1,653 research outputs found
A new approach of analyzing GRB light curves
We estimated the Txx quantiles of the cumulative GRB light curves using our
recalculated background. The basic information of the light curves was
extracted by multivariate statistical methods. The possible classes of the
light curves are also briefly discussed.Comment: 4 pages, 8 figure
Semantic Compression of Episodic Memories
Storing knowledge of an agent's environment in the form of a probabilistic
generative model has been established as a crucial ingredient in a multitude of
cognitive tasks. Perception has been formalised as probabilistic inference over
the state of latent variables, whereas in decision making the model of the
environment is used to predict likely consequences of actions. Such generative
models have earlier been proposed to underlie semantic memory but it remained
unclear if this model also underlies the efficient storage of experiences in
episodic memory. We formalise the compression of episodes in the normative
framework of information theory and argue that semantic memory provides the
distortion function for compression of experiences. Recent advances and
insights from machine learning allow us to approximate semantic compression in
naturalistic domains and contrast the resulting deviations in compressed
episodes with memory errors observed in the experimental literature on human
memory.Comment: CogSci201
Diffusion Processes on Power-Law Small-World Networks
We consider diffusion processes on power-law small-world networks in
different dimensions. In one dimension, we find a rich phase diagram, with
different transient and recurrent phases, including a critical line with
continuously varying exponents. The results were obtained using self-consistent
perturbation theory and can also be understood in terms of a scaling theory,
which provides a general framework for understanding processes on small-world
networks with different distributions of long-range links.Comment: 4 pages, 3 figures, added references, modified Fig. 2 with added data
(PRL, in press
Investigation the connection between the intermediate gamma-ray bursts and X-ray flashes
Gamma-ray bursts can be divided into three groups: short-, intermediate and
long-duration bursts. While the progenitors of the short and long ones are
relatively known, the progenitor objects of the intermediate-duration bursts
are generally unknown, however, recent statistical studies suggest, that they
should be related to the long-duration bursts. In this work we investigate
whether there is a differ- ence between the global parameters of the X-ray
flashes and intermediate-duration group of gamma-ray bursts. The statistical
tests do not show any significant discrepancy regarding most of the parameters,
except the BAT photon index, which is only a consequence of the defintion of
the X-ray flashes.Comment: 9 pages, 10 figures, submitted to Astronomische Nachrichte
The pseudogap phase in (TaSe_4)_2I
We have developed the mean-field theory of coexisting charge-density waves
(CDW) and unconventional charge-density waves (UCDW). The double phase
transition manifests itself in the thermodynamic quantities and in the magnetic
response, such as spin susceptibility and spin-lattice relaxation rate. Our
theory applies to quasi-one dimensional (TaSe_4)_2I, where above the CDW
transition, thermal fluctuations die out rapidly, but robust pseudogap
behaviour is still detected. We argue, that the fluctuations are suppressed due
to UCDW, which partially gaps the Fermi surface, and causes non-Fermi-liquid
(pseudogap) behaviour.Comment: 7 pages, 6 figure
Mean-field quantum phase transition in graphene and in general gapless systems
We study the quantum critical properties of antiferromagnetism in graphene at
T=0 within mean-field (MF) theory. The resulting exponents differ from the
conventional MF exponents, describing finite temperature transitions. Motivated
by this, we have developed the MF theory of general gapless phases with density
of states rho(E) |E|^r, r>-1, with the interaction as control parameter. For
r>2, the conventional MF exponents \'a la Landau are recovered, while for
-1<r<2, the exponents vary significantly with r. The critical interaction is
finite for r>0, therefore no weak-coupling solution exists in this range. This
generalizes the results on quantum criticality of the gapless Kondo systems to
bulk correlated phases.Comment: 5 pages, 1 figure, 2 table
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