1,707 research outputs found
Quasi-Normal Modes of Extremal BTZ Black Holes in TMG
We study the spectrum of tensor perturbations on extremal BTZ black holes in
topologically massive gravity for arbitrary values of the coefficient of the
Chern-Simons term, . Imposing proper boundary conditions at the boundary
of the space and at the horizon, we find that the spectrum contains
quasi-normal modes.Comment: 18 pages, Latex, Ref's added, Typos correcte
Extended massive gravity in three dimensions
Using a first order Chern-Simons-like formulation of gravity we
systematically construct higher-derivative extensions of general relativity in
three dimensions. The construction ensures that the resulting higher-derivative
gravity theories are free of scalar ghosts. We canonically analyze these
theories and construct the gauge generators and the boundary central charges.
The models we construct are all consistent with a holographic c-theorem which,
however, does not imply that they are unitary. We find that Born-Infeld gravity
in three dimensions is contained within these models as a subclass.Comment: 35p, v2; minor changes, references adde
Relationship of some risk factors and symptoms in patients with acute coronary syndrome
Acute coronary syndrome (ACS) is one of the major causes of death in the worldwide. Clinical manifestations are different. So it's necessary to have knowledge about the types of symptoms experienced by patients with ACS. This study was performed to assay the Relationship of some risk factors and symptoms in patients with acute coronary syndrome. This cross-sectional study, were studied 294 patients with acute coronary syndrome at least 24 hours after admission had survived. Data was collected by a questionnaire that included demographic data form and check list of some symptoms and history of risk factors. There was a significant relationship between STEMI with vomiting (OR=1.94) and anxiety (OR=1.83) and UA with vomiting (OR=0.42). Between sex with weakness (OR=2.29) and anxiety (OR=1.82), diabetes with dyspenea (OR=1.8), weakness (OR=1.02) and tinnitus (OR=2.06) and hyperlipidemia with weakness (OR=2.35) and tinnitus (OR=2.49) was available significant difference. The findings of this study indicate that the appearance of symptoms of acute coronary syndrome were different as for ECG changes and risk factors, and more focused on those symptoms that they are common with any other diseases. Since, many of the symptoms of acute coronary syndrome can be potentially dangerous and life threatening, accurate diagnosis and timely action is crucial for the patients
Covariant Poisson's equation in torsional Newton-Cartan gravity
We derive the covariant Poisson's equation of (d+1)-dimensional Newton-Cartan
gravity with (twistless) torsion by applying the `non-relativistic conformal
method' introduced in arXiv:1512.06277. We apply this method on-shell to a
Schr\"odinger field theory on the curved Newton-Hooke background. The
covariance of the field equation in the presence of the non-relativistic
cosmological constant, entails fixing all coefficients in the covariant
Poisson's equation for (twistless) torsional Newton-Cartan gravity. We further
derive Ehlers conditions and an equation associated to the torsion in this
method.Comment: 20 pages, v2 references adde
Synthesis of neural networks for spatio-temporal spike pattern recognition and processing
The advent of large scale neural computational platforms has highlighted the
lack of algorithms for synthesis of neural structures to perform predefined
cognitive tasks. The Neural Engineering Framework offers one such synthesis,
but it is most effective for a spike rate representation of neural information,
and it requires a large number of neurons to implement simple functions. We
describe a neural network synthesis method that generates synaptic connectivity
for neurons which process time-encoded neural signals, and which makes very
sparse use of neurons. The method allows the user to specify, arbitrarily,
neuronal characteristics such as axonal and dendritic delays, and synaptic
transfer functions, and then solves for the optimal input-output relationship
using computed dendritic weights. The method may be used for batch or online
learning and has an extremely fast optimization process. We demonstrate its use
in generating a network to recognize speech which is sparsely encoded as spike
times.Comment: In submission to Frontiers in Neuromorphic Engineerin
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