5,770 research outputs found
Search for a heavy magnetic monopole at the Fermilab Tevatron and CERN LHC
If a heavy Dirac monopole exists, the light to light scattering below the
monopole production threshold is enhanced due to the strong coupling of
monopoles to photons. This effect could be observable in the collision of
virtual photons at proton colliders. At the Tevatron it will be seen as pair
production of photons with energies 200--400 GeV and roughly compensated
transverse momenta 100--400 GeV/c. This effect could be seen at monopole masses
about 1--2.5 TeV at the upgraded Tevatron and 7.4--19 TeV at LHC depending on
monopole spin.Comment: 11 pages, 2 figures, Latex(Revtex), small changes in estimates of
Sect.III and in Fig.2 due to corrected form factor scale of eq. (19), title
made more precis
Charge asymmetry of pions in the process
The study of the charge asymmetry of produced particles allows to investigate
the interference of different production mechanisms and to determine new
features of the corresponding amplitudes. In the process the two-pion system is produced via two mechanisms: two-photon
(C-even state) and bremsstrahlung (C-odd state) production. We study the charge
asymmetry of pions in a differential in the pion momenta cross section
originating from an interference between these two mechanisms. At low effective
mass of dipions this asymmetry is directly related to the s- and p-phases of
elastic scattering. At higher energies it can give new information
about the meson family, meson, etc. The asymmetry is
expressed via the pion form factor and helicity amplitudes for
the subprocess as where we have calculated analytically the coefficients
for the region giving the main contribution to the effect. Several
distributions of pions are presented performing a numerical analysis in a model
with point-like pions. In the region near the dipion threshold the asymmetry is
of the order of 1%. We show that with suitable cuts the signal to background
ratio can be increased up to about 10%.Comment: 16 pages, 10 figures, LaTeX, style files for EPJC include
Optimal Investment Horizons for Stocks and Markets
The inverse statistics is the distribution of waiting times needed to achieve
a predefined level of return obtained from (detrended) historic asset prices
\cite{optihori,gainloss}. Such a distribution typically goes through a maximum
at a time coined the {\em optimal investment horizon}, , which
defines the most likely waiting time for obtaining a given return . By
considering equal positive and negative levels of return, we reported in
\cite{gainloss} on a quantitative gain/loss asymmetry most pronounced for short
horizons. In the present paper, the inverse statistics for 2/3 of the
individual stocks presently in the DJIA is investigated. We show that this
gain/loss asymmetry established for the DJIA surprisingly is {\em not} present
in the time series of the individual stocks nor their average. This observation
points towards some kind of collective movement of the stocks of the index
(synchronization).Comment: Subm. to Physica A as Conference Proceedings of Econophysics
Colloquium, ANU Canberra, 13-17 Nov. 2005. 6 pages including figure
Quantum quenches and driven dynamics in a single-molecule device
The nonequilibrium dynamics of molecular devices is studied in the framework
of a generic model for single-molecule transistors: a resonant level coupled by
displacement to a single vibrational mode. In the limit of a broad level and in
the vicinity of the resonance, the model can be controllably reduced to a form
quadratic in bosonic operators, which in turn is exactly solvable. The response
of the system to a broad class of sudden quenches and ac drives is thus
computed in a nonperturbative manner, providing an asymptotically exact
solution in the limit of weak electron-phonon coupling. From the analytic
solution we are able to (1) explicitly show that the system thermalizes
following a local quantum quench, (2) analyze in detail the time scales
involved, (3) show that the relaxation time in response to a quantum quench
depends on the observable in question, and (4) reveal how the amplitude of
long-time oscillations evolves as the frequency of an ac drive is tuned across
the resonance frequency. Explicit analytical expressions are given for all
physical quantities and all nonequilibrium scenarios under study.Comment: 23 pages, 13 figure
Visions of Global Electronic Mastery
Este texto es una de las últimas aportaciones del pionero de la Economía Política de la Comunicación Herbert I. Schiller. El él mantiene una de sus líneas de investigación fundamentales: la extensión de la doctrina del libre flujo de la información como parte de la política exterior estadounidense. Sólo que en este caso se aplica al comercio electrónico y la era digital. En este sentido uno de lo documentos analizados en profundidad por el autor, The Framework for Global Electronic Comerce, representa la actualización de la doctrina. De esta manera el mantenimiento de la hegemonía de Estados Unidos y su supremacía electrónica global serán posibles a lo largo del siglo XXI.This text is one of the last contributions of pioneer of Political Economy of Communication Herbert I. Schiller. The author keeps up with one of his fundamental thesis, that is, the extension of the free flow of information doctrine as part of the US foreign policy. In this case it is applied to electronic commerce and the digital era. In this sense one of the documents analysed in depth by the author, The Framework for Electronic Commerce, represents the actualization of this doctrine. Thus the preservation of US hegemony and its global electronic mastery will be a fact along the 21st century
Lattice study of the infrared behavior of QCD Green's functions in Landau gauge
We summarize the current status of our numerical results for the gluon and
ghost propagators and for the Kugo-Ojima confinement parameter in quenched
SU(3) lattice Landau gauge theory. The data for the propagators are compared to
our results obtained in the case of full QCD, simulated using two flavors of
dynamical clover-improved Wilson fermions. We demonstrate that the infrared
behavior of the ghost propagator is consistent with the Kugo-Ojima confinement
criterion. Explicit violation of reflection positivity by the gluon propagator
is shown. Additionally, we present results of a running coupling constant both
at low and at large momenta.Comment: 7 pages, 8 figures, talk presented at Lattice2006 (Confinement and
Topology
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