1/n} then T_M^theta is reflexive. Moreover, if the
Cantor-Bendixson index of M is greater than omega then T_M^theta does not
contain any l^p, while if the Cantor-Bendixson index of M is finite
thenT_M^theta contains some l^p or c_o . In particular, if M ={ A subset N :
|A| leq n } and {1/n}<theta <1 then T_M^theta is isomorphic to some l^p .
|
math/9207206
| 727,385 |
In this paper we investigate how the phase diagram of a U(1) symmetric
Higgs-Yukawa system depends on the scalar self coupling $\lambda$. The phase
diagram of similar models with continuous symmetry were extensively studied in
the infinite scalar self coupling $\lambda=\infty$ limit. Recent analytical and
numerical calculations at zero self coupling showed qualitatively different
phase diagram, raising the question of the $\lambda$ dependence of the phase
diagram. Here we use analytical (large $N_f$, perturbative and mean field)
approximations as well as numerical simulations to investigate the system.
|
hep-lat/9207006
| 727,385 |
Noncompact groups, similar to those that appeared in various supergravity
theories in the 1970's, have been turning up in recent studies of string
theory. First it was discovered that moduli spaces of toroidal compactification
are given by noncompact groups modded out by their maximal compact subgroups
and discrete duality groups. Then it was found that many other moduli spaces
have analogous descriptions. More recently, noncompact group symmetries have
turned up in effective actions used to study string cosmology and other
classical configurations. This paper explores these noncompact groups in the
case of toroidal compactification both from the viewpoint of low-energy
effective field theory, using the method of dimensional reduction, and from the
viewpoint of the string theory world sheet. The conclusion is that all these
symmetries are intimately related. In particular, we find that Chern--Simons
terms in the three-form field strength $H_{\mu\nu\rho}$ play a crucial role.
|
hep-th/9207016
| 727,385 |
We discuss the Isgur-Wise function $\xi (y)$ in the small velocity (SV) limit
within the QCD sum rule method. The behavior of $\xi (y)$ in the SV limit is
sensitive to the particular form of the duality relations used to decontaminate
the sum rule predictions from the continuum contribution. Peculiarities of the
duality relations in the problem at hand are revealed. It is shown that the
proper requirements of duality and angular isotropy for S wave states lead to
an unambiguous form of the sum rules for the Isgur-Wise function. We illustrate
the constraints due to these requirements using a toy model of the harmonic
oscillator. The slope parameter and the shape of $\xi (y)$ are determined.
|
hep-ph/9207217
| 727,386 |
This review is devoted to the application of bosonization techniques to two
dimensional QCD. We start with a description of the ``abelian bosonization".
The methods of the abelian bosonization are applied to several examples like
the Thirring model, the Schwinger model and QCD$_2$. The failure of this scheme
to handle flavored fermions is explained. Witten's non-abelian bosonization
rules are summarized including the generalization to the case of fermions with
color and flavor degrees of freedom. We discuss in details the bosonic version
of the mass bilinear of colored-flavored fermions in various schemes. The color
group is gauged and the full bosonized version of massive multiflavor QCD is
written down. The strong coupling limit is taken in the ``product scheme" and
then in the $U(N_F\times N_C)$ scheme. Once the multiflavor $QCD_2$ action in
the interesting region of the low energies is written down, we extract the
semiclassical low lying baryonic spectrum. First classical soliton solutions of
the bosonic action are derived. Quantizing the flavor space around those
classical solutions produces the masses as well as the flavor properties of the
two dimensional baryons. In addition low lying multibaryonic solutions are
presented, as well as wave functions and matrix elements of interest, like
$q\bar q$ content.
|
hep-th/9207017
| 727,386 |
We carry out Monte Carlo simulations of the uniformly frustrated 3d XY model
as a model for vortex line fluctuations in a high Tc superconductor. A density
of vortex lines of f=1/25 is considered. We find two sharp phase transitions.
The low T phase is an ordered vortex line lattice. The high T normal phase is a
vortex line liquid with much entangling, cutting, and loop excitations. An
intermediate phase is found which is characterized as a vortex line liquid of
disentangled lines. In this phase, the system displays superconducting
properties in the direction parallel to the magnetic field, but normal behavior
in planes perpendicular to the magnetic field.
|
cond-mat/9207008
| 727,386 |
We show that within the framework of the minimal $SU(5)$ supergravity model,
radiatively-induced electroweak symmetry breaking and presently available
experimental lower bounds on nucleon decay, impose severe constraints on the
available parameter space of the model which correspond to fine-tuning of the
model parameters of over two orders of magnitude. Furthermore, a
straightforward calculation of the cosmic relic density of neutralinos ($\chi$)
gives $\Omega_\chi h^2\gg1$ for most of the allowed parameter space in this
model, although small regions may still be cosmologically acceptable. We
finally discuss how the {\it no-scale flipped $SU(5)$ supergravity model}
avoids naturally the above troubles and thus constitutes a good candidate for
the low-energy effective supergravity model.
|
hep-ph/9207219
| 727,386 |
This manual describes version 1.0 of the Monte Carlo event generator KROWIG
for deep inelastic lepton hadron scattering at HERA. KROWIG combines the
implementation of QED radiative corrections in KRONOS with the QCD parton
showers and cluster fragmentation of HERWIG.
|
hep-ph/9207220
| 727,386 |
If the present baryon-asymmetry is due to a Planck or GUT-scale matter
asymmetry then baryon- or lepton-number violating processes are constrained by
the condition that they do not subsequently erase this asymmetry. We present a
revision of the analysis of sphaleron baryon-number violating processes in the
standard model including lepton-mass effects. We find the surprising result
that a GUT-scale matter-asymmetry can survive the $B$ and $L$ violating
sphaleron interactions even though ($B- L$) is conserved and equals zero for
all temperatures. We extend the analysis to cover the minimal supersymmetric
standard model (MSSM) and also derive the constraints on the R-parity violating
couplings in extensions of the MSSM. In the case of the baryon number violating
dimension 4 operators we find, contrary to current wisdom, that the resulting
bounds can be avoided completely because of a residual lepton-flavour number
conservation; in the case of lepton number violating operators we find the
bounds are flavour dependent and can be avoided completely in definite flavour
channels. We also consider how the bounds are modified in the case there is a
Grand Unified extension of the supersymmetric model which introduces new lepton
flavour violating couplings.
|
hep-ph/9207221
| 727,387 |
To investigate order-order interfaces, we perform multimagnetical Monte Carlo
simulations of the $2D$ and $3D$ Ising model. Stringent tests of the numerical
methods are performed by reproducing with high precision exact $2D$ results. In
the physically more interesting $3D$ case we estimate the amplitude $F^s_0$ of
the critical interfacial tension.
|
hep-lat/9207007
| 727,387 |
Two series of W-algebras with two generators are constructed from chiral
vertex operators of a free field representation. If $c = 1 - 24k$, there exists
a W(2,3k) algebra for k in $Z_{+}/2$ and a W(2,8k) algebra for k in $Z_{+}/4$.
All possible lowest-weight representations, their characters and fusion rules
are calculated proving that these theories are rational. It is shown, that
these non-unitary theories complete the classification of all rational theories
with effective central charge $c_{eff} = 1$. The results are generalized to the
case of extended supersymmetric conformal algebras.
|
hep-th/9207019
| 727,387 |
We analyze numerically the critical properties of a two-dimensional
discretized random surface with extrinsic curvature embedded in a
three-dimensional space. The use of the toroidal topology enables us to enforce
the non-zero external extension without the necessity of defining a boundary
and allows us to measure directly the string tension. We show that a phase
transition from the crumpled phase to the smooth phase observed earlier for a
spherical topology appears also for a toroidal surface for the same finite
value of the coupling constant of the extrinsic curvature term. The phase
transition is characterized by the vanishing of the string tension. We discuss
the possible non-trivial continuum limit of the theory, when approaching the
critical point. Numerically we find a value of the critical exponent $\n$ to be
between .38 and .42. The specific heat, related to the extrinsic curvature term
seems not to diverge (or diverge slower than logarithmically) at the critical
point.
|
hep-lat/9207008
| 727,387 |
The pair interaction between magnetic flux lines in a semi-infinite slab of
an anisotropic type-II superconductor in an external field is derived in the
London limit. The case where the applied field is normal to the
superconductor/vacuum interface is considered. The presence of stray fields
near the surface leads to an additional contribution to the repulsive
interaction between flux lines that vanishes exponentially with the distance
from the interface. The pair interaction is used to obtain the continuum
elastic energy of a distorted semi-infinite flux-line array. The presence of
the superconductor/vacuum interface yields surface contributions to the
compressional and tilt elastic constants.
|
cond-mat/9207009
| 727,387 |
We describe an iterative scheme which allows us to calculate any multi-loop
correlator for the complex matrix model to any genus using only the first in
the chain of loop equations. The method works for a completely general
potential and the results contain no explicit reference to the couplings. The
genus $g$ contribution to the $m$--loop correlator depends on a finite number
of parameters, namely at most $4g-2+m$. We find the generating functional
explicitly up to genus three. We show as well that the model is equivalent to
an external field problem for the complex matrix model with a logarithmic
potential.
|
hep-th/9207020
| 727,387 |
Within the Quantum Action Principle framework we show the perturbative
renormalizability of previously proposed topological lagrangian \`a la
Witten-Fujikawa describing polymers, then we perform a 2 loop computation. The
theory turns out to have the same predictive power of De Gennes theory, even
though its running coupling constants exhibit a very peculiar behaviour.
Moreover we argue that the theory presents two phases , a topological and a non
topological one.
|
hep-th/9207021
| 727,387 |
We calculate the low-lying part of the spectrum of the $Z_3$-symmetrical
chiral Potts quantum chain in its self-dual and integrable versions, using
numerical diagonalisation of the hamiltonian for $N \leq 12$ sites and
extrapolation $N \ra \infty$. From the sequences of levels crossing we show
that the massive phases have oscillatory correlation functions. We calculate
the wave vector scaling exponent. In the high-temperature massive phase the
pattern of the low-lying levels can be explained assuming the existence of two
particles, with $Z_3$-charge $Q\!=\!1$ and $Q\!=\!2$, and their scattering
states. In the superintegrable case the $Q\!=\!2$-particle has twice the mass
of the $Q\!=\!1$-particle. Exponential convergence in $N$ is observed for the
single particle gaps, while power convergence is seen for the scattering
levels. In the high temperature limit of the self-dual model the parity
violation in the particle dispersion relation is equivalent to the presence of
a macroscopic momentum $P_m = \pm \vph/3$, where $\vph$ is the chiral angle.
|
hep-th/9207022
| 727,387 |
Short distance physics involving virtual top and charm quarks contributes to
$\mu^+$ (and $\mu^-$) polarization in the decay $K^+ \rightarrow \pi^+ \mu^+
\mu^-$. Measurement of the parity violating asymmetry $(\Gamma_R -
\Gamma_L)/(\Gamma_R + \Gamma_L)$, where $\Gamma_R$ and $\Gamma_L$ are the rates
to produce right and left-handed $\mu^+$, may provide valuable information on
the unitarity triangle. The parity violating asymmetry also gets a contribution
from Feynman diagrams with two photon intermediate states. We estimate this two
photon contribution to the asymmetry and discuss briefly the two photon
contribution to time reversal odd asymmetries that involve both the $\mu^+$ and
$\mu^-$ polarizations.
|
hep-ph/9207222
| 727,387 |
This report is a combined version of two talks presented by the authors at
the Edinburgh $b$-physics Workshop, December 1991. It presents the ideas of
heavy quark symmetry and gives an introduction to some applications. The
references indicate where to go for more information: they are not intended to
be complete, nor do they necessarily refer to the original work on any
particular subject.
|
hep-ph/9207223
| 727,387 |
We study the chiral rings in N=2 and N=4 superconformal algebras. The chiral
primary states of N=2 superconformal algebras realized over hermitian triple
systems are given. Their coset spaces G/H are hermitian symmetric which can be
compact or non-compact. In the non-compact case, under the requirement of
unitarity of the representations of G we find an infinite set of chiral primary
states associated with the holomorphic discrete series representations of G.
Further requirement of the unitarity of the corresponding N=2 module truncates
this infinite set to a finite subset. The chiral primary states of the N=2
superconformal algebras realized over Freudenthal triple systems are also
studied. These algebras have the special property that they admit an extension
to N=4 superconformal algebras with the gauge group SU(2)XSU(2)XU(1). We
generalize the concept of the chiral rings to N=4 superconformal algebras. We
find four different rings associated with each sector (left or right moving).
We also show that our analysis yields all the possible rings of N=4
superconformal algebras.
|
hep-th/9207023
| 727,387 |
Recently, it was suggested that the 17 keV neutrino does not mix with the
electron neutrino in the weak interactions. Instead, the $\beta$ decay mode
involving the 17 keV neutrino is induced by a completely new interaction,
presumably mediated by leptoquarks. A previous model for the ``unmixed 17 keV
neutrino" suffers from difficulties with experimental data and cosmological
constraints. Here we present an alternative model in which these difficulties
are resolved.
|
hep-ph/9207224
| 727,388 |
The leading and the subleading Landau singularities in affine Toda field
theories are examined in some detail. Formulae describing the subleading simple
pole structure of box diagrams are given explicitly. This leads to a new and
nontrivial test of the conjectured exact S-matrices for these theories. We show
that to the one-loop level the conjectured S-matrices of the $A_n$ Toda family
reproduce the correct singularity structure, leading as well as subleading, of
the field theoretical amplitudes. The present test has the merit of being
independent of the details of the renormalisations.
|
hep-th/9207025
| 727,388 |
For the special case of the quantum group $SL_q (2,{\bf C})\ (q= \exp \pi
i/r,\ r\ge 3)$ we present an alternative approach to quantum gauge theories in
two dimensions. We exhibit the similarities to Witten's combinatorial approach
which is based on ideas of Migdal. The main ingredient is the Turaev-Viro
combinatorial construction of topological invariants of closed, compact
3-manifolds and its extension to arbitrary compact 3-manifolds as given by the
authors in collaboration with W. Mueller.
|
hep-th/9207026
| 727,388 |
The values of $\sin (2 \alpha)$ and $\sin (2 \beta)$, where $\alpha$ and
$\beta$ are angles of the unitarity triangle, will be readily measured in a B
factory (and maybe also in hadron colliders). We study the standard model
constraints in the $\sin (2 \alpha) - \sin (2 \beta)$ plane. We use the results
from recent analyses of $f_B$ and $\tau_b|V_{cb}|^2$ which take into account
heavy quark symmetry considerations. We find $\sin (2 \beta) \geq 0.15$ and
most likely $\sin (2 \beta) \roughly{>} 0.6$, and emphasize the strong
correlations between $\sin (2 \alpha)$ and $\sin (2 \beta)$. Various schemes
for quark mass matrices allow much smaller areas in the $\sin (2 \alpha) - \sin
(2 \beta)$ plane. We study the schemes of Fritzsch, of Dimopoulos, Hall and
Raby, and of Giudice, as well as the ``symmetric CKM'' idea, and show how CP
asymmetries in B decays will crucially test each of these schemes.
|
hep-ph/9207225
| 727,388 |
Following Symanzik we argue that the Schr\"odinger functional in lattice
gauge theories without matter fields has a well-defined continuum limit. Due to
gauge invariance no extra counter terms are required. The Schr\"odinger
functional is, moreover, accessible to numerical simulations. It may hence be
used to study the scaling properties of the theory and in particular the
evolution of the renormalized gauge coupling from low to high energies. A
concrete proposition along this line is made and the necessary perturbative
analysis of the Schr\"odinger functional is carried through to 1-loop order.
|
hep-lat/9207009
| 727,388 |
A finite-size scaling technique is applied to the SU(2) gauge theory (without
matter fields) to compute a non-perturbatively defined running coupling
alpha(q) for a range of momenta q given in units of the string tension K. We
find that already at rather low q, the evolution of alpha(q) is well described
by the 2-loop approximation to the Callan-Symanzik beta-function. At the
highest momentum reached, q=20 sqrt(K), we obtain alpha_MSbar(q)=0.187 +/-
0.005 +/- 0.009 for the running coupling in the MSbar scheme of dimensional
regularization.
|
hep-lat/9207010
| 727,388 |
We show that the N=2 open string describes a theory of self-dual Yang Mills
(SDYM) in (2,2) dimensions. The coupling to the closed sector is described by
SDYM in a Kahler background, with the Yang-Mills fields providing a source term
to the self-duality equation in the gravity sector. The four-point S-matrix
elements of the theory vanish, so the tree-level unitarity constraints leading
to the Chan-Paton construction are relaxed. By considering more general
group-theory ansatze the N=2 string can be written for any gauge group, and not
just the classical groups allowed for the bosonic and N=1 strings. Such ad hoc
group-theory factors can not be appended to the closed N=2 string, explaining
why the Z_n closed N=2 strings are trivial extensions of the Z_1 theory.
|
hep-th/9207024
| 727,388 |
On the example of nonabelian Toda type theory associated with the Lie
superalgebra $osp(2|4)$ we show that this integrable dynamical system is
relevant to a black hole background metric in the corresponding target space.
In the even sector the model under consideration reduces to the exactly
solvable conformal theory (nonabelian $B_2$ Toda system) in the presence of a
black hole recently proposed in the article "Black holes from non-abelian Toda
theories" by the last two authors (hep-th 9203039).
|
hep-th/9207027
| 727,388 |
It is shown that the probability distribution $P(\lambda)$ for the effective
cosmological constant is sharply peaked at $\lambda=0$ in stochastic (or
"fifth-time") stabilized quantum gravity. The effect is similar to the
Baum-Hawking mechanism, except that it comes about due to quantum fluctuations,
rather than as a zeroth-order (in $\hbar$) semiclassical effect.
|
hep-th/9207028
| 727,388 |
It is shown that a technicolor theory containing a color-octet technipion,
usually denoted by $P^{0'}_{8}$, will give rise to an enhancement of $t \bar t$
production at the Tevatron, LHC and SSC, via the process $gg \rightarrow
P^{0'}_{8} \rightarrow t \bar t$. The relevant cross-sections are computed
taking into account the large lower bound on the top mass coming from the "top
search" experiments at LEP and CDF.
At the LHC and SSC, the signal is found to be comparable to the QCD
background, making the process quite accesible.
|
hep-ph/9207226
| 727,388 |
We examine how the abilities of an SDC-like detector to discover and identify
the origin of a new neutral gauge boson are affected by $Z_1-Z_2 $ mixing and
by variations in detector parameters such as lepton pair mass resolution,
particle identification efficiency, and rapidity coverage. Also examined is the
sensitivity of these results to variations in structure function uncertainties
and uncertainties in the machine integrated luminosity. Such considerations are
of importance when dealing with the issues of detector descoping and design.
|
hep-ph/9207229
| 727,388 |
A systematic numerical technique for the calculation of unstable periodic
orbits in the stadium billiard is presented. All the periodic orbits up to
order $p=11$ are calculated and then used to calculate the average Lyapunov
exponent and the topological entropy. Applications to semiclassical
quantization and to experiments in mesoscopic systems and microwave cavities
are noted.
|
cond-mat/9207010
| 727,388 |
We investigate the time evolution of the heteropolymer model introduced by
Iori, Marinari and Parisi to describe some of the features of protein folding
mechanisms. We study how the (folded) shape of the chain evolves in time. We
find that for short times the mean square distance (squared) between chain
configurations evolves according to a power law, $D \sim t ^\nu$. We discuss
the influence of the quenched disorder (represented by the randomness of the
coupling constants in the Lennard-Jones potential) on value of the critical
exponent. We find that $\nu$ decreases from $\frac{2}{3}$ to $\frac{1}{2}$ when
the strength of the quenched disorder increases.
|
hep-lat/9207011
| 727,388 |
We study the electroweak phase transition in a supersymmetric version of the
Standard Model, in which a gauge singlet superfield is added to the Higgs
sector. We show that the order of the transition is determined by the trilinear
soft supersymmetry breaking terms rather than by the $O ( m^{3} T )$ term in
the 1-loop, $T\neq0$ corrections. This fact removes the Standard Model upper
bound on the Higgs mass, $ m_{H} < 55 GeV$, coming from the requirement that
baryon asymmetry is not washed out by anomalous electroweak processes. We
perform a numerical analysis of parameter space including in the effective
potential top-stop contribution to 1-loop radiative corrections. We find that
this model is compatible with the preservation of baryon asymmetry for masses
of the lightest scalar up to about 170 GeV.
|
hep-ph/9207227
| 727,388 |
$Vect(N)$, the algebra of vector fields in $N$ dimensions, is studied. Some
aspects of local differential geometry are formulated as $Vect(N)$
representation theory. There is a new class of modules, {\it conformal fields},
whose restrictions to the subalgebra $sl(N+1) \subset Vect(N)$ are
finite-dimensional $sl(N+1)$ representations. In this regard they are simpler
than tensor fields. Fock modules are also constructed. Infinities, which are
unremovable even by normal ordering, arise unless bosonic and fermionic degrees
of freedom match.
|
hep-th/9207029
| 727,388 |
We apply the optimization procedure based on the Principle of Minimal
Sensitivity to the third-order calculation of $\R$. The effective couplant
remains finite, freezing to a value $\alpha_s/\pi = 0.26$ at low energies.
Using Poggio-Quinn-Weinberg smearing we find good agreement between theory and
experiment right down to zero energy.
|
hep-ph/9207228
| 727,388 |
Conformal fields are a recently discovered class of representations of the
algebra of vector fields in $N$ dimensions. Invariant first-order differential
operators (exterior derivatives) for conformal fields are constructed.
|
hep-th/9207030
| 727,388 |
We introduce two new sets of invariant functions of quark mass matrices,
which express the constraints on these mass matrices due to knowledge of the
quark mixing matrix. These invariants provide a very simple method to test
candidate forms for mass matrices.
|
hep-ph/9207230
| 727,388 |
Sets of commuting charges constructed from the current of a U(1) Kac-Moody
algebra are found. There exists a set S_n of such charges for each positive
integer n > 1; the corresponding value of the central charge in the
Feigin-Fuchs realization of the stress tensor is c = 13-6n-6/n. The charges in
each series can be written in terms of the generators of an exceptional
W-algebra.
|
hep-th/9207031
| 727,389 |
It is shown that the sl(2,C) KZ equation for (half-) integer isospins
recovers, up to a gauge transformation, the matrix system for Virasoro algebra
singular vectors of Bauer et al. In the case of Kac-Kazhdan spins the general
(infinite matrix) KZ system is truncated due to the decoupling of the A^(1)_1
singular vectors. This suggests an algorithm converting Malikov-Feigin-Fuks
singular vectors into Virasoro ones.
|
hep-th/9207032
| 727,389 |
In order that discrete symmetries should not be violated by gravitational
effects, it is necessary to gauge them. In this paper we discuss the gauging of
$\Z_N$ from the breaking of a high energy $SU(N)$ gauge symmetry, and derive
consistency conditions for the resulting discrete symmetry fr om the
requirement of anomaly cancellation in the parent symmetry. These results are
then applied to a detailed analysis of the possible discrete symmetries
forbidding proton decay in the minimal supersymmetric standard model.
|
hep-ph/9207231
| 727,389 |
The particle detector model consisting of a harmonic oscillator coupled to a
scalar field in $1+1$ dimensions is investigated in the inertial case. The same
approach is then used in the accelerating case. The absence of radiation from a
uniformly accelerated detector in a stationnary state is discussed and
clarified.
|
hep-th/9207033
| 727,389 |
We present a numerical study of a model of pattern formation following a
convective instability in a non-Boussinesq fluid. It is shown that many of the
features observed in convection experiments conducted on $CO_{2}$ gas can be
reproduced by using a generalized two-dimensional Swift-Hohenberg equation. The
formation of hexagonal patterns, rolls and spirals is studied, as well as the
transitions and competition among them. We also study nucleation and growth of
hexagonal patterns and find that the front velocity in this two dimensional
model is consistent with the prediction of marginal stability theory for one
dimensional fronts.
|
cond-mat/9207011
| 727,389 |
A detailed investigation of the theoretical ambiguities present in the QCD
description of photon production in $e^+e^-$ annihilation is given. It is
pointed out that in a well-defined perturbative analysis it is necessary to
subtract the quark-photon collinear singularities. This subtraction requires
the introduction of an unphysical parameter in the perturbative part of the
cross section. The subtracted term is factored into non-perturbative
fragmentation function. The dependence on the unphysical parameter cancels in
the sum of non-perturbative and perturbative parts. It is pointed out that for
$E_{\gamma}\le \sqrt{s}/(2(1+\epsilon_c))$ the non-perturbative contributions
are suppressed. Using a general purpose next-to-leading order Monte Carlo
program, we calculate various physical quantities that were measured in LEP
experiments recently.
|
hep-ph/9207232
| 727,389 |
We calculate the decay rates for $\piee$, $\etaee$ and $\etamumu$ in chiral
perturbation theory. The linear combination of counterterms necessary to render
these amplitudes finite is fixed by the recently measured branching fraction
for $\etamumu$. We find $\Br(\piee ) = 7\pm 1\times 10^{-8}$ and $\Br(\etaee
)=5\pm 1\times 10^{-9}$.
|
hep-ph/9207233
| 727,389 |
The subject considered in this paper has, at least, three points of interest.
Suppose that we have a sequence of one-dimensional analytic varieties in a
domain in $\Bbb C^n$. The cluster of this sequence consists from all points in
the domains such that every neighbourhood of such points intersects with
infinitely many different varieties. The first question is: what analytic
properties does the cluster inherit from varieties? We give a sufficient
criterion when the cluster contains an analytic disk, but it follows from
examples of Stolzenberg and Wermer that, in general, clusters can contain no
analytic disks. So we study algebras of continuous function on clusters, which
can be approximated by holomorphic functions or polynomials, and show that this
algebras possess some analytic properties in all but explicitly pathological
and uninteresting cases. Secondly, we apply and results about clusters to
polynomial hulls and maximal functions, finding remnants of analytic structures
there too. And, finally, due to more and more frequent appearances of analytic
disks as tools in complex analysis, it seems to be interesting to look at their
sequences to establish terminology, basic notation and properties.
|
math/9207202
| 727,389 |
In his famous 1981 paper, Lempert proved that given a point in a strongly
convex domain the complex geodesics (i.e., the extremal disks) for the
Kobayashi metric passing through that point provide a very useful fibration of
the domain. In this paper we address the question whether, given a smooth
complex Finsler metric on a complex manifold, it is possible to give purely
differential geometric properties of the metric ensuring the existence of such
a fibration in complex geodesics of the manifold. We first discuss at some
length the notion of holomorphic sectional curvature for a complex Finsler
metric; then, using the differential equation of complex geodesics we obtained
in a previous paper, we show that for every pair (point, tangent vector) there
is a (only a segment if the metric is not complete) complex geodesic passing
through the point tangent to the given vector iff the Finsler metric is
K\"ahler, has constant holomorphic sectional curvature -4 and satisfies a
simmetry condition on the curvature tensor. Finally, we show that a complex
Finsler metric of constant holomorphic sectional curvature -4 satisfying the
given simmetry condition on the curvature is necessarily the Kobayashi metric.
|
math/9207201
| 727,389 |
We compute the cosmic relic (dark matter) density of the lightest
supersymmetric particle (LSP) in the framework of minimal $N=1$ Supergravity
models with radiative breaking of the electroweak gauge symmetry. To this end,
we re--calculate the cross sections for all possible annihilation processes for
a general, mixed neutralino state with arbitrary mass. Our analysis includes
effects of all Yukawa couplings of third generation fermions, and allows for a
fairly general set of soft SUSY breaking parameters at the Planck scale. We
find that a cosmologically interesting relic density emerges naturally over
wide regions of parameter space. However, the requirement that relic
neutralinos do not overclose the universe does not lead to upper bounds on SUSY
breaking parameters that are strictly valid for all combinations of parameters
and of interest for existing or planned collider experiments; in particular,
gluino and squark masses in excess of 5 TeV cannot strictly be excluded. On the
other hand, in the ``generic'' case of a gaugino--like neutralino whose
annihilation cross sections are not ``accidentally'' enhanced by a nearby Higgs
or $Z$ pole, all sparticles should lie within the reach of the proposed $pp$
and $e^+e^-$ supercolliders. We also find that requiring the LSP to provide all
dark matter predicted by inflationary models imposes a strict lower bound of 40
GeV on the common scalar mass $m$ at the Planck scale, while the lightest
sleptons would have to be heavier
|
hep-ph/9207234
| 727,389 |
Decay constants of $D$ and $B$ mesons are estimated within the framework of a
heavy-quark approach using measured isospin mass splittings in the $D$, $D^*$,
and $B$ states to isolate the electromagnetic hyperfine interaction between
quarks. The values $f_D = (262 \pm 29)$ MeV and $f_B = (160 \pm 17)$ MeV are
obtained. Only experimental errors are given; possible theoretical ambiguities,
and suggestions for reducing them, are noted.
|
hep-ph/9207235
| 727,390 |
A unified treatment of both superconformal and quasisuperconformal algebras
with quadratic non-linearity is given. General formulas describing their
structure are found by solving the Jacobi identities. A complete classification
of quasisuperconformal and ${\bf Z}_2\times{\bf Z}_2$-graded algebras are
obtained and in addition to the previously known cases five exceotional
quasisuperconformal algebras and a series of ${\bf Z}_2\times{\bf
Z}_2$-superconformal algebras containing affine
$\widehat{sp}_2\otimes\widehat{osp}(N|2M)$ are constructed.
|
hep-th/9207035
| 727,391 |
We discuss the quantization of theories which are formulated using
compensating fields. In particular, we discuss the relation between the
components formulation and the superspace formulation of supergravity theories.
The requirement that the compensating field can be eliminated at the quantum
level gives rise to on-shell constraints on the operators of the theory. In
some cases, the constraints turn out to be physically unacceptable. Using these
considerations we show that new minimal supergravity is in general anomalous.
|
hep-th/9207038
| 727,392 |
The Vassiliev-Gusarov link invariants of finite type are known to be closely
related to perturbation theory for Chern-Simons theory. In order to clarify the
perturbative nature of such link invariants, we introduce an algebra V_infinity
containing elements g_i satisfying the usual braid group relations and elements
a_i satisfying g_i - g_i^{-1} = epsilon a_i, where epsilon is a formal variable
that may be regarded as measuring the failure of g_i^2 to equal 1.
Topologically, the elements a_i signify crossings. We show that a large class
of link invariants of finite type are in one-to-one correspondence with
homogeneous Markov traces on V_infinity. We sketch a possible application of
link invariants of finite type to a manifestly diffeomorphism-invariant
perturbation theory for quantum gravity in the loop representation.
|
hep-th/9207041
| 727,392 |
We study a three dimensional analogue of the Wess--Zumino--Witten model,
which describes the Goldstone bosons of three dimensional Quantum
Chromodynamics. The topologically non--trivial term of the action can also be
viewed as a nonlinear realization of Chern--Simons form. We obtain the current
algebra of this model by canonical methods. This is a three dimensional
generalization of the Kac--Moody algebra.
|
hep-th/9207039
| 727,392 |
We prove a useful identity valid for all $ADE$ minimal S-matrices, that
clarifies the transformation of the relative thermodynamic Bethe Ansatz (TBA)
from its standard form into the universal one proposed by Al.B.Zamolodchikov.
By considering the graph encoding of the system of functional equations for the
exponentials of the pseudoenergies, we show that any such system having the
same form as those for the $ADE$ TBA's, can be encoded on $A,D,E,A/Z_2$ only.
This includes, besides the known $ADE$ diagonal scattering, the set of all
$SU(2)$ related {\em magnonic} TBA's. We explore this class sistematically and
find some interesting new massive and massless RG flows. The generalization to
classes related to higher rank algebras is briefly presented and an intriguing
relation with level-rank duality is signalled.
|
hep-th/9207040
| 727,392 |
Inflation creates both scalar (density) and tensor (gravity wave) metric
perturbations. We find that the tensor mode contribution to the CMB anisotropy
on large-angular scales can only exceed that of the scalar mode in models where
the spectrum of perturbations deviates significantly from scale invariance
(e.g., extended and power-law inflation models and extreme versions of chaotic
inflation). If the tensor mode dominates at large-angular scales, then the
value of $\Delta T/T$ predicted on $1^\circ$ is less than if the scalar mode
dominates, and, for cold dark matter models, $b>1$ can be made consistent with
the COBE DMR results.
|
astro-ph/9207001
| 727,392 |
Two qualitatively different modes of ending superluminal expansion are
possible in extended inflation. One mode, different from the one envoked in
most extended models to date, easily avoids making big bubbles that distort the
cosmic microwave background radiation (CMBR). In this mode, the spectrum of
density fluctuations is found to be scale-free, $P(k) \propto k^n$, where $n$
might lie anywhere between 0.5 and 1.0 (whereas, previously, it appeared that
the range $1.0> n \gtsim 0.84$ was disallowed).
|
astro-ph/9207002
| 727,392 |
We discuss a few tightly connected problems, such as the $U(1)$ problem,
confinement, the $\theta$ -dependence within a framework of the dynamical toron
approach. We calculate two fundamental characteristics of the theory: the
vacuum expectation value (vev) of the Wilson loop and the topological
susceptibility. The analogy with well known 2+1 dimensional QED which exhibits
confinement phenomenon is also discussed.
|
hep-ph/9207238
| 727,393 |
The quantum properties of two-dimensional matter-dilaton gravity
---which includes a large family of actions for two-dimensional gravity (in
particular, string-inspired models)--- are investigated. The one-loop
divergences in linear covariant gauges are calculated and the structure of the
one-loop renormalization is studied. The explicit forms of the dilaton
potential, dilaton-Maxwell, and dilaton-scalar couplings for which the theory
is one-loop multiplicatively renormalizable are found.
A comparison with the one-loop renormalization structure of four-dimensional
gravity-matter theory is given. Charged multiple-horizon black holes which
appear in the model are also considered.
|
hep-th/9207046
| 727,393 |
Recently it has been suggested by A. M. Tsvelik that quantum S=1/2
antiferromagnet can be described by the Majorana fermions in an irreducible way
and without any constraint. In contrast to this claim we shall show that this
representation is highly reducible. It is a direct sum of four irreducible
fundamental representations of $su(2)$ algebra.
|
cond-mat/9207013
| 727,393 |
The most natural MSW neutrino oscillation interpretation of the GALLEX and
other solar neutrino data, which invokes $m_{\nu_\mu}\sim3\times10^{-3}\eV$,
and a general GUT see-saw hierarchy of neutrino masses,
$m_{\nu_{e,\mu,\tau}}\sim (m_{u,c,t})^2/M_U$, suggest that
$m_{\nu_\tau}\sim10\eV$ in agreement with the preference of COBE and other data
on large-scale structure in the Universe for a hot component in the Dark
Matter. The general see-saw model also suggests that neutrino mixing angles are
related to quark mixing angles, which is also consistent with the oscillation
interpretation of the solar neutrino data, and suggests that the forthcoming
CHORUS and NOMAD experiments at CERN have a good chance of observing $\nu_\mu -
\nu_\tau$ oscillations. We present a minimal realization of the general see-saw
hierarchy in the context of flipped $SU(5)$.
|
hep-ph/9207237
| 727,393 |
A systematic way of formulating the Batalin-Vilkovisky method of quantization
was obtained in terms of the ``odd time'' formulation. We show that in a class
of gauge theories it is possible to find an ``odd time lagrangian'' yielding,
by a Legendre transformation, an ``odd time hamiltonian'' which is the minimal
solution of the master equation. This constitutes a very simple method of
finding the minimal solution of the master equation which is usually a tedious
task. To clarify the general procedure we discussed its application to
Yang-Mills theory, massive (abelian) theory in Stueckelberg formalism,
relativistic particle and the self-interacting antisymmetric tensor field.
|
hep-th/9207052
| 727,393 |
A new quantum mechanical wave equation describing a particle with frictional
forces is derived. It depends on a parameter $\alpha$ whose range is determined
by the coefficient of friction $\gamma$, that is, $0 \leq \alpha \leq \gamma$.
For one extreme value of this parameter, $\alpha = 0$, we recover Kostin's
equation. For the other extreme value, $\alpha = \gamma$, we obtain an equation
in which friction manifests in "magnetic" type terms. It further exhibits
breakdown of translational invariance, manifesting through a symmetry breaking
parameter $\beta$, as well as localized stationary states in the absence of
external potentials. Other physical properties of this new class of equations
are also discussed.
|
hep-th/9207047
| 727,393 |
A brief review is given of an adaptation of the coadjoint orbit method
appropriate for study of models with infinite-dimensional symmetry groups. It
is illustrated on several examples, including derivation of the WZNW action of
induced $D=2\,$ $(N,0)\,$ supergravity. As a main application, we present the
geometric action on a generic coadjoint orbit of the deformed group of area
preserving diffeomorphisms. This action is precisely the anomalous effective
WZNW action of $D=2 \,$ matter fields coupled to chiral $W_\infty$ gravity
background. Similar actions are given which produce the {\em KP} hierarchy as
on-shell equations of motion.
|
hep-th/9207048
| 727,393 |
We present an in depth discussion of the production of gravitational waves
from an inflationary phase that could have occurred in the early universe,
giving derivations for the resulting spectrum and energy density. We also
consider the large-scale anisotropy in the cosmic microwave background
radiation coming from these waves. Assuming that the observed quadrupole
anisotropy comes mostly from gravitational waves (consistent with the
predictions of a flat spectrum of scalar density perturbations and the measured
dipole anisotropy) we describe in detail how to derive a value for the scale of
inflation of $(1.5-5)\times 10^{16}$GeV, which is at a particularly interesting
scale for particle physics. This upper limit corresponds to a 95\% confidence
level upper limit on the scale of inflation assuming only that the quadrupole
anisotropy from gravitational waves is not cancelled by another source. Direct
detection of gravitational waves produced by inflation near this scale will
have to wait for the next generation of detectors.
|
hep-ph/9207239
| 727,393 |
We derive the basic correlation functions of twist fields coming from
arbitrary twisted sectors in symmetric $Z_N$ orbifold conformal field theories,
keeping all the admissible marginal perturbations, in particular those
corresponding to the antisymmetric tensor background field. This allows a
thorough investigation of modular symmetries in this type of string
compactification. Such a study is explicitly carried out for the group
generated by duality transformations. Thus, apart from being of
phenomenological use, our couplings are also interesting from the mathematical
point of view as they represent automorphic functions for a large class of
discrete groups.
|
hep-th/9207049
| 727,393 |
We propose a new formulation of the heterotic $D=10$ Green-Schwarz
superstring whose worldsheet is a superspace with two even and eight odd
coordinates. The action is manifestly invariant under both target-space
supersymmetry and a worldsheet reparametrisation supergroup. It contains only a
finite set of auxiliary fields. The key ingredient are the commuting spinor
(twistor) variables, which naturally arise as worldsheet superpartners of the
target space Grassmann coordinates. These spinors parametrise the sphere $S^8$
regarded as a coset space of the $D=10$ Lorentz group. The sphere is associated
with the lightlike vector of one of the string Virasoro constraints. The origin
of the on-shell $D=10$ fermionic kappa symmetry of the standard Green-Schwarz
formulation is explained. An essential and unusual feature is the appearance of
the string tension only on shell as an integration constant.
|
hep-th/9207050
| 727,393 |
We derive an expression in closed form for the action of a finite element of
the Virasoro Group on generalized vertex operators. This complements earlier
results giving an algorithm to compute the action of a finite string of
generators of the Virasoro Algebra on generalized vertex operators. The main
new idea is to use a first order formalism to represent the infinitesimal group
element as a loop variable. To obtain a finite group element it is necessary to
thicken the loop to a band of finite thickness. This technique makes the
calculation very simple.
|
hep-th/9207051
| 727,393 |
We investigate the possibility that the difference between the measurements
of $\alpha_3(M_Z)$ from the hadronic branching ratio of the $Z^0$ and the world
average of other measurements is due to the decay of the $Z^0$ into quark,
anti-squark, and gluino. Consequences for supersymmetry breaking models are
discussed.
|
hep-ph/9207240
| 727,394 |
We report numerical simulation of the deposition of spherical particles on a
planar surface, by ballistic, straight-line trajectory transport, and assuming
irreversible adhesion on contact with the surface or previously deposited
particles. Our data indicate that the deposit formed has a loosely layered
structure within few diameters from the surface. This structure can be
explained by a model of growth via chain formation. Away from the surface we
found evidence of a monotonic, power-law approach to the bulk density. Both
density and contact-statistics results suggest that the deposit formed is
sparse: the space-filling fraction is about 15%, and the average number of
contacts is 2. The morphology of the deposit both near the surface and in the
bulk seems to be a result of competition of screening and branching; nearly
half of all the spheres are either single-contact dangling ends, or branching
nodes with more than two contacts.
|
cond-mat/9207014
| 727,394 |
We describe a method for evaluating chiral gauge theories that is not plagued
by the doubling problem. To demonstrate the efficiency of the approach, we
apply our ideas to the chiral Schwinger model.
|
hep-lat/9207012
| 727,394 |
The topological vacuum structure of the two-dimensional $~CP^{n-1}~$ model
for $~n = 3,5,7~$ is studied on the lattice. In particular we investigate the
small-volume limit on the torus as well as on the sphere and compare with
continuum results. For $~n \ge 5~$ , where lattice artifacts should be
suppressed, the topological susceptibility shows unexpectedly strong deviations
from asymptotic scaling. On the other hand there is an indication for a
convergence to values obtained analytically within the limit $~n \rightarrow
\infty~$ .
|
hep-lat/9207013
| 727,394 |
We derive an improved mean-field approximation for k-body annihilation
reactions kA --> inert, for hard-core diffusing particles on a line,
annihilating in groups of k neighbors with probability 0 < q <= 1. The hopping
and annihilation processes are correlated to mimic chemical reactions. Our new
mean-field theory accounts for hard-core particle properties and has a larger
region of applicability than the standard chemical rate equation especially for
large k values. Criteria for validity of the mean-field theory and its use in
phenomenological data fits are derived. Numerical tests are reported for
k=3,4,5,6.
|
cond-mat/9207015
| 727,394 |
The one dimensional Kondo lattice model is investigated using Quantum Monte
Carlo and transfer matrix techniques. In the strong coupling region
ferromagnetic ordering is found even at large band fillings. In the weak
coupling region the system shows an RKKY like behavior.
|
cond-mat/9207016
| 727,394 |
Gott spacetime has closed timelike curves, but no locally anomalous
stress-energy. A complete orthonormal set of eigenfunctions of the wave
operator is found in the special case of a spacetime in which the total deficit
angle is $2\pi$. A scalar quantum field theory is constructed using these
eigenfunctions. The resultant interacting quantum field theory is not unitary
because the field operators can create real, on-shell, particles in the acausal
region. These particles propagate for finite proper time accumulating an
arbitrary phase before being annihilated at the same spacetime point as that at
which they were created. As a result, the effective potential within the
acausal region is complex, and probability is not conserved. The stress tensor
of the scalar field is evaluated in the neighborhood of the Cauchy horizon; in
the case of a sufficiently small Compton wavelength of the field, the stress
tensor is regular and cannot prevent the formation of the Cauchy horizon.
|
hep-th/9207054
| 727,394 |
We discuss In\"on\"u-Wigner contractions of affine Kac-Moody algebras. We
show that the Sugawara construction for the contracted affine algebra exists
only for a fixed value of the level $k$, which is determined in terms of the
dimension of the uncontracted part of the starting Lie algebra, and the
quadratic Casimir in the adjoint representation. Further, we discuss
contractions of $G/H$ coset spaces, and obtain an affine {\it translation}
algebra, which yields a Virasoro algebra (via a GKO construction) with a
central charge given by $dim(G/H)$.
|
hep-th/9207057
| 727,394 |
We consider a soluble model of large $\phi^{4}$-graphs randomly embedded in
one compactified dimension; namely the large-order behaviour of
finite-temperature perturbation theory for the partition function of the
anharmonic oscillator. We solve the model using semi-classical methods and
demonstrate the existence of a critical temperature at which the system
undergoes a second-order phase transition from $D=1$ to $D=0$ behaviour.
Non-trivial windings of the closed loops in a graph around the compactified
time direction are interpreted as vortices. The critical point has a natural
interpretation as the temperature at which these vortices condense and disorder
the system. We show that the vortex density increases rapidly in the critical
region indicating the breakdown of the dilute vortex gas approximation at this
point. We discuss the relation of this phenomenon to the
Berezinskii-Kosterlitz-Thouless transition in the $D=1$ matrix model formulated
on a circle.
|
hep-th/9207055
| 727,394 |
We study the flux-flow Hall effect and thermomagnetic transport near the
upper critical field \hctwo\ in extreme type-II superconductors starting from a
suitable generalization of the time dependent Ginzburg-Landau equations. We
explicitly incorporate the effects of backflow into the calculations of the
local electric field and current, leading to a current which is properly
divergenceless. The Hall conductivity calculated from this current agrees with
other mean-field calculations which assume a uniform applied electric field
(the Schmid-Caroli-Maki solution), thereby vindicating these simplified
treatments. We then use these results to calculate the transverse
thermomagnetic effects (the Ettingshausen and Nernst effects). The effects of
thermal fluctuations and nonlocal elasticity of the flux lattice are
incorporated using a method recently developed by Vecris and Pelcovits [G.
Vecris and R. A. Pelcovits, Phys. Rev. B {\bf 44}, 2767 (1991)]. Our results,
taken together with those of Vecris and Pelcovits, provide a rather complete
description of the transport properties of the flux lattice state near \hctwo,
at least within the framework of time dependent Ginzburg-Landau theory.
|
cond-mat/9207017
| 727,394 |
All available data indicate a surplus of baryon states over meson states for
energies greater than about 1.5 GeV. Since hadron-scale string theory suggests
that their numbers should become equal with increasing energy, it has recently
been proposed that there must exist exotic mesons with masses just above 1.7
GeV in order to fill the deficit. We demonstrate that a string-like picture is
actually consistent with the present numbers of baryon and meson states, and in
fact predicts regular oscillations in their ratio. This suggests a different
role for new hadronic states.
|
hep-ph/9207242
| 727,394 |
Vortex motion in type II superconductors is studied starting from a variant
of the time dependent Ginzburg-Landau equations, in which the order parameter
relaxation time is taken to be complex. Using a method due to Gor'kov and
Kopnin, we derive an equation of motion for a single vortex ($B\ll H_{c2}$) in
the presence of an applied transport current. The imaginary part of the
relaxation time and the normal state Hall effect both break ``particle-hole
symmetry,'' and produce a component of the vortex velocity parallel to the
transport current, and consequently a Hall field due to the vortex motion.
Various models for the relaxation time are considered, allowing for a
comparison to some phenomenological models of vortex motion in superconductors,
such as the Bardeen-Stephen and Nozi\`eres-Vinen models, as well as to models
of vortex motion in neutral superfluids. In addition, the transport energy,
Nernst effect, and thermopower are calculated for a single vortex. Vortex
bending and fluctuations can also be included within this description,
resulting in a Langevin equation description of the vortex motion. The Langevin
equation is used to discuss the propagation of helicon waves and the
diffusional motion of a vortex line. The results are discussed in light of the
rather puzzling sign change of the Hall effect which has been observed in the
mixed state of the high temperature superconductors.
|
cond-mat/9207018
| 727,394 |
Comparison of theobservedanisotropy with that predicted iadiabaticDM models
suggest that much of thserved signal may be due to long wavelenh gravitational
waves. In inflationary models this requires the generation of tensor
fluctuations to be at least comparable to scalar density fltuations. This i is
feasible, but depends sensitively on the inflaton potential. Alternatively,
isocurvature quantum fluctuations in an axion-like field could produce a
quadrupole anisotropy proportional to the gravitational wave anisotropy,k
independent of the inflaton potential. These could also produce large scale
structure with more power on larger scales than their adiabatic counterparts.
|
hep-ph/9207243
| 727,395 |
We consider the effect of vacuum polarization around the horizon of a 4
dimensional axionic stringy black hole. In the extreme degenerate limit
($Q_a=M$), the lower limit on the black hole mass for avoiding the polarization
of the surrounding medium is $M\gg (10^{-15}\div 10^{-11})m_p$ ($m_p$ is the
proton mass), according to the assumed value of the axion mass ($m_a\simeq
(10^{-3}\div 10^{-6})~eV$). In this case, there are no upper bounds on the mass
due to the absence of the thermal radiation by the black hole. In the
nondegenerate (classically unstable) limit ($Q_a<M$), the black hole always
polarizes the surrounding vacuum, unless the effective cosmological constant of
the effective stringy action diverges.
|
hep-th/9207059
| 727,395 |
A numerical investigation of time-separated charge overlap measurements is
carried out for the pion in the context of lattice QCD using smeared Wilson
fermions. The evolution of the charge distribution function is examined and the
expected asymptotic time behavior $\sim e^{-(E_{q}-m_{\pi})t}$, where $t$
represents the charge density relative time separation, is clearly visible in
the Fourier transform. Values of the pion form factor are extracted using
point-to-smeared correlation functions and are seen to be consistent with the
expected monopole form from vector dominance. The implications of these results
for hadron structure calculations is briefly discussed.
|
hep-lat/9207014
| 727,395 |
Additional symmetries of the $p$-reduced KP hierarchy are generated by the
Lax operator $L$ and another operator $M$, satisfying $res (M^n L^{m+n/p})$ = 0
for $1 \leq n \leq p-1$ and $m \geq -1$ with the condition that ${\partial L
\over {\partial t_{kp}}}$ = 0, $k$ = 1, 2,..... We show explicitly that the
generators of these additional symmetries satisfy a closed and consistent
W-algebra only when we impose the extra condition that ${\partial M \over
{\partial t_{kp}}} = 0$.
|
hep-th/9207058
| 727,395 |
We re-examine the classification of supersymmetric extended objects in the
light of the recently discovered Type II p-branes, previously thought not to
exist for p> 1. We find new points on the brane-scan only in D = 10 and then
only for p = 3(Type IIB), p = 4 (Type IIA), p = 5 (Type IIA and IIB) and p = 6
(Type IIA). The case D = 10, p = 2 (Type IIA) also exists but is equivalent to
the previously classified D = 11 supermembrane.
|
hep-th/9207060
| 727,395 |
In this note we investigate the generalised critical $N=2$ superstrings in
$(1,2p)$ spacetime signature. We calculate the four-point functions for the
tachyon operators of these theories. In contrast to the usual $N=2$ superstring
in $(2,2)$ spacetime, the four-point functions do not vanish. The exchanged
particles of the four-point function are included in the physical spectrum of
the corresponding theory and have vanishing fermion charge.
|
hep-th/9207062
| 727,395 |
It is shown that the Affine Toda models (AT) constitute a ``gauge fixed''
version of the Conformal Affine Toda model (CAT). This result enables one to
map every solution of the AT models into an infinite number of solutions of the
corresponding CAT models, each one associated to a point of the orbit of the
conformal group. The Hirota's $\tau$-function are introduced and soliton
solutions for the AT and CAT models associated to $\hat {SL}(r+1)$ and $\hat
{SP}(r)$ are constructed.
|
hep-th/9207061
| 727,395 |
We report on a calculation of large scale anisotropy in the cosmic microwave
background radiation in the global monopole and texture models for cosmic
structure formation. We have evolved the six component linear gravitational
field along with the monopole or texture scalar fields numerically in an
expanding universe and performed the Sachs-Wolfe integrals directly on the
calculated gravitational fields. On scales $> 7^\circ$, we find a Gaussian
distribution with an approximately scale invariant fluctuation spectrum. The
$\Delta T/T$ amplitude is a factor of 4-5 larger than the prediction of the
standard CDM model with the same Hubble constant and density fluctuation
normalization. The recently reported COBE-DMR results imply that global
monopole and texture models require high bias factors or a large Hubble
constant in contrast to standard CDM which requires very low $H_0$ and bias
values. For $H_0 = 70 {\rm {km\over sec} Mpc^{-1}}$, we find that normalizing
to the COBE results implies $b_8 \simeq 3.2\pm 1.4$ (95\% c.l.). If we restrict
ourselves to the range of bias factors thought to be reasonable before the
announcement of the COBE results, $1.5 \lsim b_8 \lsim 2.5$, then it is fair to
conclude that global monopoles and textures are consistent with the COBE
results and are a {\it better} fit than Standard CDM.
|
hep-ph/9207244
| 727,395 |
A pseudo-Nambu-Goldstone boson, with a potential of the form $V(\phi) =
\Lambda^4[1 \pm \cos(\phi/f)], naturally gives rise to inflation if $f \sim
M_{Pl}$ and $\Lambda \sim M_{GUT}$. We show how this can arise in
technicolor-like and superstring models, and work out an explicit string
example in the context of multiple gaugino condensation models. We study the
cosmology of this model in detail, and find that sufficient reheating to ensure
that baryogenesis can take place requires $f > 0.3 M_{Pl}$. The primordial
density fluctuation spectrum generated is a non-scale-invariant power law,
$P(k) \propto k^{n_s}$, with $n_s \simeq 1 - (M^2_{Pl}/8\pi f^2)$, leading to
more power on large length scales than the $n_s = 1$ Harrison-Zeldovich
spectrum. The standard CDM model with $0 \la n_s \la 0.6-0.7$ could in
principle explain the large-scale clustering observed in the APM and IRAS
galaxy surveys as well as large-scale flows, but the COBE microwave anisotropy
implies such low amplitudes (or high bias factors, $b>2$) for these CDM models
that galaxy formation occurs too late to be viable; combining COBE with
sufficiently early galaxy formation or the large-scale flows leads to $n_s
>0.6$, or $f > 0.3 M_{Pl}$ as well. For extended and power law inflation
models, this constraint is even tighter, $n_s > 0.7$; combined with other
bounds on large bubbles in extended inflation, this leaves little room for most
extended models.
|
hep-ph/9207245
| 727,396 |
The braid group dynamics captures the fractional quantum Hall effect (FQHE)
as a manifestation of puncture phase. When the dynamics is generalized for
particles on a multi-sheeted surface, we obtain new tools which determine the
fractional charges, the quantum statistics, and the filling factors of the
multi-layered FQHE. A many-quasi-hole wavefunction is proposed for the
bilayered samples. We also predict a $\nu = 5/7$ FQHE for triple-layered
samples. The viability of {\em 3-dimensional} FQHE and the application of the
concept of generalized duality to anyonic superconductivity are discussed.
|
cond-mat/9207019
| 727,396 |
We show that the notion of mutual statistics arises naturally from the
representation theory of the braid group over the multi-sheeted surface. A
Hamiltonian which describes particles moving on the double-sheeted surface is
proposed as a model for the bilayered fractional quantum Hall effect (FQHE)
discovered recently. We explicitly show that the quasi-holes of the bilayered
Hall fluid display fractional mutual statistics. A model for 3-dimensional FQHE
using the multi-layered sample is suggested.
|
cond-mat/9207020
| 727,396 |
Recent theories of the NMR in the CuO superconductors are based on a
spin-singlet $d_{x^2-y^2}$ order parameter. Since this state has nodal lines on
the Fermi surface, nonlinear effects associated with low-energy quasiparticles
become important, particularly at low temperatures. We show that the
field-dependence of the supercurrent, below the nucleation field for vortices,
can be used to locate the positions of the nodal lines of an unconventional gap
in momentum space, and hence test the proposed $d_{x^2-y^2}$ state.
|
cond-mat/9207021
| 727,396 |
We consider fermion-gauge couplings in the Wilson-Yukawa approach for lattice
chiral gauge theories. At the leading order of a fermionic hopping parameter
expansion we find that the fermion-gauge coupling has a chiral and tree-like
structure. We argue that this fermion-gauge coupling remains non-zero in the
continuum limit taken in the Higgs phase. Possible fermion-scalar couplings in
this approach are considered. We also evaluate the fermion interaction with an
external gauge field in the slightly modified model and show that it has a
chiral structure in general.
|
hep-lat/9207018
| 727,397 |
We verify the Kosterlitz Thouless scenario for three different SOS
(solid-on-solid) models, including the dual transforms of XY-models with
Villain and with cosine action. The method is based on a matching of the
renormalization group (RG) flow of the candidate models with the flow of a bona
fide KT model, the exactly solvable BCSOS model. We obtain high precision
estimates for the critical couplings and other non-universal quantities.
|
hep-lat/9207019
| 727,398 |
We adapt the VMR (valleys-to-mountains reflections) algorithm, originally
devised by us for simulations of SOS models, to the BCSOS model. It is the
first time that a cluster algorithm is used for a model with constraints. The
performance of this new algorithm is studied in detail in both phases of the
model, including a finite size scaling analysis of the autocorrelations.
|
cond-mat/9207022
| 727,398 |
We present a new parametrisation of the space of solutions of the
Wess-Zumino-Witten model on a cylinder, with target space a compact, connected
Lie group G. Using the covariant canonical approach the phase space of the
theory is shown to be the co-tangent bundle of the loop group of the Lie group
G, in agreement with the result from the Hamiltonian approach. The Poisson
brackets in this phase space are derived. Other formulations in the literature
are shown to be obtained by locally-valid gauge-fixings in this phase space.
|
hep-th/9207066
| 727,399 |
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