2,925 research outputs found
The Holographic RG flow to conformal and non-conformal theory
We review some aspects of the AdS supergravity description of RG flows. The
case of a flow to an IR CFT can be rigorously studied within the framework of
supergravity. Here we discuss various central charges of the conformal theory
(included the usually neglected ones) and we compare them with QFT
expectations. The case of flows to non-conformal theories is more problematic
in that one usually encounters a naked singularity. We mainly focus on the flow
to an IR N=1 super Yang-Mills theory. We discuss the properties of the solution
and we briefly comment on the fate of the singularity. We also compare the
supergravity results with the expectations of an N=1 SYM at strong coupling.Comment: LaTex,13 pages, 3 embedded eps figures, minor changes.Contribution to
the proceedings of the TMR Conference on Quantum Aspects of Gauge Theories,
Supersymmetry and Unification, Paris, 1-7 September 199
Confinement and Condensates Without Fine Tuning in Supergravity Duals of Gauge Theories
We discuss a solution of the equations of motion of five-dimensional gauged
type IIB supergravity that describes confining SU(N) gauge theories at large N
and large 't Hooft parameter. We prove confinement by computing the Wilson
loop, and we show that our solution is generic, independent of most of the
details of the theory. In particular, the Einstein-frame metric near its
singularity, and the condensates of scalar, composite operators are universal.
Also universal is the discreteness of the glueball mass spectrum and the
existence of a mass gap. The metric is also identical to a generically
confining solution recently found in type 0B theory.Comment: 19 pages, Late
Novel Local CFT and Exact Results on Perturbations of N=4 Super Yang Mills from AdS Dynamics
We find new, local, non-supersymmetric conformal field theories obtained by
relevant deformations of the N=4 super Yang Mills theory in the large
limit. We contruct interpolating supergravity solutions that naturally
represent the flow from the N=4 super Yang Mills UV theory to these
non-supersymmetric IR fixed points. We also study the linearization around the
N=4 superconformal point of N=1 supersymmetric, marginal deformations. We show
that they give rise to N=1 superconformal fixed points, as expected from
field-theoretical arguments.Comment: Version accepted by JHE
High frequency repetitive transcranial magnetic stimulation to the left dorsolateral prefrontal cortex modulates sensorimotor cortex function in the transition to sustained muscle pain
Based on reciprocal connections between the dorsolateral prefrontal cortex (DLPFC) and basal-ganglia regions associated with sensorimotor cortical excitability, it was hypothesized that repetitive transcranial magnetic stimulation (rTMS) of the left DLPFC would modulate sensorimotor cortical excitability induced by muscle pain. Muscle pain was provoked by injections of nerve growth factor (end of Day-0 and Day-2) into the right extensor carpi radialis brevis (ECRB) muscle in two groups of 15 healthy participants receiving 5 daily sessions (Day-0 to Day-4) of active or sham rTMS. Muscle pain scores and pressure pain thresholds (PPTs) were collected (Day-0, Day-3, Day-5). Assessment of motor cortical excitability using TMS (mapping cortical ECRB muscle representation) and somatosensory evoked potentials (SEPs) from electrical stimulation of the right radial nerve were recorded at Day-0 and Day-5. At Day-0 versus Day-5, the sham compared to active group showed: Higher muscle pain scores and reduced PPTs (P < 0.04); decreased frontal N30 SEP (P < 0.01); increased TMS map volume (P < 0.03). These results indicate that muscle pain exerts modulatory effects on the sensorimotor cortical excitability and left DLPFC rTMS has analgesic effects and modulates pain-induced sensorimotor cortical adaptations. These findings suggest an important role of prefrontal to basal-ganglia function in sensorimotor cortical excitability and pain processing
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Control of across-wind vortex shedding induced vibrations in tall buildings using the tuned mass-damper-inerter (TMDI)
In this paper, the effectiveness of the tuned mass-damper-inerter (TMDI) vis-Ã -vis the classical tuned mass-damper (TMD) is assessed to suppress vortex shedding induced vibrations to tall building structures in the across-wind direction. The TMDI, previously proposed in the literature to mitigate earthquake-induced vibrations in multi-storey buildings, benefits from the mass amplification effect of the inerter (i.e., a two-terminal device developing a resisting force proportional to the relative acceleration of its terminals by the inertance constant) to achieve improved vibration suppression performance from the classical TMD for the same attached mass. Herein, a linear reduced-order structural system is developed, defined by a diagonal mass matrix and full damping and stiffness matrices, which captures faithfully the dynamic properties of a detailed finite element model corresponding to a benchmark 74-storey building with square floor plan. A TMDI is added to the structural system by elementary operations to the mass, damping, and stiffness matrices under the assumption of an ideal linear inerter. The wind action is represented by an analytical spectral density matrix modelling correlated across-wind induced forces accounting for vortex shedding and the structural analysis step is undertaken in the frequency domain for efficiency. A comprehensive parametric analysis is undertaken demonstrating that the TMDI achieves better performance in terms of peak top floor acceleration reduction with increasing inertance than a classical TMD with the same attached mass. This is also true for relatively small attached masses of practical interest to tall buildings (less than 0.5% the total buildings mass) for the case of peak top floor displacements. Further, it is shown that the TMDI reduces significantly the peak attached mass displacement, while the peak developing forces at the inerter are not excessive and can be locally accommodated by the building
Produção de semente genética de arroz irrigado através do sistema de transplante de mudas.
bitstream/item/31543/1/comunicado60.pd
A Psychophysical Investigation of Differences between Synchrony and Temporal Order Judgments.
Synchrony judgments involve deciding whether cues to an event are in synch or out of synch, while temporal order judgments involve deciding which of the cues came first. When the cues come from different sensory modalities these judgments can be used to investigate multisensory integration in the temporal domain. However, evidence indicates that that these two tasks should not be used interchangeably as it is unlikely that they measure the same perceptual mechanism. The current experiment further explores this issue across a variety of different audiovisual stimulus types
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