553 research outputs found
Hysteresis in Anti-Ferromagnetic Random-Field Ising Model at Zero Temperature
We study hysteresis in anti-ferromagnetic random-field Ising model at zero
temperature. The external field is cycled adiabatically between - and
. Two different distributions of the random-field are considered, (i) a
uniform distribution of width centered at the origin, and (ii) a
Gaussian distribution with average value zero and standard deviation .
In each case the hysteresis loop is determined exactly in one dimension and
compared with numerical simulations of the model
Loop Equations as a Generalized Virasoro Constraints
The loop equations in the lattice gauge theory are represented in the
form of constraints imposed on a generating functional for the Wilson loop
correlators. These constraints form a closed algebra with respect to
commutation. This algebra generalizes the Virasoro one, which is known to
appear in one-matrix models in the same way. The realization of this algebra in
terms of the infinitesimal changes of generators of the loop space is given.
The representations on the tensor fields on the loop space, generalizing the
integer spin conformal fields, are constructed. The structure constants of the
algebra under consideration being independent of the coupling constants, almost
all the results are valid in the continuum.Comment: 7 pages, LaTex (3 LaTex figures), SMI-94-
Supermatrix models and multi ZZ-brane partition functions in minimal superstring theories
We study (p,q)=(2,4k) minimal superstrings within the minimal superstring
field theory constructed in hep-th/0611045. We explicitly give a solution to
the W_{1+\infty} constraints by using charged D-instanton operators, and show
that the (m,n)-instanton sector with m positive-charged and n negative-charged
ZZ-branes is described by an (m+n)\times (m+n) supermatrix model. We argue that
the supermatrix model can be regarded as an open string field theory on the
multi ZZ-brane system.Comment: 15 pages, 1 figure, minor chang
Interaction of massless Dirac field with a Poincar\'e gauge field
In this paper we consider a model of Poincar\'e gauge theory (PGT) in which a
translational gauge field and a Lorentz gauge field are actually identified
with the Einstein's gravitational field and a pair of ``Yang-Mills'' field and
its partner, respectively.In this model we re-derive some special solutions and
take up one of them. The solution represents a ``Yang-Mills'' field without its
partner field and the Reissner-Nordstr\"om type spacetime, which are generated
by a PGT-gauge charge and its mass.It is main purpose of this paper to
investigate the interaction of massless Dirac fields with those fields. As a
result, we find an interesting fact that the left-handed massless Dirac fields
behave in the different manner from the right-handed ones. This can be
explained as to be caused by the direct interaction of Dirac fields with the
``Yang-Mills'' field. Accordingly, the phenomenon can not happen in the
behavior of the neutrino waves in ordinary Reissner-Nordstr\"om geometry. The
difference between left- and right-handed effects is calculated quantitatively,
considering the scattering problems of the massless Dirac fields by our
Reissner-Nordstr\"om type black-hole.Comment: 10pages, RevTeX3.
On the validity of ADM formulation in 2D quantum gravity
We investigate 2d gravity quantized in the ADM formulation, where only the
loop length is retained as a dynamical variable of the gravitation, in
order to get an intuitive physical insight of the theory. The effective action
of is calculated by adding scalar fields of conformal coupling, and the
problems of the critical dimension and the time development of are
addressed.Comment: 12 page
Electron cloud studies for KEKB
Electron-cloud build up, incoherent tune spread and electron-induced beam instability are likely to be responsible for the vertical beam-size increase observed at the KEKB Low Energy Ring (LER). We report on recent simulations and analytical estimated, a ddressing the electron-cloud evolution for various magnet configurations, computing the beam size blow up predicted by three different simulation models (micro-bunches, multiparticle tracking with soft Gaussian approximation, particle-in cell) and finally discussing analytical expressions for the instability threshold
Non-linear Structures in Non-critical NSR String
We investigate the Ward identities of the \W_{\infty} symmetry in the
super-Liouville theory coupled to the super-conformal matter of central charge
. The theory is classified into two chiralities.
For the positive chirality, all gravitationally dressed scaling operators are
generated from the gravitational primaries by acting one of the ring
generators in the R-sector on them repeatedly. After fixing the normalizations
of the dressed scaling operators, we find that the Ward identities are
expressed in the form of the {\it usual} \W_q algebra constraints as in the
bosonic case: \W^{(k+1)}_n \tau =0, , where the equations for even and odd come from the currents in the
NS- and the R-sector respectively. The non-linear terms come from the anomalous
contributions at the boundaries of moduli space. The negative chirality is
defined by interchanging the roles of and . Then we get the \W_p
algebra constraints.Comment: 22 pages, Latex file, YITP/U-94-16, UT-Komaba/94-1
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