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Alice strings are cosmic strings that turn matter into antimatter. Although
they arise naturally in many GUT's, it has long been believed that because of
the monopole problem they can have no cosmological effects. We show this
conclusion to be false; by using the Langacker-Pi mechanism, monopoles can in
fact be annihilated while Alice strings are left intact. This opens up the
possibility that they can after all contribute to cosmology, and we mention
some particularly important examples.
|
hep-ph/9204227
| 727,311 |
We reformulate the heavy quark effective theory in the presence of a residual
mass term, which has been taken to vanish in previous analyses. While such a
convention is permitted, the inclusion of a residual mass allows us to resolve
a potential ambiguity in the choice of the expansion parameter which defines
the effective theory. We show to subleading order in the mass expansion that
physical quantities computed in the effective theory do not depend on the
expansion parameter.
|
hep-ph/9204229
| 727,311 |
Let H be the corner-transfer-matrix Hamiltonian for the six-vertex model in
the anti-ferroelectric regime. It acts on the infinite tensor product W = V . V
. V ....., where is the 2-dimensional irreducible representation of the quantum
affine sl(2). We observe that H is the derivation of quantum affine sl(2), and
conjecture that the eigenvectors of H form the level-1 vacuum representation of
quantum affine sl(2). We report on checks in support of our conjecture.
|
hep-th/9204068
| 727,311 |
We study the topological nature of both isotropic and anisotropic SU(N)
Thirring model. It is shown that in the isotropic model there exists the
special point where the system lives in the topological phase and that in the
anisotropic one which is obtained by introducing two coupling constants and has
U(1) symmetry, we present a simple mechanism of the dynamical topological phase
transition which takes place at the infinite energy scale.
|
hep-th/9204073
| 727,311 |
We show in detail how the presence of a heat bath of photons effectively
gives charged particles in the final state of a decay process a
temperature-dependent mass, and changes the effective strength of the force
responsible for the decay. At low temperature, gauge invariance causes both
these effects to be largely cancelled by absorption of photons from the heat
bath and by stimulated emission into it, but at high temperature the
temperature-dependent mass is the dominant feature.
|
hep-ph/9204231
| 727,311 |
We've been studying the ``tweed'' precursors above the martensitic transition
in shape--memory alloys. These characteristic cross--hatched modulations occur
for hundreds of degrees above the first--order shape--changing transition. Our
two--dimensional model for this transition, in the limit of infinite elastic
anisotropy, can be mapped onto a spin--glass Hamiltonian in a random field. We
suggest that the tweed precursors are a direct analogy of the spin--glass
phase. The tweed is intermediate between the high--temperature cubic phase and
the low--temperature martensitic phase in the same way as the spin--glass phase
can be intermediate between ferromagnet and antiferromagnet.
|
cond-mat/9204012
| 727,311 |
The cosmology of the string effective action, including one loop string
threshold corrections, is analyzed for static compactifications. The stability
of the minima of a general supersymmetry breaking potential is studied in the
presence of radiation. In particular, it is shown that the radiation bath makes
the minima with negative cosmological constant unstable.
|
hep-th/9204079
| 727,311 |
We study the coefficients of the expansion $F(R) = 1/3 c_3 R^3 + 1/2 c_2 R^2
+ c_1 R$ of the free energy of spherical bubbles at $T=T_c$ in pure glue QCD
using lattice Monte Carlo techniques. The coefficient $c_3$ vanishes at $T=T_c$
and our results suggest that the sign and the order of magnitude of $c_1$ is in
agreement with the value $c_1=\pm 32\pi T_c^2/9$ (- for hadronic bubbles in
quark phase, + for quark bubbles in hadronic phase) computed by Mardor and
Svetitsky from the MIT bag model. The parameter $c_2$ is small in agreement
with earlier determinations.
|
hep-lat/9204013
| 727,311 |
We consider the low energy limit of three dimensional Quantum Chromodynamics
with an even number of flavors. We show that Parity is not spontaneously
broken, but the global (flavor) symmetry is spontaneously broken. The low
energy effective lagrangian is a nonlinear sigma model on the Grassmannian.
Some Chern--Simons terms are necessary in the lagrangian to realize the
discrete symmetries correctly. We consider also another parametrization of the
low energy sector which leads to a three dimensional analogue of the
Wess--Zumino--Witten--Novikov model. Since three dimensional QCD is believed to
be a model for quantum anti--ferromagnetism, our effective lagrangian can
describe their long wavelength excitations (spin waves).
|
hep-th/9204075
| 727,311 |
We show that baryons of three dimensional Quantum Chromodynamics can be
understood as solitons of its effective lagrangian. In the parity preserving
phase we study, these baryons are fermions for odd $N_c$ and bosons for even
$N_c$, never anyons. We quantize the collective variables of the solitons and
there by calculate the flavor quantum numbers, magnetic moments and mass
splittings of the baryon. The flavor quantum numbers are in agreement with
naive quark model for the low lying states. The magnetic moments and mass
splittings are smaller in the soliton model by a factor of $\log {F_\pi\over
N_c m_\pi}$. We also show that there is a dibaryon solution that is an analogue
of the deuteron. These solitons can describe defects in a quantum
anti--ferromagnet.
|
hep-th/9204076
| 727,311 |
The signatures of the inner product matrices on a Lie algebra's highest
weight representation are encoded in the representation's signature character.
We show that the signature characters of a finite-dimensional Lie algebra's
highest weight representations obey simple difference equations that have a
unique solution once appropriate boundary conditions are imposed. We use these
results to derive the signature characters of all $A_2$ and $B_2$ highest
weight representations. Our results extend, and explain, signature patterns
analogous to those observed by Friedan, Qiu and Shenker in the Virasoro
algebra's representation theory.
|
hep-th/9204077
| 727,311 |
We consider an $SU(2)_L \times SU(2)_R \times U(1)_{B-L} \times SU(3)_H^{VL}$
gauge model with natural flavour conservation in the Higgs sector, in which
CP-violation occurs due to the horizontal interactions only. We calculate the
CP-violating observables $\epsilon$ and $\epsilon'$ of the neutral kaon sector
and $d_n$, the electric dipole moment of the neutron. The regions of the
parameter space which yield a value of $\epsilon$ that is in agreement with the
experiment, lead to predictions for $\epsilon'$ and $d_n$ which are at least
five orders of magnitude smaller than the current experimental upper bounds.
|
hep-ph/9204233
| 727,311 |
We argue that the description of meson-nucleon dynamics based on the
boson-exchange approach, is compatible with the description of the nucleon as a
soliton in the nonrelativistic limit. Our arguments are based on an analysis of
the meson-soliton form factor and the exact meson-soliton and soliton-soliton
scattering amplitudes in the Sine-Gordon model.
|
hep-th/9204080
| 727,312 |
We derive a general crack propagation law for slow brittle cracking, in two
and three dimensions, using symmetry, gauge invariance, and gradient
expansions. Our derivation provides explicit justification for the ``principle
of local symmetry,'' which has been used extensively to describe two
dimensional crack growth, but goes beyond that principle to describe three
dimensional crack phenomena as well. We also find that there are new materials
properties needed to describe the growth of general cracks in three dimensions,
besides the fracture toughness and elastic constants previously used to
describe cracking.
|
cond-mat/9204013
| 727,312 |
We prove that if a non-atomic separable Banach lattice in a weak Hilbert
space, then it is lattice isomorphic to $L_2(0,1)$.
|
math/9204214
| 727,312 |
In this article we report a preliminary investigation of the large $N$ limit
of a generalized one-matrix model which represents an $O(n)$ symmetric model on
a random lattice. The model on a regular lattice is known to be critical only
for $-2\le n\le 2$. This is the situation we shall discuss also here, using
steepest descent. We first determine the critical and multicritical points,
recovering in particular results previously obtained by Kostov. We then
calculate the scaling behaviour in the critical region when the cosmological
constant is close to its critical value. Like for the multi-matrix models, all
critical points can be classified in terms of two relatively prime integers
$p,q$. In the parametrization $p=(2m+1)q \pm l$, $m,l$ integers such that
$0<l<q$, the string susceptibility exponent is found to be $\gamma_{\rm
string}=-2l/(p+q-l)$. When $l=1$ we find that all results agree with those of
the corresponding $(p,q)$ string models, otherwise they are different.\par We
finally explain how to derive the large order behaviour of the corresponding
topological expansion in the double scaling limit.
|
hep-th/9204082
| 727,312 |
Topological gravity is equivalent to physical gravity in two dimensions in a
way that is still mysterious, though by now it has been proved by Kontsevich.
In this paper it is shown that a similar relation between topological and
physical Yang-Mills theory holds in two dimensions; in this case, however, the
relation can be explained by a direct mapping between the two path integrals.
This (1) explains many strange facts about two dimensional Yang-Mills theory,
like the way the partition function can be expressed exactly as a sum over
classical solutions, including unstable ones; (2) makes the corresponding
topological theory completely computable.
|
hep-th/9204083
| 727,312 |
We consider the S-matrix of c=1 Liouville theory with vanishing cosmological
constant. We examine some of the constraints imposed by unitarity. These
completely determine (N,2) amplitudes at tree level in terms of the (N,1)
amplitudes when the plus tachyon momenta take generic values. A surprising
feature of the matrix model results is the lack of particle creation branch
cuts in the higher genus amplitudes. In fact, we show the naive field theory
limit of Liouville theory would predict such branch cuts. However, unitarity in
the full string theory ensures that such cuts do not appear in genus one (N,1)
amplitudes. We conclude with some comments about the genus one (N,2)
amplitudes.
|
hep-th/9204084
| 727,312 |
The four observables associated with gravitational lensing of distant quasars
by intervening galaxies: image splittings, relative amplifications, time
delays, and optical depths, provide separate measures of the strength of the
gravitational constant $G$ at cosmological distances. These allow one, in
principle, to factor out unknown lensing parameters to directly to probe the
variation of $G$ over cosmological time. We estimate constraints on $\dot{G}$
which may be derivable by this method both now and in the future. The limits
one may obtain can compete or exceed other direct limits on $\dot{G}$ today,
but unfortunately extracting this information, is not independent of the effort
to fix other cosmological parameters such as $H_0$ and $\Omega_0$ from lensing
observations.
|
astro-ph/9204002
| 727,314 |
The multigrid methodology is reviewed. By integrating numerical processes at
all scales of a problem, it seeks to perform various computational tasks at a
cost that rises as slowly as possible as a function of $n$, the number of
degrees of freedom in the problem. Current and potential benefits for lattice
field computations are outlined. They include: $O(n)$ solution of Dirac
equations; just $O(1)$ operations in updating the solution (upon any local
change of data, including the gauge field); similar efficiency in gauge fixing
and updating; $O(1)$ operations in updating the inverse matrix and in
calculating the change in the logarithm of its determinant; $O(n)$ operations
per producing each independent configuration in statistical simulations
(eliminating CSD), and, more important, effectively just $O(1)$ operations per
each independent measurement (eliminating the volume factor as well). These
potential capabilities have been demonstrated on simple model problems.
Extensions to real life are explored.
|
hep-lat/9204014
| 727,315 |
Field-theoretic models for fields taking values in quantum groups are
investigated. First we consider $SU_q(2)$ $\sigma$ model ($q$ real) expressed
in terms of basic notions of noncommutative differential geometry. We discuss
the case in which the $\sigma$ models fields are represented as products of
conventional $\sigma$ fields and of the coordinate-independent algebra. An
explicit example is provided by the $U_q(2)$ $\sigma$ model with $q\sp{N}=1$,
in which case quantum matrices $U_q(2)$ are realised as $2N\times 2N$ unitary
matrices. Open problems are pointed out.
|
hep-th/9204086
| 727,315 |
About twenty years ago Johnson and Zippin showed that every separable
L_1(mu)-predual was isometric to a quotient of C(Delta ), where Delta is the
Cantor set. In this note we will show that the natural analogue of the theorem
for l_1-preduals does not hold. We will show that there are many l_1-preduals
which are not isometric to a quotient of any C(K)-space with K a countable
compact metric space. We also prove some general results about the relationship
between l_1-preduals and quotients of C(K)-spaces with K a countable compact
metric space.
The results in this paper were presented at the Workshop on Banach Space
Theory in Merida, Venezuela, January 1992.
|
math/9204215
| 727,315 |
Using stopping time arguments on holomorphic martingales we present a soft
way of constructing J. Bourgain's analytic partitions of unity. Applications to
Marcinkiewicz interploation in weighted Hardy spaces are discussed.
|
math/9204216
| 727,315 |
We compute the threshold uncertainties due to unknown masses of the Higgs
bosons on the predictions for the intermediate and unification scales, $M_I$
and $M_U$ respectively in SO(10) models.We focus on models with separate
breaking scales for Parity and $SU(2)_R$ symmetries since they provide a
natural realization of the see-saw mechanism for neutrino masses. For the two
step symmetry breaking chains ,where left-right symmetric gauge groups appear
at the intermediate scale, we find that parity invariance of the theory at the
unification scale drastically reduces the GUT threshold effects in some cases.
Including the effects of the intermediate scale thresholds ,we compute the
uncertainty in the above mass scales and study their implications for proton
lifetime and neutrino masses. An important outcome of our analysis is that if
the currently favored nonadiabatic MSW solution to the solar neutrino puzzle is
accepted , it will rule out the $SU(2)_LXSU(2)_RXU(1)_{B-L}X SU(3)_c$ as an
intermediate symmetry for SO(10) breaking whereas the intermediate symmetry
$SU(2)_LXSU(2)_RXSU(4)_c$, is quite consistent with it.
|
hep-ph/9204234
| 727,315 |
Starting from a covariant and background independent definition of normal
ordered vertex operators we give an alternative derivation of the KPZ relation
between conformal dimensions and their gravitational dressed partners. With our
method we are able to study for arbitrary genus the dependence of N-point
functions on all dimensionful parameters. Implications for the interpretation
of gravitational dressed dimensions are discussed.
|
hep-th/9204088
| 727,316 |
The phase transition of the electroweak vacuum induced by a strong magnetic
field is examined, and a connection is made with the Ginzburg-Landau theory of
type-II superconductivity. For solutions of the exact nonlinear field equations
of the electroweak theory with lattice periodicity in directions perpendicular
to the magnetic field, it is proven that, likewise, each lattice cell must
enclose an integer number of quanta of magnetic flux. Close to the lower
critical magnetic field, a perturbative method developed by MacDowell and the
author is used to study properties of the lattice solutions. Analytical
expressions for observables are obtained in terms of a complex parameter $\tau$
specifying the lattice and it is shown that the triangular Abrikosov solution
constitutes a local minimum of the energy provided $M_H > M_Z$.
PACS numbers: 11.15.Kc, 11.15.Ex, 74.60.-w, 05.70.Fh
|
hep-ph/9204235
| 727,316 |
Cluster algorithms are developed for simulating quantum spin systems like the
one- and two-dimensional Heisenberg ferro- and anti-ferromagnets. The
corresponding two- and three-dimensional classical spin models with four-spin
couplings are maped to blockspin models with two-blockspin interactions.
Clusters of blockspins are updated collectively. The efficiency of the method
is investigated in detail for one-dimensional spin chains. Then in most cases
the new algorithms solve the problems of slowing down from which standard
algorithms are suffering.
|
cond-mat/9204014
| 727,316 |
Cluster algorithms are developed for simulating quantum spin systems like the
one- and two-dimensional Heisenberg ferro- and anti-ferromagnets. The
corresponding two- and three-dimensional classical spin models with four-spin
couplings are maped to blockspin models with two-blockspin interactions.
Clusters of blockspins are updated collectively. The efficiency of the method
is investigated in detail for one-dimensional spin chains. Then in most cases
the new algorithms solve the problems of slowing down from which standard
algorithms are suffering.
|
hep-lat/9204015
| 727,316 |
Paragrassmann algebras with one and many paragrassmann variables are
considered from the algebraic point of view without using the Green ansatz.
Operators of differentiation with respect to paragrassmann variables and a
covariant para-super-derivative are introduced giving a natural generalization
of the Grassmann calculus to a paragrassmann one. Deep relations between
paragrassmann algebras and quantum groups with deformation parameters being
roots of unity are established.
|
hep-th/9204089
| 727,316 |
We examine the two-dimensional spacetimes that emerge from string theory. We
find all the solutions with no tachyons, and show that the only non-trivial
solution is the black hole spacetime. We examine the role of duality in this
picture. We then explore the thermodynamics of these solutions which is
complicated by the fact that only in two spacetime dimensions is it impossible
to redefine the dilaton field in terms of a canonical scalar field. Finally, we
extend our analysis to the heterotic string, and briefly comment on exact, as
opposed to perturbative, solutions.
|
hep-th/9204090
| 727,316 |
It is known that in systems which contain randomness explicitly in their
Hamiltonians (e.g., due to impurities), the characteristic size L of the
ordered domains can grow only logarithmically with time t following a quench
below the transition temperature. However, in systems without such imposed
randomness, much faster power law growth has generally been predicted.
Motivated by the slow dynamics present in glasses, we have been looking for
counterexamples, i.e., for models without randomness which nonetheless order
logarithmically slowly. Here, we discuss two closely related models for which
we have simple physical arguments that such slow growth occurs. The basis of
these arguments is the claim that the free energy barriers to domain growth in
these models are proportional to L. Thus, the barriers grow as the domains
coarsen. We present the results of Monte Carlo simulations, which lend strong
support to our claims of growing barriers and logarithmically slow dynamics.
Finally, we discuss how quickly the system orders when it is cooled
continuously through the transition (rather than quenched).
|
cond-mat/9204015
| 727,316 |
A new set of realizations of the Virasoro algebra on a bosonic Fock space are
found by explicitly computing the Virasoro representations associated with
coadjoint orbits of the form (Diff S1) / S1. Some progress is made in
understanding the unitary structure of these representations. The characters of
these representations are exactly the bosonic partition functions calculated
previously by Witten using perturbative and fixed-point methods. The
representations corresponding to the discrete series of unitary Virasoro
representations with c <= 1 are found to be reducible in this formulation,
confirming a conjecture by Aldaya and Navarro-Salas.
|
hep-th/9204091
| 727,316 |
It is well-known that solutions to the string equation are generated by
elements of Sato's Grassmannian which are invariant under action of some
differential operator. Here it is shown that this operator is nothing else than
the infinitesimal operator of the group of additional symmetries of the KdV
flow. This is done for KdV hierarchies of arbitrary orders. Virasoro
constraints are obtained in a slightly more general form than they are usually
written.
|
hep-th/9204092
| 727,316 |
We review some of the recent developments in the construction of $W$-string
theories. These are generalisations of ordinary strings in which the
two-dimensional ``worldsheet'' theory, instead of being a gauging of the
Virasoro algebra, is a gauging of a higher-spin extension of the Virasoro
algebra---a $W$ algebra. Despite the complexity of the (non-linear) $W$
algebras, it turns out that the spectrum can be computed completely and
explicitly for more or less any $W$ string. The result is equivalent to a set
of spectra for Virasoro strings with unusual central charge and intercepts.
|
hep-th/9204093
| 727,316 |
Here, we summarize the most important results of our study of logarithmically
slow growth of domains following a quench in two models without randomness in
their Hamiltonians.
This is a slightly updated version of a paper to appear in the Proceedings of
the 1st Annual Tohwa University International Symposium, Fukuoka, Japan
(American Institute of Physics, 1992). It is meant to serve as a brief summary
of cond-mat/9204015 for those who do not wish to read all the details contained
therein (and don't want to hassle with 2 MBytes of tex/ps files).
|
cond-mat/9204016
| 727,316 |
A one-dimensional quantum N-body system of either fermions or bosons with
$SU(n)$ colors interacting via inverse-square exchange is presented in this
article. A class of eigenstates of both the continuum and lattice version of
the model Hamiltonians is constructed in terms of the Jastrow-product type wave
function. The class of states we construct in this paper corresponds to the
ground state and the low energy excitations of the model that can be described
by the effective harmonic fluid Hamiltonian. By expanding the energy about the
ground state we find the harmonic fluid parameters (i.e. the charge, spin
velocities, etc.), explicitly. The correlation exponent and the compressibility
of are also found. As expected the general harmonic relation(i.e.
$v_S=(v_Nv_J)^{1/2}$) is satisfied among the charge and spin velocities.
|
cond-mat/9204017
| 727,317 |
We discuss in this paper various aspects of the off-critical $O(n)$ model in
two dimensions. We find the ground-state energy conjectured by Zamolodchikov
for the unitary minimal models, and extend the result to some non-unitary
minimal cases. We apply our results to the discussion of scaling functions for
polymers on a cylinder. We show, using the underlying N=2 supersymmetry, that
the scaling function for one non-contractible polymer loop around the cylinder
is simply related to the solution of the Painleve III differential equation. We
also find the ground-state energy for a single polymer on the cylinder. We
check these results by numerically simulating the polymer system. We also
analyze numerically the flow to the dense polymer phase. We find there
surprising results, with a $c_{\hbox{eff}}$ function that is not monotonous and
seems to have a roaming behavior, getting very close to the values 81/70 and
7/10 between its UV and IR values of 1.
|
hep-th/9204094
| 727,317 |
We argue that the infinitely many gauge symmetries of string theory provide
an infinite set of conserved (gauge) quantum numbers (W-hair) which
characterise black hole states and maintain quantum coherence, even during
exotic processes like black hole evaporation/decay. We study ways of measuring
the W-hair of spherically-symmetric four-dimensional objects with event
horizons, treated as effectively two-dimensional string black holes.
Measurements can be done either through the s-wave scattering of light
particles off the string black-hole background, or through interference
experiments of Aharonov-Bohm type. We also speculate on the role of the
extended W-symmetries possessed by the topological field theories that describe
the region of space-time around a singularity.
|
hep-th/9204096
| 727,317 |
The dynamics of {\it light} fermions propagating in a spatial direction at
high temperatures can be described effectively by a two--dimensional
Schr\"odinger equation with {\it heavy} effective mass $m_{\rm eff} = \pi T$.
Starting from QED, we discuss the transition from three-- to two--dimensional
positronium discussing the latter in detail including relativistic effects. In
the case of QCD the problem is similar to that of heavy quarkonium. Our
effective potential contains the usual Coulomb and confining parts as well as a
perturbative spin--spin interaction. The resulting $\bar q q$ ``wave functions"
reproduce recent lattice data for the $\rho$ and $\pi$ channels. The physical
meaning of such `confinement' is related to the non--trivial magnetic
interaction of color currents in the quark--gluon plasma. Our results do not
contradict the idea that the normal electric interaction of color charges is
screened and produces no bound states in the usual sense.
|
hep-ph/9204236
| 727,317 |
First order power corrections to current matrix elements between heavy meson
or $\Lambda_\Q$ baryon states are shown to vanish at the zero recoil point to
all orders in QCD. Five relations among the six form factors that parametrize
the semileptonic decay $\Lambda_b \to \Lambda_c e \overline{\nu}$ are also
demonstrated to exist to all orders in the strong coupling at order $1/\mQ$ .
The $O(\bas(m_c)/m_c)$ form factor relations are displayed.
|
hep-ph/9204237
| 727,317 |
Perturbative analyses seem to suggest that fermions whose mass comes solely
from a Yukawa coupling to a scalar field can be made arbitrarily heavy, while
the scalar remains light. The effects of the fermion can be summarized by a
local effective Lagrangian for the light degrees of freedom. Using weak
coupling and large N techniques, we present a variety of models in which this
conclusion is shown to be false when nonperturbative variations of the scalar
field are considered. The heavy fermions contribute nonlocal terms to the
effective action for light degrees of freedom. This resolves paradoxes about
anomalous and nonanomalous symmetry violation in these models. Application of
these results to lattice gauge theory imply that attempts to decouple lattice
fermion doubles by the method of Swift and Smit cannot succeed, a result
already suggested by lattice calculations.
|
hep-lat/9204017
| 727,317 |
We give expressions for the singular vectors in the highest weight
representations of the Virasoro algebra. We verify that the expressions ---
which take the form of a product of operators applied to the highest weight
vector --- do indeed define singular vectors. These results explain the
patterns of embeddings amongst Virasoro algebra highest weight representations.
|
hep-th/9204097
| 727,317 |
We use recently derived explicit formulae for the Virasoro algebra's singular
vectors to give constructive proofs of three results due to Feigin and Fuchs.
The main result, which is needed for a rigorous treatment of fusion, describes
the action of the singular vectors on conformal fields.
|
hep-th/9204098
| 727,317 |
We obtain lattice models whose continuum limits correspond to $N=2$
superconformal coset models. This is done by taking the well known vertex model
whose continuum limit is the $G \times G/G$ conformal field theory, and
twisting the transfer matrix and modifying the quantum group truncation. We
find that the natural order parameters of the new models are precisely the
chiral primary fields. The integrable perturbations of the conformal field
theory limit also have natural counterparts in the lattice formulation, and
these can be incorporated into an affine quantum group structure. The
topological, twisted $N=2$ superconformal models also have lattice analogues,
and these emerge as an intermediate part of our analysis.
|
hep-th/9204100
| 727,317 |
Semileptonic decay of the $B_c$ meson is studied in the heavy quark limit.
The six possible form factors for $B_c \rightarrow B_s (B^0),B_s^* (B^{*0})$
semileptonic decay are determined by two invariant functions. Only one of these
functions contributes at zero recoil, where it is calculable to lowest order in
an operator product expansion in terms of the meson decay constant $f_B$ and
the $B_c$ wavefunction. A similar result is found for $B_c \rightarrow
D^0,D^{*0}$ and for $B_c\rightarrow\eta_c,J/\psi$ semileptonic decay for a
restricted kinematic region. Semileptonic $B_c$ decay provides a means for
determining the KM mixing angle $|V_{ub}|$.
|
hep-ph/9204238
| 727,318 |
An approximation formula is derived for acceptance rates of nonlocal
Metropolis updates in simulations of lattice field theories. The predictions of
the formula agree quite well with Monte Carlo simulations of 2-dimensional Sine
Gordon, XY and phi**4 models. The results are consistent with the following
rule: For a critical model with a fundamental Hamiltonian H(phi) sufficiently
high acceptance rates for a complete elimination of critical slowing down can
only be expected if the expansion of < H(phi+psi) > in terms of the shift psi
contains no relevant term (mass term).
|
hep-lat/9204016
| 727,318 |
The response of a single vortex to a time dependent field is examined
microscopically and an equation of motion for vortex motion at non-zero
frequencies is derived. Of interest are frequencies near $\Delta^{2}/E_{F}$,
where $\Delta$ is the bulk energy gap and $E_{F}$ is the fermi energy. The low
temperature, clean, extreme type II limit and maintaining of equilibrium with
the lattice are assumed. A simplification occurs for large planar mass
anisotropy. Thus the results may be pertinent to materials such as $NbSe_2$ and
high temperature superconductors. The expected dipole transition between core
states is hidden because of the self consistent nature of the vortex potential.
Instead the vortex itself moves and has a resonance at the frequency of the
transition.
|
cond-mat/9204018
| 727,318 |
We consider here a generalization of the Abelian Higgs model in curved space,
by adding a Chern--Simons term. The static equations are self-dual provided we
choose a suitable potential. The solutions give a self-dual
Maxwell--Chern--Simons soliton that possesses a mass and a spin.
|
hep-th/9204101
| 727,318 |
A soft photon approximation is used to calculate the rates of lepton pair
production through virtual bremsstrahlung from both pions and quarks. Standard
assumptions about the evolution of a nuclear system under collision allow pion
and quark driven total production to be calculated. Comparisons are made with
Dalitz decay of light mesons. These mechanisms are expected to be significant
contributors to the soft dilepton mass spectra one might observe in heavy ion
collisions at RHIC and LHC energies.
|
hep-ph/9204239
| 727,318 |
We have calculated gamma-ray radiative transport in regions of high energy
density, such as gamma-ray burst source regions, using a discrete ordinate,
discrete energy group method. The calculations include two-photon pair
production and annihilation, as well as three-photon pair annihilation. The
radiation field itself acts as an absorbing medium, and the optical depth
depends on its intensity, so the problem is intrinsically nonlinear. Spherical
divergence produces effective collimation of the flux. At high optical depth
the high energy ($E > 1$ MeV) portion of the emergent spectrum assumes a nearly
universal form. An approximate limit is derived for the high energy flux from a
gamma-ray burst source region of given size, and the implications of this limit
for the distance to the March 5, 1979 event are briefly discussed. We discuss
more generally the problem of very luminous bursts, and implications of
Galactic halo distances for flare models.
|
astro-ph/9204005
| 727,318 |
We use the Expanding Photosphere Method to determine distances to 10 type II
supernovae. The effects of asymmetries, extinction, and flux dilution are
explored. Using empirical evidence and time-independent, spherical models which
treat H and He in non-LTE, we show that blackbody corrections caused by flux
dilution are small for type II supernovae in the infrared, and in the optical
when their color temperatures are less than 6000~K. The extinction to a type
II-P supernova can be estimated from its light curve: the uncertainty
introduced into a distance measurement due to extinction is usually less than
10\%. Correcting for extinction and flux dilution we derive distances to 10
supernovae: SN 1968L, SN 1969L, SN 1970G, SN 1973R, SN 1979C, SN 1980K, SN
1987A, SN 1988A, SN 1990E, and SN 1990ae. The distance measurements span a wide
range, 50 kpc to 120 Mpc, which is unique among the methods for establishing
the extragalactic distance scale. The distances measured to SN 1970G in M101
and SN 1987A in the LMC are in good agreement with distances determined from
Cepheid variable stars. Our distance to the Virgo Cluster, 22 +- 3 Mpc, is
larger than recent distances estimates made using surface brightness
fluctuations, planetary nebula luminosity functions, and the Tully-Fisher
method. Using the distances determined from these type II supernovae we derive
a value of $H_0 = 60 \pm 10$ km sec$^{-1}$Mpc$^{-1}$. This value is subject to
errors caused by local deviations in the Hubble flow, but will soon be improved
by applying the Expanding Photosphere Method to several distant type II
supernovae.
|
astro-ph/9204004
| 727,318 |
Dust is observed to form in nova ejecta. The grain temperature is determined
by the diluted nova radiation field rather than the gas kinetic temperature,
making classical nucleation theory inapplicable. We used kinetic equations to
calculate the growth of carbon nuclei in these ejecta. For expected values of
the parameters too many clusters grew, despite the small sticking probability
of atoms to small clusters, and the clusters only reached radii of about
100\AA\ when the carbon vapor was depleted. We then included the effects of
cluster photodissociation by ultraviolet radiation from the nova. This
suppresses nucleation, but too well, and no grains form at all. Finally we
suggest that a few growing carbon nuclei may be protected from
photodissociation by a sacrificial surface layer of hydrogen.
|
astro-ph/9204006
| 727,318 |
We show that ${\rm Tr}(-1)^F F e^{-\beta H}$ is an index for $N$=2
supersymmetric theories in two dimensions, in the sense that it is independent
of almost all deformations of the theory. This index is related to the geometry
of the vacua (Berry's curvature) and satisfies an exact differential equation
as a function of $\beta$. For integrable theories we can also compute the index
thermodynamically, using the exact $S$-matrix. The equivalence of these two
results implies a highly non-trivial equivalence of a set of coupled integral
equations with these differential equations, among them Painleve III and the
affine Toda equations.
|
hep-th/9204102
| 727,318 |
We summarize results on the reliability of the eikonal approximation in
obtaining the high energy behavior of a two particle forward scattering
amplitude. Reliability depends on the spin of the exchanged field. For scalar
fields the eikonal fails at eighth order in perturbation theory, when it misses
the leading behavior of the exchange-type diagrams. In a vector theory the
eikonal gets the exchange diagrams correctly, but fails by ignoring certain
non-exchange graphs which dominate the asymptotic behavior of the full
amplitude. For spin--2 tensor fields the eikonal captures the leading behavior
of each order in perturbation theory, but the sum of eikonal terms is
subdominant to graphs neglected by the approximation. We also comment on the
eikonal for Yang-Mills vector exchange, where the additional complexities of
the non-abelian theory may be absorbed into Regge-type modifications of the
gauge boson propagators.
|
hep-th/9204103
| 727,318 |
When the second uniform indiscernible is $\aleph_{2}$, the Martin-Solovay
tree only constructs countably many reals; this resolves a number of open
questions in descriptive set theory.
|
math/9205201
| 727,319 |
The author advocates two specific mathematical notations from his popular
course and joint textbook, "Concrete Mathematics". The first of these,
extending an idea of Iverson, is the notation "[P]" for the function which is 1
when the Boolean condition P is true and 0 otherwise. This notation can
encourage and clarify the use of characteristic functions and Kronecker deltas
in sums and integrals.
The second notation puts Stirling numbers on the same footing as binomial
coefficients. Since binomial coefficients are written on two lines in
parentheses and read "n choose k", Stirling numbers of the first kind should be
written on two lines in brackets and read "n cycle k", while Stirling numbers
of the second kind should be written in braces and read "n subset k". (I might
say "n partition k".) The written form was first suggested by Imanuel Marx. The
virtues of this notation are that Stirling partition numbers frequently appear
in combinatorics, and that it more clearly presents functional relations
similar to those satisfied by binomial coefficients.
|
math/9205211
| 727,319 |
The CP^3 spin model is simulated at large correlation lengths in two
dimensions. An overrelaxation algorithm is employed which yields reduced
critical slowing down with dynamical exponents z around unity. We compare our
results with recent multigrid data on the massgap m and the spin susceptibility
and confirm the absence of asymptotic scaling. As a new result we find scaling
for the universal topological susceptibility with values extrapolating to chi_t
/ m^2 = 0.156(2) in the continuum limit.
|
hep-lat/9205001
| 727,319 |
Discussions are made on the structures of chirally invariant lattice actions
without any restriction of hermiticity. With the help of the Ward-Takahashi
identity a general conclusion can be derived that there must be species
doublers in any chirally invariant model provided that the model is chosen as
well-regularized, that is, there is no singularity in the propagator after
introducing fermion mass on the lattice. Various examples are discussed to pick
up better models defined in the sense that the number of species doubler is
smaller than that of the naive Dirac action.
|
hep-lat/9205002
| 727,319 |
The Coulomb contribution to the temperature-dependent rate of momentum
transfer, $1/\tau_D$, between two electron systems in parallel layers is
determined by setting up two coupled Boltzmann equations, with the boundary
condition that no current flows in the layer where an induced voltage is
measured. The effective Coulomb interaction between the layers is determined
selfconsistently, allowing for the finite thickness of the layers. As
$T\rightarrow 0$, we find that $1/\tau_DT^2$ approaches a constant value. At
higher temperatures $1/\tau_DT^2$ exhibits a maximum at $T=T_{\rm max}$ and
then decreases as $1/T$ with increasing temperature. The value of $T_{\rm max}$
depends on the layer separation $d$ according to $T_{\rm max}\propto
d^{-\alpha}$, where $\alpha\simeq 0.8$. The overall magnitude of the calculated
$1/\tau_D$ is approximately one half of the results of a recent experiment,
suggesting that other mechanisms of momentum transfer may be important.
|
cond-mat/9205001
| 727,319 |
We analyze the properties of the q-vertex operators of U_q(sl(2)^) introduced
by Frenkel and Reshetikhin. As the condition for the null vector decoupling, we
derive the existence condition of the q-vertex operators ( the fusion rules ).
|
hep-th/9205002
| 727,319 |
The expressions for the $\hat{R}$--matrices for the quantum groups
SO$_{q^2}$(5) and SO$_q$(6) in terms of the $\hat{R}$--matrices for Sp$_q$(2)
and SL$_q$(4) are found, and the local isomorphisms of the corresponding
quantum groups are established.
|
hep-th/9205001
| 727,319 |
We consider a model of a reconstructed crystal surface, first considered by
Villain and Vilfan (Europhys. Lett. 12, p. 523 (1990) and Surf. Sci. 257, p.
368 (1991)) for the gold (110) surface, in which roughening occurs via the
formation of anisotropic steps traversing the entire length of the crystal. The
model is studied by a mapping to a spin--1/2 Fermion system in 1+1 dimensions,
which, in the absence of islands, is precisely the Hubbard model. We consider a
general $\pbyo$ reconstruction, in the presence of inter--step interactions and
closed islands. Our analysis predicts the existence of a new type of rough
phase, with incommensurate correlations in the reconstruction order parameter
and unusual momentum space singularities at a characteristic ``Fermi momentum''
and its harmonics, analagous to the Luttinger liquid of one--dimensional
Fermions. The general phase structure for $p>1$ is as follows: for $p>2$, there
is a flat ordered (FO), a rough incommensurate (RI), and a flat incommensurate
phase (FI). The FO--RI and FO--FI transitions are of the commensurate to
incommensurate type, and the FI--RI transition is in the Kosterlitz--Thouless
(KT) universality class. For $p=2$, the FI phase is replaced by a flat
disordered phase (FD), and there may be a new rough disordered phase (RD). The
FO--FD transition is now of Ising type, and the FD--RD and RI--RD transitions
are in the KT universality class.
|
cond-mat/9205002
| 727,319 |
We apply Perlick's (1990a) rigorous formulation of the Fermat principle in
arbitrary spacetimes to prove the correctness of the description of
gravitational lensing by gravitational waves, given in the literature using the
scalar and vector formalisms. We obtain an expression for the time delay due to
such nonstationary lenses; the advantage over previous papers is that Perlick's
formulation of the Fermat principle is very rigorous and more suitable for
practical calculations in some cases. It is also shown that ordinary moving
gravitational lenses must be considered as a stationary case.
|
astro-ph/9205001
| 727,319 |
This is a slightly extended version of the talk delivered at the Topical
Workshop ``Non perturbative aspects of chiral gauge theories'', Accademia
Nazionale dei Lincei, Roma, 9-11 March, 1992. Abstract: The Higgs mass in the
minimal standard model is bounded by triviality and vacuum stability in the
range 50--100 $GeV$ to 700--900 $GeV$. Recent results will be presented in
brief and directions for future work will be proposed.
|
hep-lat/9205003
| 727,319 |
The nonlinear reality structure of the derivatives and the differentials for
the euclidean q-spaces are found. A real Laplacian is constructed and reality
properties of the exterior derivative are given.
|
hep-th/9205003
| 727,319 |
The effect of the magnetic skew on the Parker instability is investigated by
means of the linear stability analysis for a gravitationally stratified gas
layer permeated by a horizontal magnetic field. When the magnetic field is
skewed (i.e., the field line direction is a function of the height), the
wavelength of the most unstable mode is $ \lambda \; \sim \; 10 H $ where $ H $
is the pressure scale height. The growth rate of the short wavelength modes is
greatly reduced when the gradient in the magnetic field direction exceeds 0.5
radian per scale height. Our results indicate that the Parker instability in a
skewed magnetic field preferentially forms large scale structures like giant
molecular clouds.
|
astro-ph/9205002
| 727,320 |
We use a recent classification of non-degenerate quasihomogeneous polynomials
to construct all Landau-Ginzburg (LG) potentials for N=2 superconformal field
theories with c=9 and calculate the corresponding Hodge numbers. Surprisingly,
the resulting spectra are less symmetric than the existing incomplete results.
It turns out that models belonging to the large class for which an explicit
construction of a mirror model as an orbifold is known show remarkable mirror
symmetry. On the other hand, half of the remaining 15\% of all models have no
mirror partners. This lack of mirror symmetry may point beyond the class of
LG-orbifolds.
|
hep-th/9205004
| 727,320 |
We study by numerical simulation a lattice Yukawa model with naive fermions
at intermediate values of the Yukawa coupling $y$ when the nearest neighbour
coupling $\kp$ of the scalar field $\Phi$ is very weakly ferromagnetic ($\kp
\approx 0$) or even antiferromagnetic ($\kappa < 0$) and the nonvanishing value
of $\vev$ is generated by the Yukawa interaction. The renormalized Yukawa
coupling $y_R$ achieves here its maximal value and this $y$-region is thus of
particular importance for lattice investigations of strong Yukawa interaction.
However, here the scalar field propagators have a very complex structure caused
by fermion loop corrections and by the proximity of phases with
antiferromagnetic properties. We develop methods for analyzing these
propagators and for extracting the physical observables. We find that going
into the negative $\kp$ region, the scalar field renormalization constant
becomes small and $y_R$ does not seem to exceed the unitarity bound, making the
existence of a nontrivial fixed point in the investigated Yukawa model quite
unlikely.
|
hep-lat/9205004
| 727,321 |
We propose a bilinear sampling algorithm in Green's function Monte Carlo for
expectation values of operators that do not commute with the Hamiltonian and
for differences between eigenvalues of different Hamiltonians. The integral
representations of the Schroedinger equations are transformed into two
equations whose solution has the form $\psi_a(x) t(x,y) \psi_b(y)$, where
$\psi_a$ and $\psi_b$ are the wavefunctions for the two related systems and
$t(x,y)$ is a kernel chosen to couple $x$ and $y$. The Monte Carlo process,
with random walkers on the enlarged configuration space $x \otimes y$, solves
these equations by generating densities whose asymptotic form is the above
bilinear distribution. With such a distribution, exact Monte Carlo estimators
can be obtained for the expectation values of quantum operators and for energy
differences. We present results of these methods applied to several test
problems, including a model integral equation, and the hydrogen atom.
|
cond-mat/9205003
| 727,321 |
It is shown how to construct, given a Banach space which does not have the
approximation property, another Banach space which does not have the
approximation property but which does have the compact approximation property.
|
math/9205203
| 727,322 |
I present a model for acceleration of protons by the second-order Fermi
process acting on randomly scrambled magnetic flux arches above an accretion
disc. The accelerated protons collide with thermal protons in the disc,
producing degraded energetic protons, charged and neutral pions, and neutrons.
The pions produce gamma-rays by spontaneous decay of $\pi^0$ and by
bremsstrahlung and Compton processes following the decay of $\pi^\pm$ to
$e^\pm$.
|
astro-ph/9205003
| 727,322 |
We study a class of Monte Carlo algorithms for the nonlinear $\sigma$-model,
based on a Wolff-type embedding of Ising spins into the target manifold $M$. We
argue heuristically that, at least for an asymptotically free model, such an
algorithm can have dynamic critical exponent $z \ll 2$ only if the embedding is
based on an (involutive) isometry of $M$ whose fixed-point manifold has
codimension 1. Such an isometry exists only if the manifold is a discrete
quotient of a product of spheres. Numerical simulations of the idealized
codimension-2 algorithm for the two-dimensional $O(4)$-symmetric $\sigma$-model
yield $z_{int,{\cal M}^2} = 1.5 \pm 0.5$ (subjective 68\% confidence interval),
in agreement with our heuristic argument.
|
hep-lat/9205005
| 727,322 |
We present cross sections for the production of the lightest supersymmetric
particle as a neutralino state in the minimal supersymmetric standard model at
electron-photon colliders. The lightest supersymmetric particle mass is taken
at a value of 30 GeV which is slightly higher than its lowest experimental
bound of 20 GeV, and the masses of the scalar electron are varied. We show
partial cross sections of the energy and angular distribution of the outgoing
electron for different values of the centre of mass energy. As a result we show
that electron-photon collider experiments could be quite sensitive to the
detection of supersymmetric particles.
|
hep-ph/9205201
| 727,322 |
We suggest here that CP is a discrete {\it gauge} symmetry, and is therefore
not violated by quantum gravity. We show that four dimensional CP can arise as
a discrete gauge symmetry in theories with dimensional compactification, if the
original number of Minkowski dimensions equals $8k+1$, $8k+2$ or $8k+3$, and if
there are certain restrictions on the gauge group; these conditions are met by
superstrings. CP may then be broken spontaneously below $10^9$ GeV, explaining
the observed CP violation in the kaon system without inducing a large EDMN. We
discuss the phenomenology of such models, as well as the peculiar nature of
cosmic ``CP strings'' which could be produced at the compactification scale.
Such strings have the curious property that a particle carried around the
string is turned into its CP conjugate. A single CP string renders four
dimensional spacetime nonorientable.
|
hep-ph/9205202
| 727,322 |
One of the aims of this paper is to better explain the philosophy behind the
computations in [E.Bifet, C.De Concini,C.Procesi Cohomology of Regular
Embeddings ] and to place them in a wider conceptual setting. Another aim of
the paper is to outline in the last section an ``equivariant'' approach to some
key results in the theory of toric varieties. The text of the first three
sections follows closely a talk delivered at the University of Copenhagen in
July 1989 on the occasion of the Zeuthen Symposium. This paper is dedicated to
the memory of my friend Pere Menal and will appear in the Fall 1992 issue,
dedicated to his memory, of Publicacions Matem\`atiques, Universitat Aut\`onoma
de Barcelona.
|
alg-geom/9205002
| 727,322 |
A realistic technicolor model is presented with the dynamics below $150$ TeV
treated explicitly. Electroweak symmetry is broken by the condensates of a
`minimal' doublet of technifermions. The new feature of the model is that the
the third generation quarks are unified with the technifermions into multiplets
of a walking gauge force down to a scale of $10$ TeV. The remaining quarks and
leptons are not involved in this unification however. The walking dynamics
enhances the higher dimension interactions which give the ordinary fermions
their masses and mixing, while leaving flavor-changing neutral currents
suppressed. Because the third generation quarks actually feel the walking force
their masses can be much larger than those of the other quarks and the leptons.
The only non-standard particles with masses below several TeV are the single
doublet of technifermions, so electroweak radiative corrections are estimable
and within experimental limits.
|
hep-ph/9205203
| 727,323 |
In this paper the connection between standard perturbation theory techniques
and the new Bern-Kosower calculational rules for gauge theory is clarified. For
one-loop effective actions of scalars, Dirac spinors, and vector bosons in a
background gauge field, Bern-Kosower-type rules are derived without the use of
either string theory or Feynman diagrams. The effective action is written as a
one-dimensional path integral, which can be calculated to any order in the
gauge coupling; evaluation leads to Feynman parameter integrals directly,
bypassing the usual algebra required from Feynman diagrams, and leading to
compact and organized expressions. This formalism is valid off-shell, is
explicitly gauge invariant, and can be extended to a number of other field
theories.
|
hep-ph/9205205
| 727,323 |
We present an exact solution of a 1D model: a particle of incident energy $E$
colliding with a target which is a 1D harmonic ``solid slab'' with $N$ atoms in
its ground state; the Hilbert space of the target is restricted to the ($N+1$)
states with zero or one phonon present. For the case of a short range
interaction, $V(z)$, between the particle and the surface atom supporting a
bound state, an explicit non-perturbative solution of the collision problem is
presented. For finite and large $N$, there is no true sticking but only
so-called Feshbach resonances. A finite sticking coefficient ${\sl s}(E)$ is
obtained by introducing a small phonon decay rate $\eta$ and letting
$N\to\infty$. Our main interest is in the behavior of ${\sl s}(E)$ as $E\to 0$.
For a short range $V(z)$, we find ${\sl s}(E)\sim E^{1/2}$, regardless of the
strength of the particle-phonon coupling. However, if $V(z)$ has a Coulomb
$z^{-1}$ tail, we find ${\sl s}(E)\to\alpha$, where $0 < \alpha < 1$. [A fully
classical calculation gives ${\sl s}(E)\to 1$ in both cases.] We conclude that
the same threshold laws apply to 3D systems of neutral and charged particles
respectively.
|
cond-mat/9205004
| 727,323 |
In bosonic field theories the low-energy scattering of solitons that saturate
Bogomol'nyi-type bounds can be approximated as geodesic motion on the moduli
space of static solutions. In this paper we consider the analogous issue within
the context of supersymmetric field theories. We focus our study on a class of
$N=2$ non-linear sigma models in $d=2+1$ based on an arbitrary K\"ahler target
manifold and their associated soliton or ``lump" solutions. Using a collective
co-ordinate expansion, we construct an effective action which, upon
quantisation, describes the low-energy dynamics of the lumps. The effective
action is an $N=2$ supersymmetric quantum mechanics action with the target
manifold being the moduli space of static charge $N$ lump solutions of the
sigma model. The Hilbert space of states of the effective theory consists of
anti-holomorphic forms on the moduli space. The normalisable elements of the
dolbeault cohomology classes $H^{(0,p)}$ of the moduli space correspond to zero
energy bound states and we argue that such states correpond to bound states in
the full quantum field theory of the sigma model.
|
hep-th/9205008
| 727,323 |
We argue that the \zn phases of hot gauge theories cannot be realized as a
real system with an Hermitean density matrix.
|
cond-mat/9205005
| 727,324 |
We examine the one loop contributions arising in the Two-Higgs-Doublet Model
(THDM) to the W-boson anomalous magnetic dipole and electric quadrupole form
factors for both photon and Z couplings relevant at collider energies. While
the model parameter and $q^2$-dependencies of these form factors are found to
be significant, the corresponding size of these corrections are relatively
small in comparison to unity. They are, however, found to be comparable in
magnitude to the usual Standard Model loop corrections. Radiative corrections
to the Higgs particle masses and couplings due to heavy top-quarks are included
in the analysis.
|
hep-ph/9205207
| 727,324 |
Using the reduced formulation of large-N Quantum Field Theories we study
strings in space-time dimensions higher than one. Some preliminary results
concerning the possible string susceptibilities and general properties of the
model are presented.
|
hep-th/9205010
| 727,324 |
Aim of this paper is to develop a new technique, based on the Baire category
theorem, in order to establish the closure of reachable sets and the existence
of optimal trajectories for control systems, without the usual convexity
assumptions. The bang-bang property is proved for a new class of ``concave"
multifunctions, characterized by the existence of suitable linear selections.
The proofs rely on Lyapunov's theorem in connection with a Baire category
argument.
|
funct-an/9205001
| 727,324 |
We construct a Banach space that does not contain any infinite unconditional
basic sequence.
|
math/9205204
| 727,324 |
We refute the claims made by Chaichian and Smilga in a recent paper in Phys
Rev Letters on the impossibility of spontaneous R Parity breaking. Apart from
explaining their error we summarize the results of a more detailed work that
demonstrates explicitly that R parity can break spontaneously at a scale
anywhere in the range 10 GeV to 1 Tev in a simple extension of the minimal SUSY
standard model proposed previously.
|
hep-ph/9205206
| 727,324 |
The 3D state of strongly correlated electrons is proposed, which in the
external magnetic field $\vec B$ exhibits the fractional quantum Hall effect,
with the zero temperature conductivity tensor $\sigma_{ij} = (e^2/h)(1/m)
\sum_k \epsilon_{ijk} B^k/\mid \vec B\mid $. The analog of Landau and Laughlin
states in 3D are given using quaternion coordinates as generalization of
complex coordinates. We discuss the notion of the fractional statistics in 3D
introduced recently by Haldane.
|
cond-mat/9205006
| 727,324 |
Given two elementary embeddings from the collection of sets of rank less than
$\lambda$ to itself, one can combine them to obtain another such embedding in
two ways: by composition, and by applying one to (initial segments of) the
other. Hence, a single such nontrivial embedding $j$ generates an algebra of
embeddings via these two operations, which satisfies certain laws (for example,
application distributes over both composition and application). Laver has
shown, among other things, that this algebra is free on one generator with
respect to these laws.
The set of critical points of members of this algebra is the subject of this
paper. This set contains the critical point $\kappa_0$ of $j$, as well as all
of the other ordinals $\kappa_n$ in the critical sequence of $j$ (defined by
$\kappa_{n+1} = j(\kappa_n)$). But the set includes many other ordinals as
well. The main result of this paper is that the number of critical points below
$\kappa_n$ (which has been shown to be finite by Laver and Steel) grows so
quickly with $n$ that it dominates any primitive recursive function. In fact,
it grows faster than the Ackermann function, and even faster than a slow
iterate of the Ackermann function. Further results show that, even just below
$\kappa_4$, one can find so many critical points that the number is only
expressible using fast-growing hierarchies of iterated functions (six levels of
iteration beyond exponentials).
|
math/9205202
| 727,325 |
We argue that \CP is a gauge symmetry in string theory. As a consequence, \CP
cannot be explicitly broken either perturbatively or non-pertubatively; there
can be no non-perturbative \CP-violating parameters. String theory is thus an
example of a theory where all $\theta$ angles arise due to spontaneous \CP
violation, and are in principle calculable.
|
hep-th/9205011
| 727,325 |
We establish two-loop (on shell) finiteness of certain supergravity theories
in two dimensions. Possible implications of this result are discussed
|
hep-th/9205012
| 727,325 |
We provide a general description of realisations of W--algebras in terms of
smaller W--algebras and free fields. This is based on the definition of the
W--algebra as the commutant of a set of screening charges. This is conjectured
to be related to partial gauge-fixings in the Hamiltonian reduction model.
|
hep-th/9205013
| 727,325 |
A Banach space E is c_0-saturated if every closed infinite dimensional
subspace of E contains an isomorph of c_0. A c_0-saturated Banach space with an
unconditional basis which has a quotient space isomorphic to l^2 is
constructed.
|
math/9205205
| 727,325 |
Rigorous QCD predictions for decay rates of the P-wave states of heavy
quarkonia are presented. They are based on a new factorization theorem which is
valid to leading order in the heavy quark velocity and to all orders in the
running coupling constant of QCD. The decay rates for all four P states into
light hadronic or electromagnetic final states are expressed in terms of two
phenomenological parameters, whose coefficients are perturbatively calculable.
Logarithms of the binding energy encountered in previous perturbative
calculations of P-wave decays are factored into a phenomenological parameter
that is related to the probability for the heavy quark-antiquark pair to be in
a color-octet S-wave state. Applying these predictions to charmonium, we use
measured decay rates for the $\chione$ and $\chitwo$ to predict the decay rates
of the $\chizero$ and $h_c$.
|
hep-lat/9205006
| 727,325 |
The critical behaviour of the $D=0$ matrix model with potential perturbed by
nonlocal term generating touchings between random surfaces is studied. It is
found that the phase diagram of the model has many features of the phase
diagram of discretized Polyakov's bosonic string with higher order curvature
terms included. It contains the phase of smooth (Liouville) surfaces, the
intermediate phase and the phase of branched polymers. The perturbation becomes
irrelevant at the first phase and dominates at the third one.
|
hep-th/9205014
| 727,325 |
We study limiting lines on degenerations of generic hypersurfaces in $P^n$.
|
alg-geom/9205003
| 727,325 |
We construct an improved version of nonrelativistic QCD for use in lattice
simulations of heavy quark physics, with the goal of reducing systematic errors
from all sources to below 10\%. We develop power counting rules to assess the
importance of the various operators in the action and compute all leading order
corrections required by relativity and finite lattice spacing. We discuss
radiative corrections to tree level coupling constants, presenting a procedure
that effectively resums the largest such corrections to all orders in
perturbation theory. Finally, we comment on the size of nonperturbative
contributions to the coupling constants.
|
hep-lat/9205007
| 727,325 |
The evolution of a closed bosonic string is envisaged in the time-dependent
background of its massless modes. A duality transformation is implemented on
the spatial component of string coordinates to obtain a dual string. It is
shown that the evolution equations are manifestly $O(d,d)$ invariant. The tree
level string effective actions for the original and the dual string theory are
shown to be equivalent.
|
hep-th/9205016
| 727,326 |
We consider the ultra light pseudo Nambu-Goldstone boson appearing in the
late time cosmological phase transition theories as a dark matter candidate.
Since it is almost massless, its nature is more wave like than particle like.
Hence we apply quantum mechanics to study how they form the galactic halos.
Three predictions are made; (1)the mass profile $\rho\sim r^{-1.6}$, (2)there
are ripple-like fine structures in rotation curve, (3) the rotation velocity
times ripple's wave length is largely galaxy independent. We compare the
rotation curves predicted by our theory with the data observed.
|
hep-ph/9205208
| 727,326 |
The Kodaira energy of a polarized manifold (M,L) is defined by
\kappa\epsilon(M,L)=-Inf{t\in Q|\kappa(K+tL)\ge 0}. Here we propose a couple of
conjectures and announce several partial results. 3-dimensional cases are
mainly considered. A hard copy is available on request to the author.
|
alg-geom/9205004
| 727,326 |
Associated selectron-neutralino production in the process $e^-\gamma\to\tilde
e^-\tilde\chi^0$ provides a striking supersymmetric signal: events with a
single high $p_\perp$ electron and otherwise only invisible particles. For
$e^-\gamma$ collisions obtained at high energy linear colliders through
back-scattering of a laser beam, this reaction is shown to be complementary to
selectron pair production in the processes $e^+e^-\to\tilde e^+\tilde e^-$ and
$e^-e^-\to\tilde e^-\tilde e^-$, and to be a probe of heavy selectrons beyond
the kinematical limit of pair production. The standard model background from
$e^-\gamma\to e^-Z^0$ and $W^-\nu$ is studied and substantially reduced by
rapidity and transverse momentum cuts. The minimum required integrated
luminosities for observing this \susic\ signal are given as functions of
several model parameters and collider energies.
|
hep-ph/9205209
| 727,326 |
Scattering amplitudes for discrete states in 2D string theory are considered.
Pole divergences of tree-level amplitudes are extracted and residues are
interpreted as renormalized amplitudes for discrete states. An effective
Lagrangian generating renormalized amplitudes for open string is written and
corresponding Ward identities are presented. A relation of this Lagrangian with
homotopy Lie algebra is discussed.
|
hep-th/9205020
| 727,326 |
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