2,767 research outputs found
Maximum entropy approach to power-law distributions in coupled dynamic-stochastic systems
Statistical properties of coupled dynamic-stochastic systems are studied
within a combination of the maximum information principle and the
superstatistical approach. The conditions at which the Shannon entropy
functional leads to a power-law statistics are investigated. It is demonstrated
that, from a quite general point of view, the power-law dependencies may appear
as a consequence of "global" constraints restricting both the dynamic phase
space and the stochastic fluctuations. As a result, at sufficiently long
observation times the dynamic counterpart is driven into a non-equilibrium
steady state whose deviation from the usual exponential statistics is given by
the distance from the conventional equilibrium
Disorder induced critical phenomena in magnetically glassy Cu-Al-Mn alloys
Measurements of magnetic hysteresis loops in Cu-Al-Mn alloys of different Mn
content at low temperatures are presented. The loops are smooth and continuous
above a certain temperature, but exhibit a magnetization discontinuity below
that temperature. Scaling analysis suggest that this system displays a disorder
induced phase transition line. Measurements allow to determine the critical
exponents and in agreement
with those reported recently [Berger et al., Phys. Rev. Lett. {\bf 85}, 4176
(2000)]Comment: 4 pages, 5 figure
METing SUSY on the Z peak
Recently the ATLAS experiment announced a 3 excess at the Z-peak
consisting of 29 pairs of leptons together with two or more jets, GeV and GeV, to be compared with
expected lepton pairs in the Standard Model. No excess outside the Z-peak was
observed. By trying to explain this signal with SUSY we find that only
relatively light gluinos, TeV, together with a
heavy neutralino NLSP of GeV decaying
predominantly to Z-boson plus a light gravitino, such that nearly every gluino
produces at least one Z-boson in its decay chain, could reproduce the excess.
We construct an explicit general gauge mediation model able to reproduce the
observed signal overcoming all the experimental limits. Needless to say, more
sophisticated models could also reproduce the signal, however, any model would
have to exhibit the following features, light gluinos, or heavy particles with
a strong production cross-section, producing at least one Z-boson in its decay
chain. The implications of our findings for the Run II at LHC with the scaling
on the Z peak, as well as for the direct search of gluinos and other SUSY
particles, are pointed out.Comment: 24 pages, 17 figures, simulation improved, Checkmate analysis added,
new benchmark point included. Typos corrected, conclusions unchange
Hysteresis and Avalanches in the Random Anisotropy Ising Model
The behaviour of the Random Anisotropy Ising model at T=0 under local
relaxation dynamics is studied. The model includes a dominant ferromagnetic
interaction and assumes an infinite anisotropy at each site along local
anisotropy axes which are randomly aligned. Two different random distributions
of anisotropy axes have been studied. Both are characterized by a parameter
that allows control of the degree of disorder in the system. By using numerical
simulations we analyze the hysteresis loop properties and characterize the
statistical distribution of avalanches occuring during the metastable evolution
of the system driven by an external field. A disorder-induced critical point is
found in which the hysteresis loop changes from displaying a typical
ferromagnetic magnetization jump to a rather smooth loop exhibiting only tiny
avalanches. The critical point is characterized by a set of critical exponents,
which are consistent with the universal values proposed from the study of other
simpler models.Comment: 40 pages, 21 figures, Accepted for publication in Phys. Rev.
General Flavor Blind MSSM and CP Violation
We study the implications on flavor changing neutral current and CP violating
processes in the context of supersymmetric theories without a new flavor
structure (flavor blind supersymmetry). The low energy parameters are
determined by the running of the soft breaking terms from the grand unified
scale with SUSY phases consistent with the EDM constraints. We find that the CP
asymmetry in b --> s gamma can reach large values potentially measurable at B
factories, especially in the low BR(b --> s gamma) region. We perform a fit of
the unitarity triangle including all the relevant observables. In this case, no
sizeable deviations from the SM expectations are found. Finally we analyze the
SUSY contributions to the anomalous magnetic moment of the muon pointing out
its impact on the b --> s gamma CP asymmetry and on the SUSY spectrum including
chargino and stop masses.Comment: 40 pages, 8 figures, typos corrected, references adde
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