341 research outputs found
A 5-Dimensional Spherical Symmetric Solution in Einstein-Yang-Mills Theory With Gauss-Bonnet Term
We present a numerical solution on a 5-dimensional spherically symmetric
space time, in Einstein-Yang-Mills-Gauss-Bonnet theory using a two point
boundary value routine. It turns out that the Gauss-Bonnet contribution has a
profound influence on the behaviour of the particle-like solution: it increases
the number of nodes of the YM field. When a negative cosmological constant in
incorporated in the model, it turns out that there is no horizon and no
singular behaviour of the model. For positive cosmological constant the model
has singular behaviour.Comment: 7 pages, 6 figure
Tracking Real-Time Changes in Working Memory Updating and Gating with the Event-Based Eye-Blink Rate
Melvin solution with a dilaton potential
We find new Melvin-like solutions in Einstein-Maxwell-dilaton gravity with a
Liouville-type dilaton potential. The properties of the corresponding solution
in Freedman-Schwarz gauged supergravity model are extensively studied. We show
that this configuration is regular and geodesically complete but do not
preserve any supersymmetry. An exact solution describing travelling waves in
this Melvin-type background is also presented.Comment: 12 pages, LaTeX, no figure
High-Frequency Gravitational Waves from Spinning Non-Abelian Cosmic-Strings
We investigated the SU(2) Einstein-Yang-Mills system on a time-dependent
non-diagonal cylindrical symmetric space-time. From the numerical
investigation, wave-like solutions are found, consistent with the familiar
string-like features. They possess an angle-deficit which depends on the
initial form of the magnetic component of the YM field, i.e., the number of
times it crosses the r-axis. The soliton-like behavior of the gravitational and
YM waves show significant differences from the ones found in the
Einstein-Maxwell system. The stability of the system is analyzed using the
multiple-scale method. To first order a consistent set of equations is
obtained.Comment: 26 pages in Revtex+ 10 eps figures. The other pictures can be
obtained at http://www.asfyon.nl/slagt.html/webdoc.ht
Repetitive Transcranial Magnetic Stimulation Affects behavior by Biasing Endogenous Cortical Oscillations
A governing assumption about repetitive transcranial magnetic stimulation (rTMS) has been that it interferes with task-related neuronal activity – in effect, by “injecting noise” into the brain – and thereby disrupts behavior. Recent reports of rTMS-produced behavioral enhancement, however, call this assumption into question. We investigated the neurophysiological effects of rTMS delivered during the delay period of a visual working memory task by simultaneously recording brain activity with electroencephalography (EEG). Subjects performed visual working memory for locations or for shapes, and in half the trials a 10-Hz train of rTMS was delivered to the superior parietal lobule (SPL) or a control brain area. The wide range of individual differences in the effects of rTMS on task accuracy, from improvement to impairment, was predicted by individual differences in the effect of rTMS on power in the alpha-band of the EEG (∼10 Hz): a decrease in alpha-band power corresponded to improved performance, whereas an increase in alpha-band power corresponded to the opposite. The EEG effect was localized to cortical sources encompassing the frontal eye fields and the intraparietal sulcus, and was specific to task (location, but not object memory) and to rTMS target (SPL, not control area). Furthermore, for the same task condition, rTMS-induced changes in cross-frequency phase synchrony between alpha- and gamma-band (>40 Hz) oscillations predicted changes in behavior. These results suggest that alpha-band oscillations play an active role cognitive processes and do not simply reflect absence of processing. Furthermore, this study shows that the complex effects of rTMS on behavior can result from biasing endogenous patterns of network-level oscillations
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