1,552 research outputs found
Simplicial Chiral Models
Principal chiral models on a d-1 dimensional simplex are introduced and
studied analytically in the large limit. The and
models are explicitly solved. Relationship with standard lattice models and
with few-matrix systems in the double scaling limit are discussed.Comment: 6 pages, PHYZZ
Survival probability of large rapidity gaps in QCD and N=4 SYM motivated model
In this paper we present a self consistent theoretical approach for the
calculation of the Survival Probability for central dijet production . These
calculations are performed in a model of high energy soft interactions based on
two ingredients:(i) the results of N=4 SYM, which at the moment is the only
theory that is able to deal with a large coupling constant; and (ii) the
required matching with high energy QCD. Assuming, in accordance with these
prerequisites, that soft Pomeron intercept is rather large and the slope of the
Pomeron trajectory is equal to zero, we derive analytical formulae that sum
both enhanced and semi-enhanced diagrams for elastic and diffractive
amplitudes. Using parameters obtained from a fit to the available experimental
data, we calculate the Survival Probability for central dijet production at
energies accessible at the LHC. The results presented here which include the
contribution of semi-enhanced and net diagrams, are considerably larger than
our previous estimates.Comment: 11 pages, 10 pictures in .eps file
Lessons from : Vacuum structure, Asymptotic Series, Instantons and all that
We discuss two dimensional with fermions in the
fundamental as well as adjoint representation. We find factorial growth in the coefficients of
the large order perturbative expansion. We argue that this behavior is related
to classical solutions of the theory, instantons, thus it has nonperturbative
origin. Phenomenologically such a growth is related to highly excited states in
the spectrum. We also analyze the heavy-light quark system within
operator product expansion (which it turns out to be an asymptotic series).
Some vacuum condensates \la\bar{q}(x_{\mu}D_{\mu})^{2n}q\ra\sim (x^2)^n\cdot
n! which are responsible for this factorial growth are also discussed. We
formulate some general puzzles which are not specific for 2D physics, but are
inevitable features of any asymptotic expansion. We resolve these apparent
puzzles within and we speculate that analogous puzzles might occur in
real 4-dimensional QCD as well.Comment: latex, 26 pages. A final version to appear in Phys. Rev.
Strong coupling expansion of chiral models
A general precedure is outlined for an algorithmic implementation of the
strong coupling expansion of lattice chiral models on arbitrary lattices. A
symbolic character expansion in terms of connected values of group integrals on
skeleton diagrams may be obtained by a fully computerized approach.Comment: 2 pages, PostScript file, contribution to conference LATTICE '9
High Energy Bounds on Soft N=4 SYM Amplitudes from AdS/CFT
Using the AdS/CFT correspondence, we study the high-energy behavior of
colorless dipole elastic scattering amplitudes in N=4 SYM gauge theory through
the Wilson loop correlator formalism and Euclidean to Minkowskian analytic
continuation. The purely elastic behavior obtained at large impact-parameter L,
through duality from disconnected AdS_5 minimal surfaces beyond the
Gross-Ooguri transition point, is combined with unitarity and analyticity
constraints in the central region. In this way we obtain an absolute bound on
the high-energy behavior of the forward scattering amplitude due to the
graviton interaction between minimal surfaces in the bulk. The dominant
"Pomeron" intercept is bounded by alpha less than or equal to 11/7 using the
AdS/CFT constraint of a weak gravitational field in the bulk. Assuming the
elastic eikonal approximation in a larger impact-parameter range gives alpha
between 4/3 and 11/7. The actual intercept becomes 4/3 if one assumes the
elastic eikonal approximation within its maximally allowed range L larger than
exp{Y/3}, where Y is the total rapidity. Subleading AdS/CFT contributions at
large impact-parameter due to the other d=10 supergravity fields are obtained.
A divergence in the real part of the tachyonic KK scalar is cured by
analyticity but signals the need for a theoretical completion of the AdS/CFT
scheme.Comment: 25 pages, 3 eps figure
Surface Tension at Finite Tempearture in the MIT Bag Model
At the surface tension in the MIT bag model for a
single hadron is known to be negligible as compared to the bag pressure . We show that at finite temperature it has a substantial value of 50 -
70 MeV which also differ from hadron to hadron. We also find that the dynamics
of the Quark-Gluon Plasma is such that the creation of hybrids
with massive quarks will predominate over the creation of
mesons.Comment: Substantial changes in the revised version and a new author included,
13 pages in Latex and one figur
Duality and replicas for a unitary matrix model
In a generalized Airy matrix model, a power replaces the cubic term of
the Airy model introduced by Kontsevich. The parameter corresponds to
Witten's spin index in the theory of intersection numbers of moduli space of
curves. A continuation in down to yields a well studied unitary
matrix model, which exhibits two different phases in the weak and strong
coupling regions, with a third order critical point in-between. The application
of duality and replica to the -th Airy model allows one to recover both the
weak and strong phases of the unitary model, and to establish some new results
for these expansions. Therefore the unitary model is also indirectly a
generating function for intersection numbers.Comment: 18 page, add referece
Parity Effects in Eigenvalue Correlators, Parametric and Crossover Correlators in Random Matrix Models: Application to Mesoscopic systems
This paper summarizes some work I've been doing on eigenvalue correlators of
Random Matrix Models which show some interesting behaviour. First we consider
matrix models with gaps in there spectrum or density of eigenvalues. The
density-density correlators of these models depend on whether N, where N is the
size of the matrix, takes even or odd values. The fact that this dependence
persists in the large N thermodynamic limit is an unusual property and may have
consequences in the study of one electron effects in mesoscopic systems.
Secondly, we study the parametric and cross correlators of the Harish
Chandra-Itzykson-Zuber matrix model. The analytic expressions determine how the
correlators change as a parameter (e.g. the strength of a perturbation in the
hamiltonian of the chaotic system or external magnetic field on a sample of
material) is varied. The results are relevant for the conductance fluctuations
in disordered mesoscopic systems.Comment: 12 pages, Latex, 2 Figure
Effective Lagrangian for strongly coupled domain wall fermions
We derive the effective Lagrangian for mesons in lattice gauge theory with
domain-wall fermions in the strong-coupling and large-N_c limits. We use the
formalism of supergroups to deal with the Pauli-Villars fields, needed to
regulate the contributions of the heavy fermions. We calculate the spectrum of
pseudo-Goldstone bosons and show that domain wall fermions are doubled and
massive in this regime. Since we take the extent and lattice spacing of the
fifth dimension to infinity and zero respectively, our conclusions apply also
to overlap fermions.Comment: 26 pp. RevTeX and 3 figures; corrected error in symmetry breaking
scheme and added comments to discussio
Glueball masses in the large N limit
The lowest-lying glueball masses are computed in SU() gauge theory on a
spacetime lattice for constant value of the lattice spacing and for
ranging from 3 to 8. The lattice spacing is fixed using the deconfinement
temperature at temporal extension of the lattice . The calculation is
conducted employing in each channel a variational ansatz performed on a large
basis of operators that includes also torelon and (for the lightest states)
scattering trial functions. This basis is constructed using an automatic
algorithm that allows us to build operators of any size and shape in any
irreducible representation of the cubic group. A good signal is extracted for
the ground state and the first excitation in several symmetry channels. It is
shown that all the observed states are well described by their large
values, with modest corrections. In addition spurious states
are identified that couple to torelon and scattering operators. As a byproduct
of our calculation, the critical couplings for the deconfinement phase
transition for N=5 and N=7 and temporal extension of the lattice are
determined.Comment: 1+36 pages, 22 tables, 21 figures. Typos corrected, conclusions
unchanged, matches the published versio
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