37 research outputs found
Comments on Noncommutative Superspace
We study the N=1/2 supersymmetric theory on noncommutative superspace which
is a deformation of usual superspace. We consider deformed Wess-Zumino model as
an example and show vanishing of vacuum energy, renormalization of
superpotential and nonvanishing of tadpole. We find that the perturbative
effective action has terms which are not written in the star deformation. Also
we consider gauge theory on noncommutative superspace and observe that gauge
group is restricted. We generalize the star deformation to include
noncommutativity between bosonic coordinates and fermionic coordinates.Comment: 19 pages, 6 figures, JHEP class, footnotes added, typos corrected,
version to appear in JHE
Macroscopic strings as heavy quarks: Large-N gauge theory and anti-de Sitter supergravity
We study some aspects of Maldacena's large correspondence between N=4
superconformal gauge theory on D3-brane and maximal supergravity on AdS_5xS_5
by introducing macroscopic strings as heavy (anti)-quark probes. The
macroscopic strings are semi-infinite Type IIB strings ending on D3-brane
world-volume. We first study deformation and fluctuation of D3-brane when a
macroscopic BPS string is attached. We find that both dynamics and boundary
conditions agree with those for macroscopic string in anti-de Sitter
supergravity. As by-product we clarify how Polchinski's Dirichlet / Neumann
open string boundary conditions arise dynamically. We then study non-BPS
macroscopic string anti-string pair configuration as physical realization of
heavy quark Wilson loop. We obtain quark-antiquark static potential from the
supergravity side and find that the potential exhibits nonanalyticity of
square-root branch cut in `t Hooft coupling parameter. We put forward the
nonanalyticity as prediction for large-N gauge theory at strong `t Hooft
coupling limit. By turning on Ramond-Ramond zero-form potential, we also study
theta-vacuum angle dependence of the static potential. We finally discuss
possible dynamical realization of heavy N-prong string junction and of large-N
loop equation via local electric field and string recoil thereof. Throughout
comparisons of the AdS-CFT correspondence, we find crucial role played by
`geometric duality' between UV and IR scales on directions perpendicular to
D3-brane and parallel ones, explaining how AdS5 spacetime geometry emerges out
of four-dimensional gauge theory at strong coupling.Comment: Latex, 6 figures, v2. typos corrected, v3. published versio
Anatomy of One-Loop Effective Action in Noncommutative Scalar Field Theories
One-loop effective action of noncommutative scalar field theory with cubic
self-interaction is studied. Utilizing worldline formulation, both planar and
nonplanar part of the effective action are computed explicitly. We find
complete agreement of the result with Seiberg-Witten limit of string worldsheet
computation and standard Feynman diagrammatics. We prove that, at low-energy
and large noncommutativity limit, nonplanar part of the effective action is
simplified enormously and is resummable into a quadratic action of scalar open
Wilson line operators.Comment: 26 pages, Latex, 4 eps figures, v2. typos corrected, v3.
combinatorics correcte
Wilson-Polyakov Loop at Finite Temperature in Large N Gauge Theory and Anti-de Sitter Supergravity
Aspects of d=4, N=4 superconformal U(N) gauge theory are studied at finite
temperature. Utilizing dual description of large and strong coupling limit
via Type IIB string theory compactification on Schwarzschild anti-de Sitter
spacetime, we study correlations of Wilson-Polyakov loops and heavy quark
potential thereof. We find that the heavy quark potential is Coulomb-like and
has a finite range, as expected for gauge theory in high temperature,
deconfinement phase. The potential exhibits finite temperature scaling
consistent with underlying conformal invariance. We also study isolated heavy
quark on probe D3-brane world-volume and find supporting evidence that near
extremal D3-branes are located at Schwarzschild horizon.Comment: Latex, 17 pages, four figures, substantial revisio
BPS Dynamics of Triple (p,q) String Junction
We study dynamics of triple junction of (p,q) strings in Type IIB string
theory. We probe tension and mass density of (p,q) strings by studying harmonic
fluctuations of the triple junction. We show that they agree perfectly with BPS
formula provided suitable geometric interpretation of the junction is given. We
provide a precise statement of BPS limit and force-balance property. At weak
coupling and sufficiently dense limit, we argue that (p,q)-string embedded in
string network is a `wiggly string', whose low-energy dynamics can be described
via renormalization group evolved, smooth effective non-relativistic string. We
also suggest the possibility that, upon Type IIB strings are promoted to
M-theory membrane, there can exist `evanescent' bound-states at triple junction
in the continuum.Comment: 11 pages, Latex, 3 figures, typos correcte
Instantons of M(atrix) Theory in PP-Wave Background
M(atrix) theory in PP-wave background possesses a discrete set of classical
vacua, all of which preserves 16 supersymmetry and interpretable as collection
of giant gravitons. We find Euclidean instanton solutions that interpolate
between them, and analyze their properties. Supersymmetry prevents direct
mixing between different vacua but still allows effect of instanton to show up
in higher order effective interactions, such as analog of v^4 interaction of
flat space effective theory. An explicit construction of zero modes is
performed, and Goldstone zero modes, bosonic and fermionic, are identified. We
further generalize this to massive M(atrix) theory that includes fundamental
hypermultiplets, corresponding to insertion of longitudinal fivebranes in the
background. After a brief comparison to their counterpart in AdS\times S, we
close with a summary.Comment: 25 pages, LaTeX, references added, section 5 update
Thermodynamics of AdS/QCD
We study finite temperature properties of four dimensional QCD-like gauge
theories in the gauge theory/gravity duality picture. The gravity dual contains
two deformed 5d AdS metrics, with and without a black hole, and a dilaton. We
study the thermodynamics of the 4d boundary theory and constrain the two
metrics so that they correspond to a high and a low temperature phase separated
by a first order phase transition. The equation of state has the standard form
for the pressure of a strongly coupled fluid modified by a vacuum energy, a bag
constant. We determine the parameters of the deformation by using QCD results
for and the hadron spectrum. With these parameters, we show that the
phase transition in the 4d boundary theory and the 5d bulk Hawking-Page
transition agree. We probe the dynamics of the two phases by computing the
quark-antiquark free energy in them and confirm that the transition corresponds
to confinement-deconfinement transition.Comment: 1+19 pages, 6 figures, references added, section 3 improve
Supersymmetry and Branes in M-theory Plane-waves
We study brane embeddings in M-theory plane-waves and their supersymmetry.
The relation with branes in AdS backgrounds via the Penrose limit is also
explored. Longitudinal planar branes are originated from AdS branes while giant
gravitons of AdS spaces become spherical branes which are realized as fuzzy
spheres in the massive matrix theory.Comment: 17 pages, JHEP style, references added, typos correcte
Open Wilson Lines and Generalized Star Product in Noncommutative Scalar Field Theories
Open Wilson line operators and generalized star product have been studied
extensively in noncommutative gauge theories. We show that they also show up in
noncommutative scalar field theories as universal structures. We first point
out that dipole picture of noncommutative geometry provides an intuitive
argument for robustness of the open Wilson lines and generalized star products
therein. We calculate one-loop effective action of noncommutative scalar field
theory with cubic self-interaction and show explicitly that the generalized
star products arise in the nonplanar part. It is shown that, at low-energy,
large noncommutativity limit, the nonplanar part is expressible solely in terms
of the {\sl scalar} open Wilson line operator and descendants.Comment: 13 pages, Latex, 1 .eps figure, v2. typos corrected, v3.
combinatorics correcte
Detection of SARS-associated Coronavirus in Throat Wash and Saliva in Early Diagnosis
Early detection of SARS-CoV in throat wash and saliva suggests that these specimens are ideal for SARS diagnosis