634 research outputs found
Complete N=4 Structure of Low-Energy Effective Action in N=4 Super Yang-Mills Theories
Using the superfield approach, we construct full
supersymmetric low-energy effective actions for SYM models, with
both gauge superfield strengths and hypermultiplet superfields
included. The basic idea is to complete the known non-holomorphic effective
potentials which depend only on superfield strengths and
to the full on-shell invariants by adding the
appropriate superfield hypermultiplet terms. We prove that the effective
potentials of the form can be completed in
this way and present the precise structure of the corresponding completions.
However, the effective potentials of the non-logarithmic form suggested in
hep-th/9811017 and hep-th/9909020 do not admit the completion.
Therefore, such potentials cannot come out as (perturbative or
non-perturbative) quantum corrections in SYM models.Comment: 14 pages, Latex, no figures, slight corrections, refs adde
Renormalization group improved gravitational actions: a Brans-Dicke approach
A new framework for exploiting information about the renormalization group
(RG) behavior of gravity in a dynamical context is discussed. The
Einstein-Hilbert action is RG-improved by replacing Newton's constant and the
cosmological constant by scalar functions in the corresponding Lagrangian
density. The position dependence of and is governed by a RG
equation together with an appropriate identification of RG scales with points
in spacetime. The dynamics of the fields and does not admit a
Lagrangian description in general. Within the Lagrangian formalism for the
gravitational field they have the status of externally prescribed
``background'' fields. The metric satisfies an effective Einstein equation
similar to that of Brans-Dicke theory. Its consistency imposes severe
constraints on allowed backgrounds. In the new RG-framework, and
carry energy and momentum. It is tested in the setting of homogeneous-isotropic
cosmology and is compared to alternative approaches where the fields and
do not carry gravitating 4-momentum. The fixed point regime of the
underlying RG flow is studied in detail.Comment: LaTeX, 72 pages, no figure
Density functional study of Au (n=2-20) clusters: lowest-energy structures and electronic properties
We have investigated the lowest-energy structures and electronic properties
of the Au(n=2-20) clusters based on density functional theory (DFT) with
local density approximation. The small Au clusters adopt planar structures
up to n=6. Tabular cage structures are preferred in the range of n=10-14 and a
structural transition from tabular cage-like structure to compact
near-spherical structure is found around n=15. The most stable configurations
obtained for Au and Au clusters are amorphous instead of
icosahedral or fcc-like, while the electronic density of states sensitively
depend on the cluster geometry. Dramatic odd-even alternative behaviors are
obtained in the relative stability, HOMO-LUMO gaps and ionization potentials of
gold clusters. The size evolution of electronic properties is discussed and the
theoretical ionization potentials of Au clusters compare well with
experiments.Comment: 6 pages, 7 figure
Two-loop N=4 Super Yang Mills effective action and interaction between D3-branes
We compute the leading low-energy term in the planar part of the 2-loop
contribution to the effective action of SYM theory in 4 dimensions,
assuming that the gauge group is broken to by a
constant scalar background . While the leading 1-loop correction is the
familiar term, the 2-loop expression starts with . The 1-loop constant is known to be equal to the coefficient
of the term in the Born-Infeld action for a probe D3-brane separated by
distance from a large number of coincident D3-branes. We show that
the same is true also for the 2-loop constant : it matches the coefficient
of the term in the D3-brane probe action. In the context of the AdS/CFT
correspondence, this agreement suggests a non-renormalization of the
coefficient of the term beyond two loops. Thus the result of
hep-th/9706072 about the agreement between the term in the D0-brane
supergravity interaction potential and the corresponding 2-loop term in the 1+0
dimensional reduction of SYM theory has indeed a direct generalization
to 1+3 dimensions, as conjectured earlier in hep-th/9709087. We also discuss
the issue of gauge theory -- supergravity correspondence for higher order
(, etc.) terms.Comment: 33 pages, late
Lattice gluodynamics computation of Landau-gauge Green's functions in the deep infrared
We present recent results for the Landau-gauge gluon and ghost propagators in
SU(3) lattice gluodynamics obtained on a sequence of lattices with linear
extension ranging from L=64 to L=96 at , thus reaching "deep
infrared" momenta down to 75 MeV. Our gauge-fixing procedure essentially uses a
simulated annealing technique which allows us to reach gauge-functional values
closer to the global maxima than standard approaches do. Our results are
consistent with the so-called decoupling solutions found for Dyson-Schwinger
and functional renormalization group equations.Comment: 6 pages, 5 figures. References added, minor changes to match
published versio
Strong-coupling study of the Gribov ambiguity in lattice Landau gauge
We study the strong-coupling limit beta=0 of lattice SU(2) Landau gauge
Yang-Mills theory. In this limit the lattice spacing is infinite, and thus all
momenta in physical units are infinitesimally small. Hence, the infrared
behavior can be assessed at sufficiently large lattice momenta. Our results
show that at the lattice volumes used here, the Gribov ambiguity has an
enormous effect on the ghost propagator in all dimensions. This underlines the
severity of the Gribov problem and calls for refined studies also at finite
beta. In turn, the gluon propagator only mildly depends on the Gribov
ambiguity.Comment: 14 pages, 22 figures; minor changes, matches version to appear in
Eur. Phys. J.
Superfield theory and supermatrix model
We study the noncommutative superspace of arbitrary dimensions in a
systematic way. Superfield theories on a noncommutative superspace can be
formulated in two folds, through the star product formalism and in terms of the
supermatrices. We elaborate the duality between them by constructing the
isomorphism explicitly and relating the superspace integrations of the star
product Lagrangian or the superpotential to the traces of the supermatrices. We
show there exists an interesting fine tuned commutative limit where the duality
can be still maintained. Namely on the commutative superspace too, there exists
a supermatrix model description for the superfield theory. We interpret the
result in the context of the wave particle duality. The dual particles for the
superfields in even and odd spacetime dimensions are D-instantons and D0-branes
respectively to be consistent with the T-duality.Comment: 1+16 pages, no figure; expanded version, references added; Convention
for Clifford algebra improve
Curvature Dependence of Running Gauge Coupling and Confinement in AdS/CFT Correspondence
We construct IIB supergravity (viewed as dilatonic gravity) background with
non-trivial dilaton and with curved four-dimensional space. Such a background
may describe another vacuum of maximally supersymmetric Yang-Mills theory or
strong coupling regime of (non)-supersymmetric gauge theory with (power-like)
running gauge coupling which depends on curvature. Curvature dependent
quark-antiquark potential is calculated where the geometry type of hyperbolic
(or de Sitter universe) shows (or not) the tendency of the confinement.
Generalization of IIB supergravity background with non-constant axion is
presented. Quark-antiquark potential being again curvature-dependent has a
possibility to produce the standard area law for large separations.Comment: LaTeX file, 24 pages, presentation is improve
Infrared exponents and the strong-coupling limit in lattice Landau gauge
We study the gluon and ghost propagators of lattice Landau gauge in the
strong-coupling limit beta=0 in pure SU(2) lattice gauge theory to find
evidence of the conformal infrared behavior of these propagators as predicted
by a variety of functional continuum methods for asymptotically small momenta
. In the strong-coupling limit, this same
behavior is obtained for the larger values of a^2q^2 (in units of the lattice
spacing a), where it is otherwise swamped by the gauge field dynamics.
Deviations for a^2q^2 < 1 are well parameterized by a transverse gluon mass
. Perhaps unexpectedly, these deviations are thus no finite-volume
effect but persist in the infinite-volume limit. They furthermore depend on the
definition of gauge fields on the lattice, while the asymptotic conformal
behavior does not. We also comment on a misinterpretation of our results by
Cucchieri and Mendes in Phys. Rev. D81 (2010) 016005.Comment: 17 pages, 12 figures. Revised version (mainly sections I and II);
references and comments on subsequent work on the subject added
Gauge invariant Lagrangian construction for massive bosonic higher spin fields in D dimentions
We develop the BRST approach to Lagrangian formulation for massive higher
integer spin fields on a flat space-time of arbitrary dimension. General
procedure of gauge invariant Lagrangian construction describing the dynamics of
massive bosonic field with any spin is given. No off-shell constraints on the
fields (like tracelessness) and the gauge parameters are imposed. The procedure
is based on construction of new representation for the closed algebra generated
by the constraints defining an irreducible massive bosonic representation of
the Poincare group. We also construct Lagrangian describing propagation of all
massive bosonic fields simultaneously. As an example of the general procedure,
we derive the Lagrangians for spin-1, spin-2 and spin-3 fields containing total
set of auxiliary fields and gauge symmetries of free massive bosonic higher
spin field theory.Comment: 27 page
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