499 research outputs found
Indirect Signals from Dark Matter in Split Supersymmetry
We study the possibilities for the indirect detection of dark matter in Split
Supersymmetry from gamma-rays, positrons, and antiprotons. The most promising
signal is the gamma-ray line, which may be observable at the next generation of
detectors. For certain halo profiles and a high mass neutralino, the line can
even be visible in current experiments. The continuous gamma-ray signal may be
observable, if there is a central spike in the galactic halo density. The
signals are found to be similar to those in MSSM models. These indirect signals
complement other experiments, being most easily observable for regions of
parameter space, such as heavy wino and higgsino dominated neutralinos, which
are least accessible for direct detection and accelerator searches.Comment: 10 pages, 5 figures; experimental sensitivities added to figure 2,
revised version to appear in Phys. Rev.
Models wagging the dog: are circuits constructed with disparate parameters?
In a recent article, Prinz, Bucher, and Marder (2004) addressed the fundamental question of whether neural systems are built with a fixed blueprint of tightly controlled parameters or in a way in which properties can vary largely from one individual to another, using a database modeling approach. Here, we examine the main conclusion that neural circuits indeed are built with largely varying parameters in the light of our own experimental and modeling observations. We critically discuss the experimental and theoretical evidence, including the general adequacy of database approaches for questions of this kind, and come to the conclusion that the last word for this fundamental question has not yet been spoken
Detecting high-frequency gravitational waves with optically-levitated sensors
We propose a tunable resonant sensor to detect gravitational waves in the
frequency range of 50-300 kHz using optically trapped and cooled dielectric
microspheres or micro-discs. The technique we describe can exceed the
sensitivity of laser-based gravitational wave observatories in this frequency
range, using an instrument of only a few percent of their size. Such a device
extends the search volume for gravitational wave sources above 100 kHz by 1 to
3 orders of magnitude, and could detect monochromatic gravitational radiation
from the annihilation of QCD axions in the cloud they form around stellar mass
black holes within our galaxy due to the superradiance effect.Comment: 5 pages, 2 figures, 2 tables, submitted to PRL -- v2: GR calculation
corrected, size of the signal and experimental geometry unaffected, cavity
response included in sensitivity plot and LIGO sensitivity curves update
Have Cherenkov telescopes detected a new light boson?
Recent observations by H.E.S.S. and MAGIC strongly suggest that the Universe
is more transparent to very-high-energy gamma rays than previously thought. We
show that this fact can be reconciled with standard blazar emission models
provided that photon oscillations into a very light Axion-Like Particle occur
in extragalactic magnetic fields. A quantitative estimate of this effect indeed
explains the observed data and in particular the spectrum of blazar 3C279.Comment: 3 pages, 1 figure, Proceeding of the "Eleventh International Workshop
on Topics in Astroparticle and Underground Physics" (TAUP), Roma, Italy, 1 -
5 July 2009 (to be published in the Proceedings
Electric Dipole Moments in Split Supersymmetry
We perform a quantitative study of the neutron and electron electric dipole
moments (EDM) in Supersymmetry, in the limit of heavy scalars. The leading
contributions arise at two loops. We give the complete analytic result,
including a new contribution associated with Z-Higgs exchange, which plays an
important and often leading role in the neutron EDM. The predictions for the
EDM are typically within the sensitivities of the next generation experiments.
We also analyse the correlation between the electron and neutron EDM, which
provides a robust test of Split Supersymmetry
One Loop Predictions of the Finely Tuned SSM
We study the finely tuned SSM, recently proposed by Arkani-Hamed and
Dimopoulos, at the one loop level. The runnings of the four gaugino Yukawa
couplings, the mu term, the gaugino masses, and the Higgs quartic coupling are
computed. The Higgs mass is found to be 130 - 170 GeV for M_s > 10^6 GeV. If
the Yukawa coupling constants are measured at the 1% level, this can determine
the SUSY breaking scale to within an order of magnitude. Measuring the
relationships between the couplings to this accuracy provides a striking signal
for this model.Comment: 5 pages, 4 figures; v2: Minor corrections to anomalous dimensions and
beta functions. Numerical results are not significantly affected. v3: Minor
changes to figures and references, as published in PR
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