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The free energy of the Penner model is shown to be closely related to the
integral over the two diagonalizing unitary matrices of a complex rectangular
matrix.
|
hep-th/9206085
| 727,373 |
We propose random matrix models which have $N=\half$ supersymmetry in zero
dimension. The supersymmetry breaks down spontaneously. It is shown that the
double scaling limit can be defined in these models and the breakdown of the
supersymmetry remains in the continuum limit. The exact non-trivial partition
functions of the string theories corresponding to these matrix models are also
obtained.
|
hep-th/9206086
| 727,373 |
We consider Callan, Giddings, Harvey and Strominger's (CGHS) two dimensional
dilatonic gravity with electromagnetic interactions. This model can be also
solved classically. Among the solutions describing static black holes, there
exist extremal solutions which have zero temperatures. In the extremal
solutions, the space-time metric is not singular. We also obtain the solutions
describing charged matter (chiral fermions) collapsing into black holes.
Through the collapsing, not only future horizon but past horizon is also
shifted. The quantum corrections including chiral anomaly are also discussed.
In a way similar to CGHS model, the curvature singularity also appeared, except
extremal case, when the matter collapsing. The screening effects due to the
chiral anomaly have a tendency to cloak the singularity
|
hep-th/9206087
| 727,373 |
After discussing the intrinsic ambiguity in determining the light quark mass
ratio $m_u/m_d$, we reexamine the recent proposal that this ambiguity can be
resolved by applying the QCD multipole expansion for the heavy quarkonium
decays. It is observed that, due to instanton effects, some matrix elements
which have been ignored in previous works can give a significant contribution
to the decay amplitudes, which results in a large uncertainty in the value of
$m_u/m_d$ deduced from quarkonium phenomenology. This uncertainty can be
resolved only by a QCD calculation of some second order coefficients in the
chiral expansion of the decay amplitudes.
|
hep-ph/9206247
| 727,373 |
We propose a general definition of nonequilibrium entropy of a classical
stochastic field. As an example of particular interest in cosmology we apply
this definition to compute the entropy of density perturbations in an
inflationary Universe. On the scales of structures in the Universe, the entropy
of density perturbations dominates over the statistical fluctuations of the
entropy of cosmic microwave photons, indicating the relevance of the entropy of
density fluctuations for structure formation.
|
astro-ph/9206005
| 727,373 |
Macroscopic loop correlators are investigated in the hermitian one matrix
model with the potential perturbed by the higher order curvature term. In the
phase of smooth surfaces the model is equivalent to the minimal conformal
matter coupled to gravity. The properties of the model in the intermediate
phase are similar to that of the discretized bosonic string with the central
charge $C > 1.$ Loop correlators describe the effect of the splitting of the
random surfaces. It is shown, that the properties of the surfaces are changed
in the intermediate phase because the perturbation modifies the spectrum of the
scaling operators.
|
hep-th/9206088
| 727,373 |
We obtain in closed form averages of polynomials, taken over hermitian
matrices with the Gaussian measure involved in the Kontsevich integral, and
prove a conjecture of Witten enabling one to express analogous averages with
the full (cubic potential) measure, as derivatives of the partition function
with respect to traces of inverse odd powers of the external argument. The
proofs are based on elementary algebraic identities involving a new set of
invariant polynomials of the linear group, closely related to the general Schur
functions.
|
hep-th/9206090
| 727,373 |
We compute the weak coupling expansion for the energy of the three
dimensional Ising model through 48 excited bonds. We also compute the
magnetization through 40 excited bonds. This was achieved via a recursive
enumeration of states of fixed energy on a set of finite lattices. We use a
linear combination of lattices with a generalization of helical boundary
conditions to eliminate finite volume effects.
|
hep-lat/9206020
| 727,373 |
The hierarchical nonlinear super-differential equations are identified which
describe universal behavior of the discretized model of $2d$ supergravity
recently proposed. This is done by first taking a double scaling limit of the
super Virasoro constraints ( at finite $N$) of the model and by rederiving it
from the $\tilde{G}_{-1/2}$ constraint and the two reduction of the super KP
hierarchy discussed. The double-scaled constraints are found to be described by
a twisted scalar and a Ramond fermion.
|
hep-th/9206091
| 727,373 |
These days, Franco Iachello is {\it the\/} eminent practitioner applying
classical and finite groups to physics. In this he is following a tradition at
Yale, established by the late Feza Gursey, and succeeding Gursey in the Gibbs
chair; Gursey in turn, had Pauli as a mentor. Iachello's striking achievement
has been to find an actual realization of arcane supersymmetry within mundane
adjacent even-odd nuclei. Thus far this is the only {\it physical\/} use of
supersymmetry, and its fans surely must be surprised at the venue. Here we
describe the role of $SO(2,1)$ conformal symmetry in non-relativistic
Chern--Simons theory: how it acts, how it controls the nature of solutions, how
it expands to an infinite group on the manifold of static solutions thereby
rendering the static problem completely integrable. Since Iachello has also
used the $SO(2,1)$ group in various contexts, this essay is presented to him on
the occasion of his fiftieth birthday.
|
hep-th/9206092
| 727,373 |
Professor M. C. Polivanov and I met only a few times, during my infrequent
visits to the-then Soviet Union in the 1970's and 1980's. His hospitality at
the Moscow Steclov Institute made the trips a pleasure, while the scientific
environment that he provided made them professionally valuable. But it is the
human contact that I remember most vividly and shall now miss after his death.
At a time when issues of conscience were both pressing for attention and
difficult/dangerous to confront, Professor Polivanov made a deep impression
with his quiet but adamant commitment to justice. I can only guess at the
satisfaction he must have felt when his goal of gaining freedom for Yuri Orlov
was attained, and even more so these days when human rights became defensible
in his country; it is regrettable that he cannot now enjoy the future that he
strived to attain.
One of our joint interests was the Liouville theory,$^{1,\,2}$ which in turn
can be viewed as a model for gravity in two-dimensional space-time. Some recent
developments in this field are here summarized and dedicated to Polivanov's
memory, with the hope that he would have enjoyed knowing about them.
|
hep-th/9206093
| 727,373 |
To travel into the past, to observe it, perhaps to influence it and correct
mistakes of one's youth, has been an abiding fantasy of mankind for as long as
we have been aware of a past. Here are described some recent scientific
investigations on this topic.
|
hep-th/9206094
| 727,373 |
We study the nonequilibrium dynamics of line liquids as realized in the
nonlinear motion of flux lines of a superconductor driven by an applied
electric current. Our analysis suggests a transition in the dynamics of the
lines from a smooth, laminar phase at small driving forces, to a rough,
turbulent phase when the drive is increased. We explore the nature of these
phases and describe interesting analogies to driven diffusion and growing
interfaces.
|
cond-mat/9206008
| 727,373 |
We show that a lattice model for induced lattice QCD which was recently
proposed by Kazakov and Migdal has a $Z_N$ gauge symmetry which, in the strong
coupling phase, results in a local confinement where only color singlets are
allowed to propagate along links and all Wilson loops for non-singlets average
to zero. We argue that, if this model is to give QCD in its continuum limit, it
must have a phase transition. We give arguments to support presence of such a
phase transition.
|
hep-th/9206095
| 727,373 |
A simple description of the KP hierarchy and its multi-hamiltonian structure
is given in terms of two Bose currents. A deformation scheme connecting various
W-infinity algebras and relation between two fundamental nonlinear structures
are discussed. Properties of Fa\'a di Bruno polynomials are extensively
explored in this construction. Applications of our method are given for the
Conformal Affine Toda model, WZNW models and discrete KP approach to Toda
lattice chain.
|
hep-th/9206096
| 727,373 |
We present the results of a numerical simulation aimed at understanding the
nature of the `c = 1 barrier' in two dimensional quantum gravity. We study
multiple Ising models living on dynamical $\phi^3$ graphs and analyse the
behaviour of moments of the graph loop distribution. We notice a universality
at work as the average properties of typical graphs from the ensemble are
determined only by the central charge. We further argue that the qualitative
nature of these results can be understood from considering the effect of
fluctuations about a mean field solution in the Ising sector.
|
hep-lat/9206021
| 727,373 |
The subject of this paper is the problem of arrangement of real algebraic
curves on real algebraic surfaces. In this paper we extend Rokhlin,
Kharlamov-Gudkov-Krakhnov and Kharlamov-Marin congruences for curves on
surfaces and give some applications of this extension.
For some pairs consisting of a surface and a curve on this surface (in
particular for M-pairs) we introduce a new structure --- the complex separation
that is separation of the complement of curve into two surfaces. In accordance
with Rokhlin terminology the complex separation is a complex topological
characteristic of real algebraic varieties. The complex separation is similar
to complex orientations introduced by O.Ya.Viro (to the absolute complex
orientation in the case when a curve is empty and to the relative complex
orientation otherwise). In some cases we calculate the complex separation of a
surface (for example in the case when surface is the double branched covering
of another surface along a curve). With the help of these calculations
applications of the extension of Rokhlin congruence gives some new restrictions
for complex orientations of curves on a hyperboloid.
|
alg-geom/9206009
| 727,373 |
The Jacobian for infinitesimal BRST transformations of path integrals for
pure Yang-Mills theory, viewed as a matrix $\unity +\Delta J$ in the space of
Yang-Mills fields and (anti)ghosts, contains off-diagonal terms. Naively, the
trace of $\Delta J$ vanishes, being proportional to the trace of the structure
constants. However, the consistent regulator $\cR$, constructed from a general
method, also contains off-diagonal terms. An explicit computation demonstrates
that the regularized Jacobian $Tr\ \Delta J\exp -\cR /M^2$ for $M^2\rightarrow
\infty $ is the variation of a local counterterm, which we give. This is a
direct proof at the level of path integrals that there is no BRST anomaly.
|
hep-th/9206097
| 727,374 |
In this paper we study arbitrary $W$ algebras related to embeddings of $sl_2$
in a Lie algebra $g$. We give a simple formula for all $W$ transformations,
which will enable us to construct the covariant action for general $W$ gravity.
It turns out that this covariant action is nothing but a Fourier transform of
the WZW action. The same general formula provides a geometrical interpretation
of $W$ transformations: they are just homotopy contractions of ordinary gauge
transformations. This is used to argue that the moduli space relevant to $W$
gravity is part of the moduli space of $G$-bundles over a Riemann surface.
|
hep-th/9206098
| 727,374 |
We compute the critical exponents of $d = 1$ string theory to leading order,
using the renormalization group approach recently suggested by Br\'{e}zin and
Zinn-Justin.
|
hep-th/9206099
| 727,374 |
We examine dynamical mass generation in QCD with large current mass quarks. A
renormalization group analysis is performed to separate fermion self-mass into
a dynamical and a kinematical part. It is shown that the energy scale og the
Schwinger-Dyson (SD) equation and the effective gauge coupling are fixed by the
current mass. The dynamical self-mass satisfies a homogeneous SD equation which
has a trivial solution when the current mass exceeds a critical value. We
therefore suggest that the quark condensate, as the function of the current
mass, observes a local minimum around 2.7\Lambda_(QCD).
|
hep-ph/9206250
| 727,374 |
We study the QCD vacuum orientation angles in correlation with the strong CP
phases. A vacuum alignment equation of the dynamical chiral symmetry breaking
is derived based on the anomalous Ward identity. It is emphasized that a chiral
rotation of the quark field causes a change of the vacuum orientation and a
change in the definition of the light pseudoscalar generators. As an
illustration of the idea, $\h\rightarrow 2\p$ decays are carefully studied in
different chiral frames. Contrary to the claim in Ref.[7], the $\theta$-term
does not directly contribute to the CP-violating processes.
|
hep-ph/9206251
| 727,374 |
A classical two dimensional theory of gravity which has a number of
interesting features (including a Newtonian limit, black holes and
gravitational collapse) is quantized using conformal field theoretic
techniques. The critical dimension depends upon Newton's constant, permitting
models with $d=4$. The constraint algebra and scaling properties of the model
are computed.
|
hep-th/9206100
| 727,374 |
Higher-loop corrections to the pseudoscalar ($0^{-+}$) gluonium correlation
function will be used to obtain the leading gluon condensate contributions to
the subtraction-independent QCD sum-rules. The effect of these higher-loop
corrections on the sum-rule estimates of the pseudoscalar gluonium mass will be
investigated. The final results of this analysis compare favourably with
$SU(3)$ lattice simulations.
|
hep-ph/9206248
| 727,374 |
To investigate order-order interfaces, we perform multimagnetical Monte Carlo
simulations of the $2D$ and $3D$ Ising model. Following Binder we extract the
interfacial free energy from the infinite volume limit of the magnetic
probability density. 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 $F^s = F^s_0 t^\mu$ to be $F^s_0 = 1.52 \pm 0.05$. This
result is in good agreement with a previous MC calculation by Mon, as well as
with experimental results for related amplitude ratios. In addition, we study
in some details the shape of the magnetic probability density for temperatures
below the Curie point.
|
hep-lat/9206022
| 727,374 |
It has been argued that if light Higgs bosons do not exist then the
self--interactions of $W$'s become strong in the TeV region and can be observed
in longitudinal $WW$ scattering. We present a model with many inelastic
channels in the $WW$ scattering process, corresponding to the creation of heavy
fermion pairs. The presence of these heavy fermions affects the elastic
scattering of $W$'s by propagating in loops, greatly reducing the amplitudes in
some charge channels. Consequently, the symmetry--breaking sector cannot be
fully explored by using, for example, the $W^+W^+$ mode alone; all $WW
\rightarrow WW$ scattering modes must be measured.}
|
hep-ph/9206249
| 727,374 |
We develop a coordinate space renormalization of massless Quantum
Electrodynamics using the powerful method of differential renormalization. Bare
one-loop amplitudes are finite at non-coincident external points, but do not
accept a Fourier transform into momentum space. The method provides a
systematic procedure to obtain one-loop renormalized amplitudes with finite
Fourier transforms in strictly four dimensions without the appearance of
integrals or the use of a regulator. Higher loops are solved similarly by
renormalizing from the inner singularities outwards to the global one. We
compute all 1- and 2-loop 1PI diagrams, run renormalization group equations on
them and check Ward identities. The method furthermore allows us to discern a
particular pattern of renormalization under which certain amplitudes are seen
not to contain higher-loop leading logarithms. We finally present the
computation of the chiral triangle showing that differential renormalization
emerges as a natural scheme to tackle $\gamma_5$ problems.
|
hep-ph/9206252
| 727,375 |
A framework allowing for perturbative calculations to be carried out for
quantum field theories with arbitrary smoothly curved boundaries is described.
It is based on an expansion of the heat kernel derived earlier for arbitrary
mixed Dirichlet and Neumann boundary conditions.
The method is applied to a general renormalisable scalar field theory in four
dimensions using dimensional regularisation to two loops and expanding about
arbitrary background fields. Detailed results are also specialised to an $O(n)$
symmetric model with a single coupling constant. Extra boundary terms are
introduced into the action which give rise to either Dirichlet or generalised
Neumann boundary conditions for the quantum fields. For plane boundaries the
resulting renormalisation group functions are in accord with earlier results
but here the additional terms depending on the extrinsic curvature of the
boundary are found. Various consistency relations are also checked and the
implications of conformal invariance at the critical point where the $\beta$
function vanishes are also derived. The local Scr\"odinger equation for the
wave functional defined by the functional integral under deformations of the
boundary is also verified to two loops. Its consistency with the
renormalisation group to all orders in perturbation theory is discussed.
|
cond-mat/9206009
| 727,375 |
Once it is discovered, the determination of the various couplings of a new
neutral gauge boson at a hadron supercollider will not be an easy task. We
review several recent studies that have begun to examine this issue for both
the SSC and LHC.
|
hep-ph/9206258
| 727,375 |
In a recent paper, Chivukula and Golden claimed that the electroweak
symmetry--breaking sector could be hidden if there were many inelastic channels
in the longitudinal $WW$ scattering process. They presented a model in which
the $W$'s couple to pseudo--Goldstone bosons, which may be difficult to detect
experimentally. Because of these inelastic channels, the $WW$ interactions do
not become strong in the TeV region. We demonstrate that, despite the reduced
$WW$ elastic amplitudes in this model, the total event rate ($\sim 5000$ extra
longitudinal $W^+W^-$ pairs produced in one standard SSC year) does not
decrease with an increasing number of inelastic channels, and is roughly the
same as in a model with a broad high--energy resonance and no inelastic
channels.
|
hep-ph/9206254
| 727,375 |
Starting from the new minimal multiplet of supergravity in $2+2$ dimensions,
we construct two types of self-dual supergravity theories. One of them involves
a self-duality condition on the Riemann curvature and implies the equations of
motion following from the Hilbert-Einstein type supergravity action. The other
one involves a self-duality condition on a {\it torsionful} Riemann curvature
with the torsion given by the field-strength of an antisymmetric tensor field,
and implies the equations of motion that follow from an $R^2$-type action.
|
hep-th/9206101
| 727,375 |
The flow of the action induced by changing $N$ is computed in large $N$
matrix models. It is shown that the change in the action is non-analytic. This
non-analyticity appears at the origin of the space of matrices if the action is
even.
|
hep-th/9206102
| 727,375 |
The Heisenberg antiferromagnet, which arises from the large $U$ Hubbard
model, is investigated on the $C_{60}$ molecule and other fullerenes. The
connectivity of $C_{60}$ leads to an exotic classical ground state with
nontrivial topology. We argue that there is no phase transition in the Hubbard
model as a function of $U/t$, and thus the large $U$ solution is relevant for
the physical case of intermediate coupling. The system undergoes a first order
metamagnetic phase transition. We also consider the S=1/2 case using
perturbation theory. Experimental tests are suggested.
|
cond-mat/9206010
| 727,375 |
In the canonical up-quark seesaw, the ratios of light neutrino masses are
more easily predicted than the masses themselves. Under explicitly enumerated
neccesary but minimal assumptions, these ratios are obtained, including
radiative corrections. The predictions remain uncertain only by the top quark
mass and triviality mass limit, and the power law of the seesaw. The tau
neutrino is specially affected by the non-linear effect of the heavy top quark
mass. The derived ratios have application to solar, atmospheric, and
cosmological neutrinos and laboratory neutrino oscillation searches. The seesaw
with charged lepton masses instead is briefly considered. Submitted to Phys
Lett B.
|
hep-ph/9206256
| 727,375 |
In Hawking's Euclidean path integral approach to quantum gravity, the
partition function is computed by summing contributions from all possible
topologies. The behavior such a sum can be estimated in three spacetime
dimensions in the limit of small cosmological constant. The sum over topologies
diverges for either sign of $\Lambda$, but for dramatically different reasons:
for $\Lambda>0$, the divergent behavior comes from the contributions of very
low volume, topologically complex manifolds, while for $\Lambda<0$ it is a
consequence of the existence of infinite sequences of relatively high volume
manifolds with converging geometries. Possible implications for
four-dimensional quantum gravity are discussed.
|
hep-th/9206103
| 727,375 |
The antiferromagnetic Heisenberg Hamiltonian is investigated on a truncated
tetrahedron, which is a closed 12 site system. We find that the ground state
has many similarities to that of $C_{60}$. We study 2- and 4-spin correlations
in the classical ground state of the truncated tetrahedron and calculate the
same correlations in the exact S=1/2 ground state. We find that the classical
correlations survive for a range of bond strengths in the Heisenberg
Hamiltonian and that one can construct a good trial wavefunction based on the
classical ground state. This suggests that the correlations present in the
classical ground state of $C_{60}$ also survive in the exact ground state of
that system, for a range of bond strengths about the physically relevant $J_2
\approx J_1$. We calculate the momentum-space correlation function $S ( q )$,
which is measurable by neutron scattering, for both $C_{12}$ and $C_{60}$. We
also calculate correlations at finite temperature.
|
cond-mat/9206011
| 727,375 |
We consider radiative corrections to the decay rate $\Gamma(H\rightarrow ZZ)$
of the heavy {\it CP}-even Higgs boson of the minimal supersymmetric model to
two $Z$ bosons. We perform a one loop Feynman diagram calculation in the
on-mass-shell renormalization scheme, and include the third generation of
quarks and squarks. The tree level rate is suppressed by a mixing angle factor
and decreases as $1/M_H$ for large $M_H$. The corrected rate overcomes this
suppression and increases with $M_H$ for $M_H > 500$~GeV. The corrections can
be very large and depend in detail on the top squark masses and $A$-term, as
well as the supersymmetric Higgs mass parameter $\mu$.
|
hep-ph/9206257
| 727,375 |
We investigate the embedding variable approach to geometrodynamics advocated
in work by Isham, Kucha\v{r} and Unruh for a general class of coordinate
conditions that mirror the Isham-Kucha\v{r} Gaussian condition but allow for
arbitrary algebraic complexity. We find that the same essential structure
present in the ultralocal Gaussian condition is repeated in the general case.
The resultant embedding--extended phase space contains a full representation of
the Lie algebra of the spacetime diffeomorphism group as well as a consistent
pure gravity sector.
|
hep-th/9206105
| 727,375 |
We study the hadronic spectrum in quenched lattice QCD using an improved
Wilson fermion action (Hamber-Wu(1983),Eguchi-Kawamoto(1984)) at $\beta= 5.7$
and $\beta =6.0$. We find a systematic reduction of the finite spacing effects
compared to the results obtained by using the standard Wilson action.
|
hep-lat/9206023
| 727,376 |
Recent progress in the theory of the electroweak phase transition is
discussed. For the Higgs boson mass smaller than the masses of W and Z bosons,
the phase transition is of the first order. However, its strength is
approximately 2/3 times less than what follows from the one-loop approximation.
This rules out baryogenesis in the minimal version of the electroweak theory
with light Higgs bosons. The possibility of the strongly first order phase
transition in the theory with superheavy Higgs bosons is considered.
We show that if the Yang-Mills field at high temperature acquires a magnetic
mass $\sim g^2 T$, then no linear terms appear in the effective potential in
all orders of perturbation theory and the symmetry in gauge theories at high
temperatures is actually restored. Even though the last statement was never
questioned by most of the authors, it was extremely difficult to come to a
reliable conclusion about it due to the infrared problem in thermodynamics of
non-Abelian gauge fields.
The phase transition occurs due to production and expansion of critical
bubbles. A general analytic expression for the probability of the bubble
formation is obtained, which may be used for study of tunneling in a wide class
of theories.
|
hep-ph/9206259
| 727,378 |
The Four Fermi model with discrete chiral symmetry is studied in three
dimensions at non-zero chemical potential and temperature using the Hybrid
Monte Carlo algorithm. The number of fermion flavors is chosen large $(N_f=12)$
to compare with analytic results. A first order chiral symmetry restoring
transition is found at zero temperature with a critical chemical potential
$\mu_c$ in good agreement with the large $N_f$ calculations. The critical index
$\nu$ of the correlation length is measured in good agreement with analytic
calculations. The two dimensional phase diagram (chemical potential vs.
temperature) is mapped out quantitatively. Finite size effects on relatively
small lattices and non-zero fermion mass effects are seen to smooth out the
chiral transition dramatically.
|
hep-lat/9206024
| 727,378 |
If stable electroweak strings are copiously produced during the electroweak
phase transition, they may contribute significantly to the presently observed
baryon to entropy ratio of the universe. This analysis establishes the
feasibility of implementing an electroweak baryogenesis scenario without a
first order phase transition.
|
hep-ph/9206260
| 727,378 |
We produce the general solution of the Wess-Zumino consistency condition for
gauge theories of the Yang-mills type, for any ghost number and form degree. We
resolve the problem of the cohomological independence of these solutions. In
other words we fully describe the local version of the cohomology of the BRS
operator, modulo the differential on space--time. This in particular includes
the presence of external fields and non--trivial topologies of space--time.
|
hep-th/9206106
| 727,378 |
We analyse in detail the $SL(2,R)$ black hole by extending standard
techniques of Kac-Moody current algebra to the non-compact case. We construct
the elements of the ground ring and exhibit W-infinity type structure in the
fusion algebra of the discrete states. As a consequence, we can identify some
of the exactly marginal deformations of the black hole. We show that these
deformations alter not only the spacetime metric but also turn on non-trivial
backgrounds for the tachyon and all of the massive modes of the string.
|
hep-th/9206107
| 727,378 |
We study the $O(4)$-symmetric $ \Phi^4 $-theory in the scaling region of the
broken phase using the standard and a Symanzik improved action with infinite
bare self-coupling $\lambda$. A high precision Monte Carlo simulation is
performed by applying the reflection cluster algorithm. Employing the histogram
method we analytically continue to a sequence of values of the hopping
parameter $\kappa$ neighbouring the actually simulated ones. In the
investigated vicinity of the critical point $\kappa_{c}$ finite volume effects
affecting, e.g., the determination of the field expectation value $\Sigma$ and
the mass $m_\sigma$ of the $\sigma$-particle are very well described by 1-loop
renormalized perturbation theory. We carry out a detailed scaling analysis on a
high level of precision. Finally we discuss the upper bound on the Higgs mass
for both kinds of actions.
|
hep-lat/9206025
| 727,378 |
We use chiral perturbation theory to show that pseudo-Goldstone boson
scattering and gluon fusion probe different aspects of electroweak symmetry
breaking at hadron colliders. In particular, the physics responsible for
unitarizing the lowest-order pseudo-Goldstone boson scattering amplitudes need
not significantly affect the gluon fusion process. We first show this within
the context of strict chiral perturbation theory, and then discuss it using the
language of resonances.
|
hep-ph/9206261
| 727,378 |
The nonlinear scalar-field realisation of $w_{1+\infty}$ symmetry in $d=2$
dimensions is studied in analogy to the nonlinear realisation of $d=4$
conformal symmetry $SO(4,2)$. The $w_{1+\infty}$ realisation is derived from a
coset-space construction in which the divisor group is generated by the
non-negative modes of the Virasoro algebra, with subsequent application of an
infinite set of covariant constraints. The initial doubly-infinite set of
Goldstone fields arising in this construction is reduced by the covariant
constraints to a singly-infinite set corresponding to the Cartan-subalgebra
generators $v^\ell_{-(\ell+1)}$. We derive the transformation rules of this
surviving set of fields, finding a triangular structure in which fields
transform into themselves or into lower members of the set only. This
triangular structure gives rise to finite-component subrealisations, including
the standard one for a single scalar. We derive the Maurer-Cartan form and
discuss the construction of invariant actions.
|
hep-th/9206108
| 727,378 |
We demonstrate that the ability to polarize the photons produced by
back-scattering laser beams at a TeV scale linear $\epem$ collider could make
it possible to determine whether or not a neutral Higgs boson produced in
photon-photon collisions is a CP eigenstate. The relative utility of different
types of polarization is discussed. Asymmetries that are only non-zero if the
Higgs boson is a CP mixture are defined, and their magnitudes illustrated for a
two-doublet Higgs model with CP-violating neutral sector.
|
hep-ph/9206262
| 727,378 |
We present explicit expressions for the Maurer-Cartan forms of the
superdiffeomorphism group associated to a super Riemann surface. As an
application to superconformal field theory, we use these forms to evaluate the
effective action for the factorized superdiffeomorphism anomaly.
|
hep-th/9206109
| 727,378 |
In the first part of this paper we investigate the operator aspect of
higher-rank supersymmetric model which is introduced as a Lie theoretic
extension of the $N=2$ minimal model with the simplest case $su(2)$
corresponding to the $N=2$ minimal model.
In particular we identify the analogs of chirality conditions and chiral
ring. In the second part we construct a class of topological conformal field
theories starting with this higher-rank supersymmetric model. We show the
BRST-exactness of the twisted stress-energy tensor, find out physical
observables and discuss how to make their correlation functions. It is
emphasized that in the case of $su(2)$ the topological field theory constructed
in this paper is distinct from the one obtained by twisting the $N=2$ minimal
model through the usual procedure.
|
hep-th/9206110
| 727,379 |
We analyze the new states that have recently been discovered in 2D string
theory by E. Witten and B. Zwiebach. Since the Liouville direction is
uncompactified, we show that the deformations by the new ghost number two
states generate equivalent classical solutions of the string fields. We argue
that the new ghost number one states are responsible for generating
transformations which relate such equivalent solutions. We also discuss the
possible interpretation of higher ghost number states of those kinds.
|
hep-th/9206111
| 727,379 |
Finite size scaling studies of monopole condensation in noncompact quenched
lattice $QED$ indicate an authentic second order phase transition lying in the
universality class of four dimensional percolation. Since the upper critical
dimension of percolation is six, the measured critical indices are far from
mean-field values. We propose a simple set of ratios as the exact critical
indices for this transition. The implication of these results for critical
points in Abelian gauge theories are discussed.
|
hep-lat/9206026
| 727,379 |
We present the results of a Monte--Carlo simulation of the $G_2^{(1)}$ Affine
Toda field theory action in two dimensions. We measured the ratio of the masses
of the two fundamental particles as a function of the coupling constant. Our
results strongly support the conjectured duality with the $D_4^{(3)}$ theory,
and are consistent with the mass formula of Delius et al.
|
hep-th/9206112
| 727,379 |
We review some recent work on nonperturbative properties of fermions and
connections with chiral gauge theories. In particular, we consider one of the
ultimate goals of this program: the understanding of the actual fermion mass
spectrum. It is pointed out that if quarks and leptons are composite, their
masses may be set by the physics of the preons and their interactions in such a
manner as to differ considerably from the Yukawa form $m_f \propto v$ (where
$v$ is the electroweak symmetry breaking scale) or analogous forms involving
$v$. Some ideas of how this might work are given, and some implications are
discussed.
|
hep-ph/9206264
| 727,379 |
We report on a lattice QCD estimate of the quark spin fraction of the proton
spin. The estimate is arrived at by means of a lattice QCD simulation of the
polarized proton matrix element of the Adler-Bell-Jackiw anomaly. The
preliminary result of the simulation is that this fraction is rather small.
This is in accord with the interpretation of the EMC experiment that the quark
spins are responsible for very little, if any, of the proton spin. (Talk given
at the Adriatico Research Conference on Polarization Dynamics in Nuclear and
Particle Physics, Trieste, January, 1992) NOTE: This paper is available only in
postscript form.
|
hep-lat/9206027
| 727,379 |
Requirement that the vacuum expectation values of Higgs fields immediately
after the phase transition be large enough imposes constraints upon the
parameters of the minimal supersymmetric model. In particular, one obtains the
upper bound on the lighter CP-even Higgs mass and the soft supersymmetry
breaking scale for different values of the top quark mass.
|
hep-ph/9206266
| 727,379 |
The purpose of this note is to attach a name to a natural class of
combinatorial problems and to point out that this class includes many important
special cases. We also show that a simple problem of placing nonoverlapping
labels on a rectangular map is NP-complete.
|
cs/9301116
| 727,380 |
We carry over to a quite general noncommutative setting some of the basic
tools of differential geometry, using from the very beginning the setting of
convenient vector spaces developed by Froelicher and Kriegl, which allows to
carry all of multilinear algebra into this kind of functional analysis with
suitably completed tensor products. In the first section we give a short
description of the setting of convenient spaces elaborating those aspects which
are needed later. Then we repeat the usual construction of noncommutative
differential forms for convenient algebras. Next they show that the bimodule
$\Omega\sb n (A)$ of universal non-commutative $n$-forms represents the functor
of the normalized Hochschild $n$-cocycles. In the third section we introduce
the noncommutative version of the Froelicher-Nijenhuis bracket by investigating
all bounded graded derivations of the algebra of differential forms. This
bracket is then used to formulate the concept of integrability and
involutiveness for distributions and to indicate a route towards a theorem of
Frobenius. This is then used to discuss bundles and connections in the
noncommutative setting and to go some steps towards a noncommutative Chern-Weil
homomorphism. In the final section we give a brief description of the
noncommutative version of the Schouten-Nijenhuis bracket and describe Poisson
structures.
|
math/9207209
| 727,380 |
The author surveys Galois theory of function fields with non-zero
caracteristic and its relation to the structure of finite permutation groups
and matrix groups.
|
math/9207210
| 727,380 |
We discuss two generalizations of the collar lemma. The first is the stable
neighborhood theorem which says that a (not necessarily simple) closed geodesic
in a hyperbolic surface has a \lq\lq stable neighborhood\rq\rq whose width only
depends on the length of the geodesic. As an application, we show that there is
a lower bound for the length of a closed geodesic having crossing number $k$ on
a hyperbolic surface. This lower bound tends to infinity with $k$. Our second
generalization is to totally geodesic hypersurfaces of hyperbolic manifolds.
Namely, we construct a tubular neighborhood function and show that an embedded
closed totally geodesic hypersurface in a hyperbolic manifold has a tubular
neighborhood whose width only depends on the area of the hypersurface (and
hence not on the geometry of the ambient manifold). The implications of this
result for volumes of hyperbolic manifolds is discussed. We also derive a
(hyperbolic) quantitative version of the Klein-Maskit combination theorem (in
all dimensions) for free products of fuchsian groups. Using this last theorem,
we construct examples to illustrate the qualitative sharpness of the tubular
neighborhood function.
|
math/9207211
| 727,380 |
The notion of viscosity solutions of scalar fully nonlinear partial
differential equations of second order provides a framework in which startling
comparison and uniqueness theorems, existence theorems, and theorems about
continuous dependence may now be proved by very efficient and striking
arguments. The range of important applications of these results is enormous.
This article is a self-contained exposition of the basic theory of viscosity
solutions.
|
math/9207212
| 727,380 |
Certain solvable extensions of $H$-type groups provide noncompact
counterexamples to the so-called Lichnerowicz conjecture, which asserted that
``harmonic'' Riemannian spaces must be rank 1 symmetric spaces.
|
math/9207213
| 727,380 |
A ``self--similar'' example is constructed that shows that a conjecture of N.
U. Arakelyan on the order of decrease of deficiencies of an entire function of
finite order is not true.
|
math/9207214
| 727,380 |
We use an extension of Sunada's theorem to construct a nonisometric pair of
isospectral simply connected domains in the Euclidean plane, thus answering
negatively Kac's question, ``can one hear the shape of a drum?'' In order to
construct simply connected examples, we exploit the observation that an
orbifold whose underlying space is a simply connected manifold with boundary
need not be simply connected as an orbifold.
|
math/9207215
| 727,380 |
We describe briefly a new approach to some problems related to Teichm\"uller
spaces, invariant metrics, and extremal quasiconformal maps. This approach is
based on the properties of plurisubharmonic functions, especially of the
plurisubharmonic Green function. The main theorem gives an explicit
representation of the Green function for Teichm\"uller spaces by the
Kobayashi-Teichm\"uller metric of these spaces. This leads to various
applications. In particular, this gives a new characterization of extremal
quasiconformal maps.
|
math/9207216
| 727,380 |
We give a classification of the $p$--local stable homotopy type of $BG$,
where $G$ is a finite group, in purely algebraic terms. $BG$ is determined by
conjugacy classes of homomorphisms from $p$--groups into $G$. This
classification greatly simplifies if $G$ has a normal Sylow $p$--subgroup; the
stable homotopy types then depends only on the Weyl group of the Sylow
$p$--subgroup. If $G$ is cyclic mod $p$ then $BG$ determines $G$ up to
isomorphism. The last class of groups is important because in an appropriate
Grothendieck group $BG$ can be written as a unique linear combination of
$BH$'s, where $H$ is cyclic mod $p$.
|
math/9207217
| 727,380 |
The method of rational function certification for proving terminating
hypergeometric identities is extended from single sums or integrals to
multi-integral/sums and ``$q$'' integral/sums.
|
math/9207218
| 727,380 |
The polynomials that arise as coefficients when a power series is raised to
the power $x$ include many important special cases, which have surprising
properties that are not widely known. This paper explains how to recognize and
use such properties, and it closes with a general result about approximating
such polynomials asymptotically.
|
math/9207221
| 727,380 |
We develop a phase space path-integral approach for deriving the Lagrangian
realization of the models defined by Hamiltonian reduction of the WZNW theory.
We illustrate the uses of the approach by applying it to the models of
non-Abelian chiral bosons, $W$-algebras and the GKO coset construction, and
show that the well-known Sonnenschein's action, the generalized Toda action and
the gauged WZNW model are precisely the Lagrangian realizations of those
models, respectively.
|
hep-th/9206113
| 727,380 |
We study the implications of duality symmetry on the analyticity properties
of the partition function as it depends upon the compactification length. In
order to obtain non-trivial compactifications, we give a physical prescription
to get the Helmholtz free energy for any heterotic string supersymmetric or
not. After proving that the free energy is always invariant under the duality
transformation $R\rightarrow \alpha^{'}/(4R)$ and getting the zero temperature
theory whose partition function corresponds to the Helmholtz potential, we show
that the self-dual point $R_{0}=\sqrt{\alpha^{'}}/2$ is a generic singularity
as the Hagedorn one. The main difference between these two critical
compactification radii is that the term producing the singularity at the
self-dual point is finite for any $R \neq R_{0}$. We see that this behavior at
$R_{0}$ actually implies a loss of degrees of freedom below that point.
|
hep-th/9207002
| 727,380 |
We use path-\-integral methods to derive the ground state wave functions of a
number of two-\-dimensional fermion field theories and related systems in
one-\-dimensional many body physics. We derive the exact wave function for the
Thirring/Luttinger and Coset fermion models and apply our results to derive the
universal behavior of the wave functions of the Heisenberg antiferromagnets and
of the Sutherland model. We find explicit forms for the wave functions in the
density and in the Grassmann representations. We show that these wave functions
always have the Jastrow factorized form and calculated the exponent. Our
results agree with the exponents derived from the Bethe Ansatz for the
Sutherland model and the Haldane-\-Shastri spin chain but apply to all the
systems in the same universality class.
|
hep-th/9207003
| 727,380 |
We report on a high precision Montecarlo test of the three dimensional Ising
gauge model at finite temperature. The string tension $\sigma$ is extracted
from the expectation values of correlations of Polyakov lines. Agreement with
the string tension extracted from Wilson loops is found only if the quantum
fluctuations of the flux tube are properly taken into account. The central
charge of the underlying conformal field theory is c=1.
|
hep-lat/9207001
| 727,380 |
The XXVII$^{\rm th}$ Rencontres de Moriond featured approximately 84 talks on
a wide range of topics. I will try to summarize the highlights under the
hypothesis that $SU_3 \x SU_2 \x U_1$ is correct to first approximation,
concentrating on probes for new physics at various scales.
|
hep-ph/9207201
| 727,380 |
We provide a method to test if hadrons produced in high energy heavy ion
collisions were emitted at freeze-out from an equilibrium hadron gas. Our
considerations are based on an ideal gas at fixed temperature $T_f$, baryon
number density $n_B$, and vanishing total strangeness. The constituents of this
gas are all hadron resonances up to a mass of 2 GeV; they are taken to decay
according to the experimentally observed branching ratios. The ratios of the
various resulting hadron production rates are tabulated as functions of $T_f$
and $n_B$. These tables can be used for the equilibration analysis of any heavy
ion data; we illustrate this for some specific cases.
|
hep-ph/9207204
| 727,381 |
A system of particles hopping on a line, singly or as merged pairs, and
annihilating in groups of three on encounters, is solved exactly for certain
symmetrical initial conditions. The functional form of the density is nearly
identical to that found in two-body annihilation, and both systems show
non-mean-field, ~1/t**(1/2) instead of ~1/t, decrease of particle density for
large times.
|
cond-mat/9207001
| 727,381 |
The tensionless limit of the free bosonic string is space-time conformally
symmetric classically. Requiring invariance of the quantum theory in the light
cone gauge tests the reparametrization symmetry needed to fix this gauge. The
full conformal symmetry gives stronger constraints than the Poincar\'e
subalgebra. We find that the symmetry may be preserved in any space-time
dimension, but only if the spectrum is drastically reduced (part of this
reduction is natural in a zero tension limit of the ordinary string spectrum).
The quantum states are required to be symmetric ({\it i.e.} singlets) under
space-time diffeomorphisms, except for the centre of mass wave function.
|
hep-th/9207005
| 727,381 |
We study canonical quantization of a class of 2d dilaton gravity models,
which contains the model proposed by Callan, Giddings, Harvey and Strominger. A
set of non-canonical phase space variables is found, forming an $SL(2,{\bf R})
\times U(1)$ current algebra, such that the constraints become quadratic in
these new variables. In the case when the spatial manifold is compact, the
corresponding quantum theory can be solved exactly, since it reduces to a
problem of finding the cohomology of a free-field Virasoro algebra. In the
non-compact case, which is relevant for 2d black holes, this construction is
likely to break down, since the most general field configuration cannot be
expanded into Fourier modes. Strategy for circumventing this problem is
discussed.
|
hep-th/9207006
| 727,381 |
We present exact results for a lattice model of cluster growth in 1D. The
growth mechanism involves interface hopping and pairwise annihilation
supplemented by spontaneous creation of the stable-phase, +1, regions by
overturning the unstable-phase, -1, spins with probability p. For cluster
coarsening at phase coexistence, p=0, the conventional structure-factor scaling
applies. In this limit our model falls in the class of diffusion-limited
reactions A+A->inert. The +1 cluster size grows diffusively, ~t**(1/2), and the
two-point correlation function obeys scaling. However, for p>0, i.e., for the
dynamics of formation of stable phase from unstable phase, we find that
structure-factor scaling breaks down; the length scale associated with the size
of the growing +1 clusters reflects only the short-distance properties of the
two-point correlations.
|
cond-mat/9207002
| 727,381 |
We present an introduction to modern theories of interfacial fluctuations and
the associated interfacial parameters: surface tension and surface stiffness,
as well as their interpretation within the capillary wave model. Transfer
matrix spectrum properties due to fluctuation of an interface in a
long-cylinder geometry are reviewed. The roughening transition and properties
of rigid interfaces below the roughening temperature in 3d lattice models are
surveyed with emphasis on differences in fluctuations and transfer matrix
spectral properties of rigid vs. rough interfaces.
|
cond-mat/9207003
| 727,381 |
The lightest CP-even Higgs boson $h$ in the minimum supersymmetric standard
model (MSSM) has a mass upper bound depending on the top quark and squark
masses. An $e^+e^-$ collider with enough energy and luminosity to produce $h+Z$
at measurable rates up to the maximum $h$ mass would cover the entire MSSM
parameter space, if $h+A$ production was also searched for. We explore the
energy and/or luminosity needed for various top quark and squark masses. For
$m_t=150$\,GeV and 1\,TeV SUSY mass scale, a 230\,GeV collider with
10\,fb$^{-1}$ luminosity would suffice.
|
hep-ph/9207205
| 727,381 |
The decay of charmed mesons into pseudoscalar (P) and vector (V) mesons is
studied in the context of nonet symmetry. We have found that it is badly broken
in the PP channels and in the P sector of the PV channels as expected from the
non-ideal mixing of the \eta and the \eta'. In the VV channels, it is also
found that nonet symmetry does not describe the data well. We have found that
this discrepancy cannot be attributed entirely to SU(3) breaking at the usual
level of 20--30%. At least one, or both, of nonet and SU(3) symmetry must be
very badly broken. The possibility of resolving the problem in the future is
also discussed.
|
hep-ph/9207206
| 727,381 |
We show that charged Eguchi-Hanson instantons provide a concrete and
calculable new source of intrinsic Peccei-Quinn symmetry breaking by quantum
gravity. The size of this breaking is shown to depend sensitively on the short
distance details of a given theory, but is generically suppressed by fermion
zero modes. Demanding that these gravitational effects not affet the axion
solution to the strong CP problem, we find that at least two sets of quarks
with differing Peccei-Quinn charges are required. In addition, these effects
obviate the cosmological axion domain wall problem but leave unchanged problems
associated with coherent axion oscillations.
|
hep-ph/9207208
| 727,382 |
We construct the enveloping fundamental spin model of the t-J hamiltonian
using the Quantum Inverse Scattering Method (QISM), and present all three
possible Algebraic Bethe Ans\"atze. Two of the solutions have been previously
obtained in the framework of Coordinate Space Bethe Ansatz by Sutherland and by
Schlottmann and Lai, whereas the third solution is new. The formulation of the
model in terms of the QISM enables us to derive explicit expressions for higher
conservation laws.
|
hep-th/9207007
| 727,382 |
In conjunction with recent numerical \hbox{$\lambda~\partial_0 A_0 +
\nabla\cdot\vec{A} =0$} ``$\lambda$-gauge'' results reported in a companion
paper, we construct an $N\to\infty$ Wilson loop picture of
$\lambda$-gaugefixing in which (I)the $\lambda$-gauge expectation value of a
link chain $C$ is the weighted sum over Wilson loops made by joining to $C$ all
selfavoiding chains $\widetilde{C}$ closing $C$. (II)Weights
$A_{\widetilde{C}}$, containing all the $\lambda$-dependence, are given by the
$\beta=0$ $\lambda$-gauge expectation value of $\widetilde{C}$.
(III)$A_{\widetilde{C}}$ equals path-products of coefficients from the trace
expansion of the gaugefixing Boltzmann weight. From (II) and (III) we deduce
formulas for $\beta =0$ quark matrix elements. We find that $M_q^{(\lambda)}$
decreases with increasing $\lambda$; the quark propagator dispersion relation
is not covariant when $\lambda\ne 1$; and $\Delta I=1/2$ matching coefficients
are $\lambda$-independent. These strong coupling features are qualitatively
consistent with numerical $\beta=5.7$ and $6.0$ results briefly described here
for comparison purposes but mainly presented in a companion paper.
|
hep-lat/9207002
| 727,382 |
The two--dimensional topological BF model is considered in the Landau gauge
in the framework of perturbation theory. Due to the singular behaviour of the
ghost propagator at long distances, a mass term to the ghost fields is
introduced as infrared regulator. Relying on the supersymmetric algebraic
structure of the resulting massive theory, we study the infrared and
ultraviolet renormalizability of the model, with the outcome that it is
perturbatively finite.
|
hep-th/9207008
| 727,382 |
We develop a new fast-diffusion approximation for the kinetics of deposition
of extended objects on a linear substrate, accompanied by diffusional
relaxation. This new approximation plays the role of the mean-field theory for
such processes and is valid over a significantly larger range than an earlier
variant, which was based on a mapping to chemical reactions. In particular,
continuum-limit off-lattice deposition is described naturally within our
approximation. The criteria for the applicability of the mean-field theory are
derived. While deposition of dimers, and marginally, trimers, is affected by
fluctuations, we find that the k-mer deposition kinetics is asymptotically
mean-field like for all k=4,5,..., where the limit k->infinity, when properly
defined, describes deposition-diffusion kinetics in the continuum.
|
cond-mat/9207004
| 727,382 |
Color transparency CT depends on the formation of a wavepacket of small
spatial extent. It is useful to interpret experimental searches for CT with a
multiple scattering scattering series based on wavepacket-nucleon scattering
instead of the standard one using nucleon-nucleon scattering. We develop
several new techniques which are valid for differing ranges of energy. These
techniques are applied to verify some early approximations; study new forms of
the wave-packet-nucleon interaction; examine effects of treating wave packets
of non-zero size; and predict the production of $N^*$'s in electron scattering
experiments.
|
hep-ph/9207210
| 727,382 |
We study the classical and quantum $G$ extended superconformal algebras from
the hamiltonian reduction of affine Lie superalgebras, with even subalgebras
$G\oplus sl(2)$. At the classical level we obtain generic formulas for the
Poisson bracket structure of the algebra. At the quantum level we get free
field (Feigin-Fuchs) representations of the algebra by using the BRST formalism
and the free field realization of the affine Lie superalgebra. In particular we
get the free field representation of the $sl(2)\oplus sp(2N)$ extended
superconformal algebra from the Lie superalgebra $osp(4|2N)$. We also discuss
the screening operators of the algebra and the structure of singular vectors in
the free field representation.
|
hep-th/9207009
| 727,382 |
We present explicit free field representations for the $N=4$ doubly extended
superconformal algebra, $\tilde{\cal{A}}_{\gamma}$. This algebra generalizes
and contains all previous $N=4$ superconformal algebras. We have found
$\tilde{\cal{A}}_{\gamma}$ to be obtained by hamiltonian reduction of the Lie
superalgebra $D(2|1;\alpha)$. In addition, screening operators are explicitly
given and the associated singular vectors identified. We use this to present a
natural conjecture for the Kac determinant generalizing a previous conjecture
by Kent and Riggs for the singly extended case. The results support and
illuminate several aspects of the characters of this algebra previously
obtained by Taormina and one of us.
|
hep-th/9207010
| 727,382 |
Color transparency occurs if a small-sized wave packet, formed in a high
momentum transfer process, escapes the nucleus before expanding. The time
required for the expansion depends on the masses of the baryonic components of
the wave packet. Measured proton diffractive dissociation and electron deep
inelastic scattering cross sections are used to examine and severely constrain
the relevant masses. These constraints allow significant color transparency
effects to occur at experimentally accessible momentum transfers.
|
hep-ph/9207211
| 727,382 |
We consider a class of simplest Majoron models where neutrino- majoron
couplings can be in the range $g \sim 10^{-5}-10^{-3}$ leading to the
observability of neutrinoless double beta decay with majoron emission. The
majoron is a singlet of the electroweak gauge symmetry, thus avoiding conflict
with the LEP data on Z decay, which rules out the triplet and doublet majoron
models.
|
hep-ph/9207209
| 727,382 |
We study the kinematics of multigrid Monte Carlo algorithms by means of
acceptance rates for nonlocal Metropolis update proposals. An approximation
formula for acceptance rates is derived. We present a comparison of different
coarse-to-fine interpolation schemes in free field theory, where the formula is
exact. The predictions of the approximation formula for several interacting
models are well confirmed by Monte Carlo simulations. The following rule is
found: For a critical model with fundamental Hamiltonian H(phi), absence of
critical slowing down can only be expected if the expansion of <H(phi + psi)>
in terms of the shift psi contains no relevant (mass) term. We also introduce a
multigrid update procedure for nonabelian lattice gauge theory and study the
acceptance rates for gauge group SU(2) in four dimensions.
|
hep-lat/9207003
| 727,382 |
We apply the method of coadjoint orbits of \winf-algebra to the problem of
non-relativistic fermions in one dimension. This leads to a geometric
formulation of the quantum theory in terms of the quantum phase space
distribution of the fermi fluid. The action has an infinite series expansion in
the string coupling, which to leading order reduces to the previously discussed
geometric action for the classical fermi fluid based on the group $w_\infty$ of
area-preserving diffeomorphisms. We briefly discuss the strong coupling limit
of the string theory which, unlike the weak coupling regime, does not seem to
admit of a two dimensional space-time picture. Our methods are equally
applicable to interacting fermions in one dimension.
|
hep-th/9207011
| 727,382 |
The prospects for discovery of the five Higgs bosons of the minimal
supersymmetric standard model are assessed for existing and planned future
colliders, including LEP\,I, LEP\,II, LHC and SSC. As a benchmark for
comparisons, we take a top-quark mass $m_t= 150\,$GeV and squark mass parameter
$\tilde m= 1\,$TeV in evaluating one-loop radiative corrections; some results
for other $m_t$ values are also given. Searches based on the most promising
production and decay channels are taken into account. For large regions in
parameter space, detectable signals are predicted for one or more of the Higgs
bosons, but there remains a region for which no signals would be visible at the
above colliders.
|
hep-ph/9207212
| 727,382 |
A two-boson realization of the second hamiltonian structure for the KP
hierarchy has recently appeared in the literature. Furthermore, it has been
claimed that this is also a realization of the hierarchy itself. This is
surprising because it would mean that the dynamics of the KP hierarchy---which
in its usual formulation requires an infinite number of fields---can be
described with only two. The purpose of this short note is to point out the
almost obvious fact that the hierarchy described by the two bosons is not the
KP hierarchy but rather a reduction thereof---one which is moreover
incompatible with the reduction to the KdV-type subhierarchies.
|
hep-th/9207013
| 727,382 |
Constraints on the core temperature (T_c) of the Sun and on neutrino-
oscillation parameters are obtained from the existing solar neutrino data,
including the recent GALLEX and Kamiokande III results. (1) A purely
astrophysical solution to the solar neutrino problem is strongly disfavored by
the data: the best fit in a cooler Sun model requires an 8% reduction in T_c,
but the chi-sqaured test rejects this hypothesis at 99.99% C.L., suggesting new
neutrino physics. (2) Assuming the Standard Solar Model (SSM) and MSW
oscillations, the MSW parameters are constrained to two small regions: one in
the non-adiabatic region and the other in the large-mixing region. The
non-adiabatic solution gives a considerably better fit. For nu_e oscillations
into sterile neutrinos, the allowed region (90%) is constrained to non-
adiabatic oscillations. As long as the SSM is assumed, the neutrino mixing
angles are at least four times larger, or considerably smaller, than the
corresponding quark mixing angles. (3) Allowing both MSW oscillations and a
non-standard core temperature, a) the experiments determine the core
temperature at the 5% level, yielding a value consistent with the SSM
prediction. b) When T_c is used as a free parameter, the allowed MSW region is
broadened: a cooler Sun (T_c=0.95) allows mass and mixing implied by the SUSY
SO(10) GUT, while a warmer Sun (T_c=1.05) allows parameter space suggested by
intermediate-scale SO(10) GUTs. Superstring-inspired models are consistent with
all solutions. (4) From the narrowed parameter space, we predict the neutrino
spectral shape which should be observed in SNO. Throughout the calculation we
use the latest Bahcall-Pinsonneault SSM, and include nuclear and astrophysical
uncertainties in a simplified, but physically transparent way.
|
hep-ph/9207213
| 727,382 |
We present a selfconsistent method for treating nonperturbative effects in
inclusive nonleptonic and semileptonic decays of heavy flavour hadrons. These
effects give rise to powerlike corrections $\propto 1/m_Q^n\,$, $n \ge 2$ with
$m_Q$ denoting the heavy quark mass.The leading correction to the semileptonic
branching ratio occurs for n=2. It is expressed in terms of the
vector-pseudoscalar mass splitting: $\delta BR\ind{sl}/BR\ind{sl} \simeq
BR\ind{nl}\, \cdot \,6\,(\,(M_V^2-M_P^2)/m_Q^2)\cdot (c_+^2 - c_-^2)/2N_c$ and
yields a {\it reduction} of $BR\ind{sl}$. This nonperturbative correction
contributes to the nonleptonic width with a sign opposite to that of the
perturbative terms that are non-leading in $1/N_c$. In beauty decays the former
reduces the latter by 20 \% whereas in charm decays they more or less cancel.
This leads to a {\it reduction} of $BR\ind{sl}$ by no more than 10 \% in beauty
decays and by a factor of roughly two in charm decays. We confront these
results with those obtained from phenomenological models of heavy flavour
decays and find that such models are unable to mimic these leading corrections
by a specific choice of quark masses or by invoking Fermi motion.
|
hep-ph/9207214
| 727,383 |
Our work on models with Wilson--Yukawa couplings is reviewed. Conclusions
include the failure of such models to produce continuum chiral gauge theories.
|
hep-lat/9207004
| 727,383 |
We have studied the Eichten--Preskill proposal for constructing lattice
chiral gauge theories using both strong and weak coupling methods. The results
indicate that this proposal is unlikely to work due to a dynamical behavior
similar to that of the Smit--Swift proposal, which also does not give rise to
chiral fermions.
|
hep-lat/9207005
| 727,383 |
A convenient way to calculate $N$-particle quantum partition functions is by
confining the particles in a weak harmonic potential instead of using a finite
box or periodic boundary conditions. There is, however, a slightly different
connection between partition functions and thermodynamic quantities with such
volume regularization. This is made explicit, and its origin explained to be
due to the system having a space-varying density in an external potential.
Beyond perturbation theory there is a potential pitfall with the method, which
is pointed out.
|
cond-mat/9207005
| 727,383 |
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