460 research outputs found
Signal estimation and threshold optimization using an array of bithreshold elements
We consider the problem of optimizing signal transmission through
multi-channel noisy devices. We investigate an array of bithreshold noisy
devices which are connected in parallel and convergent on a summing center.
Utilizing the concept of noise-induced linearization we derive an analytical
approximation of the normalized power norm and clarify the relation between the
optimum threshold and the standard deviation of noises. We show that the
optimum threshold value is 0.63 times the standard deviation of the noises.
This relation is applicable to both subthreshold and suprathreshold inputs.Comment: 14 pages, 6 figure
Quantum description for a chiral condensate disoriented in a certain direction in isospace
We derive a quantum state of the disoriented chiral condensate dynamically,
considering small quantum fluctuations around a classical chiral condensate
disoriented in a certain direction in isospace. The obtained
nonisosinglet quantum state has the characteristic features; (i) it has the
form of the squeezed state, (ii) the state contains not only the component of
pion quanta in the direction but also the component in the
perpendicular direction to and (iii) the low momentum pions in the
state violate the isospin symmetry. With the quantum state, we calculate the
probability of the neutral fraction depending on the time and the pion's
momentum, and find that the probability has an unfamiliar form. For the low
momentum pions, the parametric resonance mechanism works with the result that
the probability of the neutral fraction becomes the well known form
approximately and that the charge fluctuation is small.Comment: 19 page
Use of Hirsch Index for Measuring the Impact of IS Academic Research and Journals
This study examines the use of journal rankings and a relatively new method of measuring impact of research as a surrogate of scholarly impact: the Hirsch Index (Hirsch 2005). Journal rankings are a very important exercise in academia since they impact tenure and promotion decisions. Current methods employed to rank journal influence are shown to be subjective. We propose that the Hirsch Index be adopted as a more objective journal ranking method. To demonstrate the results of using the Hirsch Index, it is applied to the “pure MIS” journals ranked by Rainer and Miller (2005). The authors find substantial differences between the scholar rankings and those obtained using the Hirsch index. This provides weak support for the current journal ranking system but also suggests that other factors are at play
Parametric resonance at the critical temperature in high energy heavy ion collisions
Parametric resonance in soft modes at the critical temperature () in
high energy heavy ion collisions is studied in the case when the temperature
() of the system is almost constant for a long time. By deviding the fields
into three parts, zero mode (condensate), soft modes and hard modes and
assuming that the hard modes are in thermal equilibrium, we derive the equation
of motion for soft modes at . Enhanced modes are extracted by
comparing with the Mathieu equation for the condensate oscillating along the
sigma axis at . It is found that the soft mode of fields at
about 174 MeV is enhanced.Comment: 8 pages, 1 figure Some statements and equations are modified to
clarif
Parametric amplification with a friction in heavy ion collisions
We study the effects of the expansion of the system and the friction on the
parametric amplification of mesonic fields in high energy heavy ion collisions
within the linear model . The equation of motion which is similar to
Mathieu equation is derived to describe the time development of classical
fields in the last stage of a heavy ion collision after the freezeout time. The
enhanced mode is extracted analytically by comparison with Mathieu equation and
the equation of motion is solved numerically to examine whether soft modes will
be enhanced or not. It is found that the strong peak appears around 267 MeV in
the pion transverse momentum distribution in cases with weak friction and high
maximum temperature. This enhancement can be extracted by taking the ratio
between different modes in the pion transverse momentum distribution.Comment: 10 pages, 9 figures LaTeX: appendix adde
Description of a domain by a squeezed state in a scalar field theory
The author attempted to describe a domain by using a squeezed state in
quantum field theory. An extended squeeze operator was used to construct the
state. In a scalar field theory, the author described a domain that the
distributions of the condensate and of the fluctuation are Gaussian. The
momentum distribution, chaoticity and correlation length were calculated. It
was found that the typical value of the momentum is about the inverse of the
domain size, and that the chaoticity reflects the ratio of the size of the
squeeze region to that of the coherent region. The results indicate that the
quantum state of a domain is surmised by these quantities under the assumption
that the distributions are Gaussian. As an example, this method was applied to
a pion field, and the momentum distribution and the chaoticity were shown.Comment: 10 pages, 5 figures, a typographical error in the reference is
correcte
Vertex operator approach for form factors of Belavin's -symmetric model
Belavin's -symmetric model is considered on the
basis of bosonization of vertex operators in the model and
vertex-face transformation. Free field representations of nonlocal tail
operators are constructed for off diagonal matrix elements with respect to the
ground state sectors. As a result, integral formulae for form factors of any
local operators in the -symmetric model can be
obtained, in principle.Comment: 24 pages, 4 figures, published in J. Phys. A: Math. Theor. 43 (2010)
085202. For the next thirty days from Feb 5 2010, the full text of the
article will be completely free to access through our 'This Month's Papers'
service (www.iop.org/journals/thismonth), helping you to benefit from maximum
visibilit
Vertex operator approach for correlation functions of Belavin's (Z/nZ)-symmetric model
Belavin's -symmetric model is considered on the
basis of bosonization of vertex operators in the model and
vertex-face transformation. The corner transfer matrix (CTM) Hamiltonian of
-symmetric model and tail operators are expressed in
terms of bosonized vertex operators in the model. Correlation
functions of -symmetric model can be obtained by
using these objects, in principle. In particular, we calculate spontaneous
polarization, which reproduces the result by myselves in 1993.Comment: For the next thirty days the full text of this article is available
at http://stacks.iop.org/1751-8121/42/16521
Compound basis arising from the basic -module
A new basis for the polynomial ring of infinitely many variables is
constructed which consists of products of Schur functions and Q-functions. The
transition matrix from the natural Schur function basis is investigated.Comment: 12 page
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