99 research outputs found
Numerical evidence for the Maldacena conjecture in two-dimensional N=(8,8) super Yang-Mills theory
The N=(8,8) super Yang-Mills theory in 1+1 dimensions is solved at strong
coupling to directly confirm the predictions of supergravity at weak coupling.
The calculations are done in the large-N_c approximation using Supersymmetric
Discrete Light-Cone Quantization. The stress-energy correlator is obtained as a
function of the separation r; for intermediate values of r, the correlator
behaves in a manner consistent with the 1/r^5 behavior predicted by
weak-coupling supergravity.Comment: 6 pages, 3 figures; requires espcrc2.sty; to appear in the
proceedings of the Workshop on Light-Cone QCD and Nonperturbative Hadron
Physics, Cairns, Australia, July 7-15, 200
Anomalously light states in super-Yang-Mills Chern-Simons theory
Inspired by our previous finding that supersymmetric Yang-Mills-Chern-Simons
(SYM-CS) theory dimensionally reduced to 1+1 dimensions possesses approximate
Bogomol'nyi-Prasad-Sommerfield (BPS) states, we study the analogous phenomenon
in the three-dimensional theory. Approximate BPS states in two dimensions have
masses which are nearly independent of the Yang-Mills coupling and proportional
to their average number of partons. These states are a reflection of the
exactly massless BPS states of the underlying pure SYM theory. In three
dimensions we find that this mechanism leads to anomalously light bound states.
While the mass scale is still proportional to the average number of partons
times the square of the CS coupling, the average number of partons in these
bound states changes with the Yang-Mills coupling. Therefore, the masses of
these states are not independent of the coupling. Our numerical calculations
are done using supersymmetric discrete light-cone quantization (SDLCQ).Comment: 14 pages, 3 figures, LaTe
Simulation of Dimensionally Reduced SYM-Chern-Simons Theory
A supersymmetric formulation of a three-dimensional SYM-Chern-Simons theory
using light-cone quantization is presented, and the supercharges are calculated
in light-cone gauge. The theory is dimensionally reduced by requiring all
fields to be independent of the transverse dimension. The result is a
non-trivial two-dimensional supersymmetric theory with an adjoint scalar and an
adjoint fermion. We perform a numerical simulation of this SYM-Chern-Simons
theory in 1+1 dimensions using SDLCQ (Supersymmetric Discrete Light-Cone
Quantization). We find that the character of the bound states of this theory is
very different from previously considered two-dimensional supersymmetric gauge
theories. The low-energy bound states of this theory are very ``QCD-like.'' The
wave functions of some of the low mass states have a striking valence
structure. We present the valence and sea parton structure functions of these
states. In addition, we identify BPS-like states which are almost independent
of the coupling. Their masses are proportional to their parton number in the
large-coupling limit.Comment: 18pp. 7 figures, uses REVTe
Improved results for N=(2,2) super Yang-Mills theory using supersymmetric discrete light-cone quantization
We consider the (1+1)-dimensional super Yang--Mills theory
which is obtained by dimensionally reducing super Yang--Mills
theory in four dimension to two dimensions. We do our calculations in the
large- approximation using Supersymmetric Discrete Light Cone
Quantization. The objective is to calculate quantities that might be
investigated by researchers using other numerical methods. We present a
precision study of the low-mass spectrum and the stress-energy correlator
. We find that the mass gap of this theory closes as the
numerical resolution goes to infinity and that the correlator in the
intermediate region behaves like .Comment: 18 pages, 8 figure
Anti-Periodic Boundary Conditions in Supersymmetric DLCQ
It is of considerable importance to have a numerical method for solving
supersymmetric theories that can support a non-zero central charge. The central
charge in supersymmetric theories is in general a boundary integral and
therefore vanishes when one uses periodic boundary conditions. One is therefore
prevented from studying BPS states in the standard supersymmetric formulation
of DLCQ (SDLCQ). We present a novel formulation of SDLCQ where the fields
satisfy anti-periodic boundary conditions. The Hamiltonian is written as the
anti-commutator of two charges, as in SDLCQ. The anti-periodic SDLCQ we
consider breaks supersymmetry at finite resolution, but requires no
renormalization and becomes supersymmetric in the continuum limit. In
principle, this method could be used to study BPS states. However, we find its
convergence to be disappointingly slow.Comment: 9pp, 2 figure
Properties of the Bound States of Super-Yang-Mills-Chern-Simons Theory
We apply supersymmetric discrete light-cone quantization (SDLCQ) to the study
of supersymmetric Yang-Mills-Chern-Simons (SYM-CS) theory on R x S^1 x S^1. One
of the compact directions is chosen to be light-like and the other to be
space-like. Since the SDLCQ regularization explicitly preserves supersymmetry,
this theory is totally finite, and thus we can solve for bound-state wave
functions and masses numerically without renormalizing. The Chern-Simons term
is introduced here to provide masses for the particles while remaining totally
within a supersymmetric context. We examine the free, weak and strong-coupling
spectrum. The transverse direction is discussed as a model for universal extra
dimensions in the gauge sector. The wave functions are used to calculate the
structure functions of the lowest mass states. We discuss the properties of
Kaluza-Klein states and focus on how they appear at strong coupling. We also
discuss a set of anomalously light states which are reflections of the exact
Bogomol'nyi-Prasad-Sommerfield states of the underlying SYM theory.Comment: 20pp., 21 figure
Hippocampal Insulin Signaling And Neuroprotection Mediated By Physical Exercise In Alzheimeŕs Disease
Epidemiological studies indicate continuous increases in the prevalence of Alzheimer's Disease (AD) in the next few decades. The key feature of this disease is hippocampal neurodegeneration. This structure has an important role in learning and memory. Intense research efforts have sought to elucidate neuroprotective mechanisms responsible for hippocampal integrity. Insulin signaling seems to be a very promising pathway for the prevention and treatment of AD. This hormone has been described as a powerful activator of neuronal survival. Recent research showed that reduced insulin sensitivity leads to low-grade inflammation, and both phenomena are closely related to AD genesis. Concomitantly, exercise has been shown to exert anti-inflammatory effects and to promote improvement in insulin signaling in the hippocampus, which supports neuronal survival and constitutes an interesting non-pharmacological alternative for the prevention and treatment of AD. This review examines recent advances in understanding the molecular mechanisms involved in hippocampal neuroprotection mediated by exercise.2
Application of Pauli-Villars regularization and discretized light-cone quantization to a single-fermion truncation of Yukawa theory
We apply Pauli-Villars regularization and discretized light-cone quantization
to the nonperturbative solution of (3+1)-dimensional Yukawa theory in a
single-fermion truncation. Three heavy scalars, including two with negative
norm, are used to regulate the theory. The matrix eigenvalue problem is solved
for the lowest-mass state with use of a new, indefinite-metric Lanczos
algorithm. Various observables are extracted from the wave functions, including
average multiplicities and average momenta of constituents, structure
functions, and a form factor slope.Comment: 21 pages, 7 figures, RevTeX; published version: more extensive data
in the tables of v
Wave functions and properties of massive states in three-dimensional supersymmetric Yang-Mills theory
We apply supersymmetric discrete light-cone quantization (SDLCQ) to the study
of supersymmetric Yang-Mills theory on R x S^1 x S^1. One of the compact
directions is chosen to be light-like and the other to be space-like. Since the
SDLCQ regularization explicitly preserves supersymmetry, this theory is totally
finite, and thus we can solve for bound-state wave functions and masses
numerically without renormalizing. We present an overview of all the massive
states of this theory, and we see that the spectrum divides into two distinct
and disjoint sectors. In one sector the SDLCQ approximation is only valid up to
intermediate coupling. There we find a well defined and well behaved set of
states, and we present a detailed analysis of these states and their
properties. In the other sector, which contains a completely different set of
states, we present a much more limited analysis for strong coupling only. We
find that, while these state have a well defined spectrum, their masses grow
with the transverse momentum cutoff. We present an overview of these states and
their properties.Comment: RevTeX, 25 pages, 16 figure
Hypothalamic Endoplasmic Reticulum Stress Of Overtrained Mice After Recovery
knowing the relationship between endoplasmic reticulum (ER) stress and inflammation and based on the fact that downhill running-based overtraining (OT) model increases hypothalamus levels of some pro-inflammatory cytokines, we verified the effects of three OT protocols on the levels of BiP, pIRE-1 (Ser734), pPERK (Thr981), pelF2alpha (Ser52), ATF-6 and GRP-94 proteins in the mouse hypothalamus after two weeks of recovery. Methods: the mice were randomized into control (CT), overtrained by downhill running (OTR/down), overtrained by uphill running (OTR/up) and overtrained by running without inclination (OTR) groups. After 2-week total recovery period (i.e., week 10), hypothalamus was removed and used for immunoblotting. Results: The OTR/down group exhibited high levels of BiP and ATF6. The other OT protocols showed higher levels of pPERK (Th981) and pelf-2alpha (Ser52) when compared with the CT group. Conclusion: The current results suggest that after a 2-week total recovery period, the overtrained groups increased partially their ER stress protein levels, but without hypothalamic inflammation, which characterizes a physiological condition related to an adaptation mechanism.2
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