16,064 research outputs found
Electroweak lights from Dark Matter annihilations
The energy spectra of Standard Model particles originated from Dark Matter
annihilations can be significantly altered by the inclusion of electroweak
gauge boson radiation from the final state. A situation where this effect is
particularly important is when a Majorana Dark Matter particle annihilates into
two light fermions. This process is in p-wave and hence suppressed by the small
value of the relative velocity of the annihilating particles. The inclusion of
electroweak radiation eludes this suppression and opens up a potentially
sizeable s-wave contribution to the annihilation cross section. I will discuss
the impact of this effect on the fluxes of stable particles resulting from the
Dark Matter annihilations, which are relevant for Dark Matter indirect
searches.Comment: 4 pages, 2 figures. Contribution to the conference proceedings of
TAUP 2011, Munich - Germany (5-9 September 2011
Accuracy of a teleported trapped field state inside a single bimodal cavity
We propose a simplified scheme to teleport a superposition of coherent states
from one mode to another of the same bimodal lossy cavity. Based on current
experimental capabilities, we present a calculation of the fidelity that can be
achieved, demonstrating accurate teleportation if the mean photon number of
each mode is at most 1.5. Our scheme applies as well for teleportation of
coherent states from one mode of a cavity to another mode of a second cavity,
both cavities embedded in a common reservoir.Comment: 4 pages, 2 figures, in appreciation for publication in Physical
Review
The distribution of Omega_k from the scale-factor cutoff measure
Our universe may be contained in one among a diverging number of bubbles that
nucleate within an eternally inflating multiverse. A promising measure to
regulate the diverging spacetime volume of such a multiverse is the
scale-factor cutoff, one feature of which is bubbles are not rewarded for
having a longer duration of slow-roll inflation. Thus, depending on the
landscape distribution of the number of e-folds of inflation among bubbles like
ours, we might hope to measure spacetime curvature. We study a recently
proposed cartoon model of inflation in the landscape and find a reasonable
chance (about ten percent) that the curvature in our universe is well above the
value expected from cosmic variance. Anthropic selection does not strongly
select for curvature as small as is observed (relative somewhat larger values),
meaning the observational bound on curvature can be used to rule out landscape
models that typically give too little inflation.Comment: 14 pages, 7 figure
Kaon physics with the KLOE detector
In this paper we discuss the recent finalized analyses by the KLOE experiment
at DANE: the CPT and Lorentz invariance test with entangled pairs, and the precision measurement of the branching fraction of
the decay . We also present the
status of an ongoing analysis aiming to precisely measure the mass
From perfect to fractal transmission in spin chains
Perfect state transfer is possible in modulated spin chains, imperfections
however are likely to corrupt the state transfer. We study the robustness of
this quantum communication protocol in the presence of disorder both in the
exchange couplings between the spins and in the local magnetic field. The
degradation of the fidelity can be suitably expressed, as a function of the
level of imperfection and the length of the chain, in a scaling form. In
addition the time signal of fidelity becomes fractal. We further characterize
the state transfer by analyzing the spectral properties of the Hamiltonian of
the spin chain.Comment: 8 pages, 10 figures, published versio
Phase diagrams of charged colloidal rods: can a uniaxial charge distribution break chiral symmetry?
We construct phase diagrams for charged rodlike colloids within the
second-virial approximation as a function of rod concentration, salt
concentration, and colloidal charge. Besides the expected isotropic-nematic
transition, we also find parameter regimes with a coexistence between a nematic
and a second, more highly aligned nematic phase including an
isotropic-nematic-nematic triple point and a nematic-nematic critical point,
which can all be explained in terms of the twisting effect. We compute the
Frank elastic constants to see if the twist elastic constant can become
negative, which would indicate the possibility of a cholesteric phase
spontaneously forming. Although the twisting effect reduces the twist elastic
constant, we find that it always remains positive. In addition, we find that
for finite aspect-ratio rods the twist elastic constant is also always
positive, such that there is no evidence of chiral symmetry breaking due to a
uniaxial charge distribution.Comment: Added a reference to Sec. 4 and extended discussions in Secs. 4 and
7, results unchange
Theory of continuum percolation II. Mean field theory
I use a previously introduced mapping between the continuum percolation model
and the Potts fluid to derive a mean field theory of continuum percolation
systems. This is done by introducing a new variational principle, the basis of
which has to be taken, for now, as heuristic. The critical exponents obtained
are , and , which are identical with the mean
field exponents of lattice percolation. The critical density in this
approximation is \rho_c = 1/\ve where \ve = \int d \x \, p(\x) \{ \exp [-
v(\x)/kT] - 1 \}. p(\x) is the binding probability of two particles
separated by \x and v(\x) is their interaction potential.Comment: 25 pages, Late
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New emissive mononuclear copper (I) complex: Structural and photophysical characterization focusing on solvatochromism, rigidochromism and oxygen sensing in mesoporous solid matrix
Quantum limit of photothermal cooling
We study the problem of cooling a mechanical oscillator using the
photothermal (bolometric) force. Contrary to previous attempts to model this
system, we take into account the noise effects due to the granular nature of
photon absorption. This allows us to tackle the cooling problem down to the
noise dominated regime and to find reasonable estimates for the lowest
achievable phonon occupation in the cantilever
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