1,221 research outputs found

### Grand-canonical simulation of two-dimensional simplicial gravity

The string susceptibility exponents of dynamically triangulated 2-dimensional
surfaces with various topologies, such as a sphere, torus and double-torus,
were calculated by the grand-canonical Monte Carlo method. These simulations
were made for surfaces coupled to $d$-Ising spins ($d$=0,1,2,3,5). In each
simulation the area of surface was constrained to within 1000 to 3000 of
triangles, while maintaining the detailed-balance condition. The numerical
results show excellent agreement with theoretical predictions as long as $d
\leq 2$.Comment: 9 pages, Latex include 5 postscript figures, using psfig.sty and
cite.st

### Minbu distribution of two dimensional quantum gravity: simulation result and semiclassical analysis

We analyse MINBU distribution of 2 dimensional quantum gravity. New data of R^2-gravity by the Monte Carlo simulation and its theoretical analysis by the semiclassical approach are presented. The cross-over phenomenon takes place at some size of the baby universe where the randomness competes with the smoothing force of R^2-term. The dependence on the central charge c_m\ and on the R^2-coupling are explained for the ordinary 2d quantum gravity and for R^2-gravity. The R^2-Liouville solution plays the central role in the semiclassical analysis. A total derivative term (surface term) and the infrared regularization play important roles . The surface topology is that of a sphere

### Geometry of 4d Simplicial Quantum Gravity with a U(1) Gauge Field

The geometry of 4D simplicial quantum gravity with a U(1) gauge field is
studied numerically. The phase diagram shows a continuous transition when
gravity is coupled with a U(1) gauge field. At the critical point measurements
of the curvature distribution of S^4 space shows an inflated geometry with
homogeneous and symmetric nature. Also, by choosing a 4-simplex and fixing the
scalar curvature geometry of the space is measured.Comment: 3 pages, 2 eps figure. Talked at Lattice 2000 (Gravity

### Scaling Behavior in 4D Simplicial Quantum Gravity

Scaling relations in four-dimensional simplicial quantum gravity are proposed
using the concept of the geodesic distance. Based on the analogy of a loop
length distribution in the two-dimensional case, the scaling relations of the
boundary volume distribution in four dimensions are discussed in three regions:
the strong-coupling phase, the critical point and the weak-coupling phase. In
each phase a different scaling behavior is found.Comment: 12 pages, latex, 10 postscript figures, uses psfig.sty and cite.st

### Introducing Dynamical Triangulations to the Type IIB Superstrings

In order to consider non-perturbative effects of superstrings, we try to
apply dynamical triangulations to the type IIB superstrings. The discretized
action is constructed from the type IIB matrix model proposed as a constructive
definition of superstring theory. The action has the local N=2 supersymmetry
explicitly, and has no extra fermionic degrees of freedom. We evaluate the
partition function for some simple configurations and discuss constraints
required from the finiteness of partition functions.Comment: LATTICE99, 3 pages, LaTeX with 2 figures, espcrc2.st

### Hadron-hadron interaction from SU(2) lattice QCD

We evaluate interhadron interactions in two-color lattice QCD from
Bethe-Salpeter amplitudes on the Euclidean lattice. The simulations are
performed in quenched SU(2) QCD with the plaquette gauge action at $\beta =
2.45$ and the Wilson quark action. We concentrate on S-wave scattering states
of two scalar diquarks. Evaluating different flavor combinations with various
quark masses, we try to find out the ingredients in hadronic interactions.
Between two scalar diquarks ($u C\gamma_5 d$, the lightest baryon in SU(2)
system), we observe repulsion in short-range region, even though present quark
masses are not very light. We define and evaluate the "quark-exchange part" in
the interaction, which is induced by adding quark-exchange diagrams, or
equivalently, by introducing Pauli blocking among some of quarks. The repulsive
force in short-distance region arises only from the "quark-exchange part", and
disappears when quark-exchange diagrams are omitted. We find that the strength
of repulsion grows in light quark-mass regime and its quark-mass dependence is
similar to or slightly stronger than that of the color-magnetic interaction by
one-gluon-exchange (OGE) processes. It is qualitatively consistent with the
constituent-quark model picture that a color-magnetic interaction among quarks
is the origin of repulsion. We also find a universal long-range attractive
force, which enters in any flavor channels of two scalar diquarks and whose
interaction range and strength are quark-mass independent. The weak quark-mass
dependence of interaction ranges in each component implies that meson-exchange
contributions are small and subdominant, and the other contributions, {\it ex.}
flavor exchange processes, color-Coulomb or color-magnetic interactions, are
considered to be predominant, in the quark-mass range we evaluated.Comment: 14 pages, 20 figure

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