17,065 research outputs found
Characterization of the initial filamentation of a relativistic electron beam passing through a plasma
The linear instability that induces a relativistic electron beam passing
through a return plasma current to filament transversely is often related to
some filamentation mode with wave vector normal to the beam or confused with
Weibel modes. We show that these modes may not be relevant in this matter and
identify the most unstable mode on the two-stream/filamentation branch as the
main trigger for filamentation. This sets both the characteristic transverse
and longitudinal filamentation scales in the non-resistive initial stage.Comment: 4 page, 3 figures, to appear in PR
Sensitivity and pointing accuracy of the NEMO km telescope
n this paper we present the results of Monte Carlo simulation studies on the
capability of the proposed NEMO km3 telescope to detect high energy neutrinos.
We calculated the detector sensitivity to muon neutrinos coming from a generic
point-like source. We also simulated the lack of atmospheric muons in
correspondence to the Moon disk in order to determine the detector angular
resolution and to check the absolute pointing capability.Comment: To be published on VLVNT2 proceedings (Catania, Italy, November 8-11,
2005
Effects of unparticle on top spin correlation at the Large Hadron Collider
We study effects of the scale invariant hidden sector, unparticle, proposed
by Georgi, on top spin correlation at the Large Hadron Collider. Assuming no
flavor changing interaction between the unparticles and the Standard Model
particles, there arises the top-antitop quark pair production process through
virtual unparticle exchanges in the s-channel in addition to the Standard Model
processes. In particular, we consider contributions of scalar and vector
unparticles and find that these make sizable deviations of the top spin
correlation from the Standard Model one.Comment: 29 pages, 1 table, 12 figures, 2 figures added, typos in captions
corrected, version accepted for publication in PR
Statistical mechanics of lossy compression using multilayer perceptrons
Statistical mechanics is applied to lossy compression using multilayer
perceptrons for unbiased Boolean messages. We utilize a tree-like committee
machine (committee tree) and tree-like parity machine (parity tree) whose
transfer functions are monotonic. For compression using committee tree, a lower
bound of achievable distortion becomes small as the number of hidden units K
increases. However, it cannot reach the Shannon bound even where K -> infty.
For a compression using a parity tree with K >= 2 hidden units, the rate
distortion function, which is known as the theoretical limit for compression,
is derived where the code length becomes infinity.Comment: 12 pages, 5 figure
Sensitivity of the NEMO telescope to neutrinos from microquasars
We present the results of Monte Carlo simulation studies of the capability of
the proposed NEMO telescope to detect TeV muon neutrinos from Galactic
microquasars. In particular we determined the number of the detectable events
from each known microquasar together with the expected atmospheric neutrino and
muon background events. We also discuss the detector sensitivity to neutrino
fluxes expected from microquasars, optimizing the event selection in order to
reject the atmospheric background, and we show the number of events surviving
the event selection.Comment: To be published on CRIS06 proceedings (Catania, Italy, May 29 - June
2, 2006
Generating functional analysis of CDMA detection dynamics
We investigate the detection dynamics of the parallel interference canceller
(PIC) for code-division multiple-access (CDMA) multiuser detection, applied to
a randomly spread, fully syncronous base-band uncoded CDMA channel model with
additive white Gaussian noise (AWGN) under perfect power control in the
large-system limit. It is known that the predictions of the density evolution
(DE) can fairly explain the detection dynamics only in the case where the
detection dynamics converge. At transients, though, the predictions of DE
systematically deviate from computer simulation results. Furthermore, when the
detection dynamics fail to convergence, the deviation of the predictions of DE
from the results of numerical experiments becomes large. As an alternative,
generating functional analysis (GFA) can take into account the effect of the
Onsager reaction term exactly and does not need the Gaussian assumption of the
local field. We present GFA to evaluate the detection dynamics of PIC for CDMA
multiuser detection. The predictions of GFA exhibits good consistency with the
computer simulation result for any condition, even if the dynamics fail to
convergence.Comment: 14 pages, 3 figure
Higgs Masses in the Minimal SUSY SO(10) GUT
We explicitly show that minimal SUSY SO(10) Higgs-Higgsino mass matrices
evaluated by various groups are mutually consistent and correct. We comment on
the corresponding results of other authors. We construct one-to-one mappings of
our approach to the approaches of other authors.Comment: 4 pages, revtex4, Changes in the paper : We agree with Ref.
hep-ph/0501025 that there there should exist equivalence mappings between
results of Higgs mass spectra calculated by three groups of authors. (in
three different approaches. However, in the Note added of the Ref.
hep-ph/0405074 v3 the wrong mapping was presented. The explicit construction
of equivalence mappings to other approches is given. Minor changes in the
text. Paper is beeing accepted for publication in Phys. Rev
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