262 research outputs found
On Multivariate Records from Random Vectors with Independent Components
Let be independent copies of a
random vector with values in and with a
continuous distribution function. The random vector is a
complete record, if each of its components is a record. As we require
to have independent components, crucial results for univariate
records clearly carry over. But there are substantial differences as well:
While there are infinitely many records in case , there occur only
finitely many in the series if . Consequently, there is a terminal
complete record with probability one. We compute the distribution of the random
total number of complete records and investigate the distribution of the
terminal record. For complete records, the sequence of waiting times forms a
Markov chain, but differently from the univariate case, now the state infinity
is an absorbing element of the state space
Some Results on Joint Record Events
Let be independent and identically distributed random
variables on the real line with a joint continuous distribution function .
The stochastic behavior of the sequence of subsequent records is well known.
Alternatively to that, we investigate the stochastic behavior of arbitrary
, under the condition that they are records, without knowing their
orders in the sequence of records. The results are completely different. In
particular it turns out that the distribution of , being a record, is not
affected by the additional knowledge that is a record as well. On the
contrary, the distribution of , being a record, is affected by the
additional knowledge that is a record as well. If has a density, then
the gain of this additional information, measured by the corresponding
Kullback-Leibler distance, is , independent of . We derive the limiting
joint distribution of two records, which is not a bivariate extreme value
distribution. We extend this result to the case of three records. In a special
case we also derive the limiting joint distribution of increments among
records
Dynamics of inflationary cosmology in TVSD model
Within the framework of a model Universe with time variable space dimensions
(TVSD), known as decrumpling or TVSD model, we study TVSD chaotic inflation and
obtain dynamics of the inflaton, scale factor and spatial dimension. We also
study the quantum fluctuations of the inflaton field and obtain the spectral
index and its running in this model. Two classes of examples have been studied
and comparisons made with the standard slow-roll formulae. We compare our
results with the recent Wilkinson Microwave Anisotropy Probe (WMAP) data.Comment: 18 pages, 3 figures, accepted in Mod. Phys. Lett.
Quantum E(2) groups and Lie bialgebra structures
Lie bialgebra structures on are classified. For two Lie bialgebra
structures which are not coboundaries (i.e. which are not determined by a
classical -matrix) we solve the cocycle condition, find the Lie-Poisson
brackets and obtain quantum group relations. There is one to one correspondence
between Lie bialgebra structures on and possible quantum deformations of
and .Comment: 8 pages, plain TEX, harvmac, to appear in J. Phys.
Phase transition in an asymmetric generalization of the zero-temperature q-state Potts model
An asymmetric generalization of the zero-temperature q-state Potts model on a
one dimensional lattice, with and without boundaries, has been studied. The
dynamics of the particle number, and specially the large time behavior of the
system has been analyzed. In the thermodynamic limit, the system exhibits two
kinds of phase transitions, a static and a dynamic phase transition.Comment: 11 pages, LaTeX2
Towards Full Aircraft Airframe Noise Prediction: Detached Eddy Simulations
Results from a computational study on the aeroacoustic characteristics of an 18%-scale, semi-span Gulf-stream aircraft model are presented in this paper. NASA's FUN3D unstructured compressible Navier-Stokes solver was used to perform steady and unsteady simulations of the flow field associated with this high-fidelity aircraft model. Solutions were obtained for free-air at a Mach number of 0.2 with the flap deflected at 39 deg, with the main gear off and on (the two baseline configurations). Initially, the study focused on accurately predicting the prominent noise sources at both flap tips for the baseline configuration with deployed flap only. Building upon the experience gained from this initial effort, subsequent work involved the full landing configuration with both flap and main landing gear deployed. For the unsteady computations, we capitalized on the Detached Eddy Simulation capability of FUN3D to capture the complex time-dependent flow features associated with the flap and main gear. To resolve the noise sources over a broad frequency range, the tailored grid was very dense near the flap inboard and outboard tips and the region surrounding the gear. Extensive comparison of the computed steady and unsteady surface pressures with wind tunnel measurements showed good agreement for the global aerodynamic characteristics and the local flow field at the flap inboard tip. However, the computed pressure coefficients indicated that a zone of separated flow that forms in the vicinity of the outboard tip is larger in extent along the flap span and chord than measurements suggest. Computed farfield acoustic characteristics from a FW-H integral approach that used the simulated pressures on the model solid surface were in excellent agreement with corresponding measurements
Autonomous multispecies reaction-diffusion systems with more-than-two-site interactions
Autonomous multispecies systems with more-than-two-neighbor interactions are
studied. Conditions necessary and sufficient for closedness of the evolution
equations of the -point functions are obtained. The average number of the
particles at each site for one species and three-site interactions, and its
generalization to the more-than-three-site interactions is explicitly obtained.
Generalizations of the Glauber model in different directions, using generalized
rates, generalized number of states at each site, and generalized number of
interacting sites, are also investigated.Comment: 9 pages, LaTeX2
Noncommutative Decrumpling Inflation and Running of the Spectral Index
We present a new inflation model, known as noncommutative decrumpling
inflation, in which space has noncommutative geometry with time variability of
the number of spatial dimensions. Within the framework of noncommutative
decrumpling inflation, we compute both the spectral index and its running. Our
results show that the effects of both time variability of the number of spatial
dimensions and noncommutative geometry on the spectral index and its running.
Two classes of examples have been studied and comparisons made with the
standard slow-roll formulae. We conclude that the effects of noncommutative
geometry on the spectral index and its running are much smaller than the
effects of time variability of spatial dimensions.Comment: 15 pages, accepted for publication in Int.J.Mod.Phys.
Seroprevalence of Toxoplasma gondii Infection in Dogs in Tehran, Iran
Background: Toxoplasma gondii infects a wide range of animals; felines are definitive hosts and other animals including the dogs are intermediate hosts. The aim of this study was to determine the seroprevalence of T. gondii infection in dogs in Tehran, capital of Iran and to investigate possiÂble associated risk factors.Methods: Three hundreds ninety six serum samples were collected during 2007-8 from the dogs. ColÂlected samples were tested using an indirect fluorescent antibody test (IFAT) in dilutions of 1:16 and more. All procedures were carried out in Shahrekord University, Iran. All the data were analyzed using SPSS software, qui square test with confidence interval of 0.95.Results: From evaluated samples, 89 (22.47%) were positive in titers of at least 1:16. further evaluaÂtions in other dilutions showed positive results in dilutions of maximum 1:16 , 1:32, 1:64, 1:128 and 1:256 in 38, 29, 15, 2 and 5 dogs respectively. Investigation of the role of risk factors showed no sex predisposition while infection rate was significantly higher in dogs older than one year old. Living places were of significant importance; infection rate was significantly higher in stray or guard dogs in compare with household dogs (P<0.05). Conclusion: Relatively high seroprevalence of T. gondii infection in dogs in Tehran shows high environmental contamination. It is recommended that the dogs with suspected clinical signs be tested for T. gondii infection
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