2,690 research outputs found
An anisotropic hybrid non-perturbative formulation for 4D N = 2 supersymmetric Yang-Mills theories
We provide a simple non-perturbative formulation for non-commutative
four-dimensional N = 2 supersymmetric Yang-Mills theories. The formulation is
constructed by a combination of deconstruction (orbifold projection), momentum
cut-off and matrix model techniques. We also propose a moduli fixing term that
preserves lattice supersymmetry on the deconstruction formulation. Although the
analogous formulation for four-dimensional N = 2 supersymmetric Yang-Mills
theories is proposed also in Nucl.Phys.B857(2012), our action is simpler and
better suited for computer simulations. Moreover, not only for the
non-commutative theories, our formulation has a potential to be a
non-perturbative tool also for the commutative four-dimensional N = 2
supersymmetric Yang-Mills theories.Comment: 32 pages, final version accepted in JHE
Lattice formulation of two-dimensional N=(2,2) super Yang-Mills with SU(N) gauge group
We propose a lattice model for two-dimensional SU(N) N=(2,2) super Yang-Mills
model. We start from the CKKU model for this system, which is valid only for
U(N) gauge group. We give a reduction of U(1) part keeping a part of
supersymmetry. In order to suppress artifact vacua, we use an admissibility
condition.Comment: 16 pages, 3 figures; v2: typo crrected; v3: 18 pages, a version to
appear in JHE
Non-lattice simulation for supersymmetric gauge theories in one dimension
Lattice simulation of supersymmetric gauge theories is not straightforward.
In some cases the lack of manifest supersymmetry just necessitates cumbersome
fine-tuning, but in the worse cases the chiral and/or Majorana nature of
fermions makes it difficult to even formulate an appropriate lattice theory. We
propose to circumvent all these problems inherent in the lattice approach by
adopting a non-lattice approach in the case of one-dimensional supersymmetric
gauge theories, which are important in the string/M theory context.Comment: REVTeX4, 4 pages, 3 figure
Absence of sign problem in two-dimensional N=(2,2) super Yang-Mills on lattice
We show that N=(2,2) SU(N) super Yang-Mills theory on lattice does not have
sign problem in the continuum limit, that is, under the phase-quenched
simulation phase of the determinant localizes to 1 and hence the phase-quench
approximation becomes exact. Among several formulations, we study models by
Cohen-Kaplan-Katz-Unsal (CKKU) and by Sugino. We confirm that the sign problem
is absent in both models and that they converge to the identical continuum
limit without fine tuning. We provide a simple explanation why previous works
by other authors, which claim an existence of the sign problem, do not capture
the continuum physics.Comment: 27 pages, 24 figures; v2: comments and references added; v3: figures
on U(1) mass independence and references added, to appear in JHE
Phase structure of twisted Eguchi-Kawai model
We study the phase structure of the four-dimensional twisted Eguchi-Kawai
model using numerical simulations. This model is an effective tool for studying
SU(N) gauge theory in the large-N limit and provides a nonperturbative
formulation of the gauge theory on noncommutative spaces. Recently it was found
that its Z_N^4 symmetry, which is crucial for the validity of this model, can
break spontaneously in the intermediate coupling region. We investigate in
detail the symmetry breaking point from the weak coupling side. Our simulation
results show that the continuum limit of this model cannot be taken.Comment: 7 pages, 4 figures, talk presented at the XXV International Symposium
on Lattice Field Theory, July 30 - August 4, 2007, Regensburg, German
Cross-modal cue effects in motion processing
The everyday environment brings to our sensory systems competing inputs from different modalities. The ability to filter these multisensory inputs in order to identify and efficiently utilize useful spatial cues is necessary to detect and process the relevant information. In the present study, we investigate how feature-based attention affects the detection of motion across sensory modalities. We were interested to determine how subjects use intramodal, cross-modal auditory, and combined audiovisual motion cues to attend to specific visual motion signals. The results showed that in most cases, both the visual and the auditory cues enhance feature-based orienting to a transparent visual motion pattern presented among distractor motion patterns. Whereas previous studies have shown cross-modal effects of spatial attention, our results demonstrate a spread of cross-modal feature-based attention cues, which have been matched for the detection threshold of the visual target. These effects were very robust in comparisons of the effects of valid vs. invalid cues, as well as in comparisons between cued and uncued valid trials. The effect of intramodal visual, cross-modal auditory, and bimodal cues also increased as a function of motion-cue salience. Our results suggest that orienting to visual motion patterns among distracters can be facilitated not only by intramodal priors, but also by feature-based cross-modal information from the auditory system.First author draf
Quantum chaos, thermalization, and entanglement generation in real-time simulations of the Banks-Fischler-Shenker-Susskind matrix model
We study numerically the onset of chaos and thermalization in the Banks-Fischler-Shenker-Susskind (BFSS) matrix model with and without fermions, considering Lyapunov exponents, entanglement generation, and quasinormal ringing. We approximate the real-time dynamics in terms of the most general Gaussian density matrices with parameters which obey self-consistent equations of motion, thus extending the applicability of real-time simulations beyond the classical limit. Initial values of these Gaussian density matrices are optimized to be as close as possible to the thermal equilibrium state of the system. Thus attempting to bridge between the low-energy regime with a calculable holographic description and the classical regime at high energies, we find that quantum corrections to classical dynamics tend to decrease the Lyapunov exponents, which is essential for consistency with the Maldacena-Shenker-Stanford bound at low temperatures. The entanglement entropy is found to exhibit an expected "scrambling" behavior-rapid initial growth followed by saturation. At least at high temperatures the entanglement saturation time appears to be governed by classical Lyapunov exponents. Decay of quasinormal modes is found to be characterized by the shortest timescale of all. We also find that while the bosonic matrix model becomes nonchaotic in the low-temperature regime, for the full BFSS model with fermions the leading Lyapunov exponent, entanglement saturation time, and decay rate of quasinormal modes all remain finite and nonzero down to the lowest temperatures
Numerical studies of the ABJM theory for arbitrary N at arbitrary coupling constant
We show that the ABJM theory, which is an N=6 superconformal U(N)*U(N)
Chern-Simons gauge theory, can be studied for arbitrary N at arbitrary coupling
constant by applying a simple Monte Carlo method to the matrix model that can
be derived from the theory by using the localization technique. This opens up
the possibility of probing the quantum aspects of M-theory and testing the
AdS_4/CFT_3 duality at the quantum level. Here we calculate the free energy,
and confirm the N^{3/2} scaling in the M-theory limit predicted from the
gravity side. We also find that our results nicely interpolate the analytical
formulae proposed previously in the M-theory and type IIA regimes. Furthermore,
we show that some results obtained by the Fermi gas approach can be clearly
understood from the constant map contribution obtained by the genus expansion.
The method can be easily generalized to the calculations of BPS operators and
to other theories that reduce to matrix models.Comment: 35 pages, 20 figures; reference added. The simulation code is
available upon request to [email protected]
Monte Carlo studies of supersymmetric matrix quantum mechanics with sixteen supercharges at finite temperature
We present the first Monte Carlo results for supersymmetric matrix quantum
mechanics with sixteen supercharges at finite temperature. The recently
proposed non-lattice simulation enables us to include the effects of fermionic
matrices in a transparent and reliable manner. The internal energy nicely
interpolates the weak coupling behavior obtained by the high temperature
expansion, and the strong coupling behavior predicted from the dual black hole
geometry. The Polyakov line takes large values even at low temperature
suggesting the absence of a phase transition in sharp contrast to the bosonic
case. These results provide highly non-trivial evidences for the gauge/gravity
duality.Comment: REVTeX4, 4 pages, 3 figure
Incidência e identificação de fungos em sementes de híbrido interespecífico BRS-Manicoré: dendê (Elaeis guineensis Jacq.) x caiaué (Elaeis oleífera (Kunth) Cortés).
O dendezeiro ou palma de óleo (Elaeis guineensis) é uma palmeira originária da África com alta produtividade. A hibridação interespecífica entre o caiaué (Elaeis oleífera) e o dendezeiro desenvolve cultivares produtivos, resistentes a pragas e doenças. Este trabalho teve por objetivo avaliar a incidência e identificar fungos presentes em sementes de BRS-Manicoré
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