2,184 research outputs found
A review of Quantum Gravity at the Large Hadron Collider
The aim of this article is to review the recent developments in the
phenomenology of quantum gravity at the Large Hadron Collider. We shall pay
special attention to four-dimensional models which are able to lower the
reduced Planck mass to the TeV region and compare them to models with a large
extra-dimensional volume. We then turn our attention to reviewing the emission
of gravitons (massless or massive) at the LHC and to the production of small
quantum black holes.Comment: 32 pages, invited revie
On the Theory of Fermionic Preheating
In inflationary cosmology, the particles constituting the Universe are
created after inflation due to their interaction with moving inflaton field(s)
in the process of preheating. In the fermionic sector, the leading channel is
out-of equilibrium particle production in the non-perturbative regime of
parametric excitation, which respects Pauli blocking but differs significantly
from the perturbative expectation. We develop theory of fermionic preheating
coupling to the inflaton, without and with expansion of the universe, for light
and massive fermions, to calculate analytically the occupation number of
created fermions, focusing on their spectra and time evolution. In the case of
large resonant parameter we extend for rermions the method of successive
parabolic scattering, earlier developed for bosonic preheating. In an expanding
universe parametric excitation of fermions is stochastic. Created fermions very
quickly, within tens of inflaton oscillations, fill up a sphere of radius
in monetum space. We extend our formalism to the production of
superheavy fermions and to `instant' fermion creation.Comment: 14 pages, latex, 12 figures, submitted for publicatio
Anomaly mediated supersymmetry breaking and its test in linear colliders
Signatures of anomaly mediated supersymmetry breaking in linear colliders are
briefly reviewed after presenting an outline of the theoretical framework. A
unique and distinct feature of a large class of models of this type is a
winolike chargino which is very closely degenerate in mass with the lightest
neutralino. The very slow decay of this chargino results in a heavily ionizing
charged track and one soft charged pion with a characteristic momentum
distribution, leading to unique signals in linear colliders which are
essentially free of background. The determination of chargino and slepton
masses from such events is a distinctly interesting possibility.Comment: 15 pages, LaTex, 4 PS figures, ws-mpla.cls file included. One
reference added. To appear as a Brief Review in Modern Physics Letters
Hong-Ou-Mandel interference between independent III-V on silicon waveguide integrated lasers
The versatility of silicon photonic integrated circuits has led to a
widespread usage of this platform for quantum information based applications,
including Quantum Key Distribution (QKD). However, the integration of simple
high repetition rate photon sources is yet to be achieved. The use of
weak-coherent pulses (WCPs) could represent a viable solution. For example,
Measurement Device Independent QKD (MDI-QKD) envisions the use of WCPs to
distill a secret key immune to detector side channel attacks at large
distances. Thus, the integration of III-V lasers on silicon waveguides is an
interesting prospect for quantum photonics. Here, we report the experimental
observation of Hong-Ou-Mandel interference with 46\pm 2% visibility between
WCPs generated by two independent III-V on silicon waveguide integrated lasers.
This quantum interference effect is at the heart of many applications,
including MDI-QKD. Our work represents a substantial first step towards an
implementation of MDI-QKD fully integrated in silicon, and could be beneficial
for other applications such as standard QKD and novel quantum communication
protocols.Comment: 5 pages, 3 figure
Unstable Heavy Majorana Neutrinos and Leptogenesis
We propose a new mechanism producing a non-vanishing lepton number asymmetry,
based on decays of heavy Majorana neutrinos. If they are produced out of
equilibrium, as occurs in preheating scenario, and are superpositions of mass
eigenstates rapidly decaying, their decay rates contains interference terms
provided the mass differences are small compared to widths .
The resulting lepton asymmetry, which is the analogue of the time-integrated CP
asymmetry in system, is found to be proportional to .Comment: 18 pages, latex, revised version to be published in Phys. Rev.
Strategies to identify muscle fatigue from SEMG during cycling
Detection, quantification and analysis of muscle fatigue are crucial in occupational/rehabilitation and sporting settings. Sports organizations, such as the Australian Institute of Sports (AIS), currently monitor fatigue by a battery of tests including invasive techniques that require taking blood samples and/or muscle biopsies, the latter of which is highly invasive, painful, time consuming and expensive. SEMG (surface electromyography) is non-invasive monitoring of muscle activation and is an indication of localized muscle fatigue based on the observed shift of the power spectral density of the SEMG. The success of SEMG based techniques is currently limited to isometric contraction and is not acceptable to the human movement community. The paper proposes and tests a simple signal processing technique to identify the onset of muscle fatigue during cyclic activities of muscles, such as VL and VM, during cycling. Based on experiments conducted with 7 participants, using power output as a measure of fatigue, the technique is able to identify muscle fatigue with 98% significance
Sgoldstino events in top decays at LHC
We study top-quark decays in models with light sgoldstinos. The off-diagonal
entries in the squark mass matrices can lead to FCNC top two-body decays into
sgoldstinos and u(c) quarks. We compute the rates for these decays and discuss
the corresponding signatures that could manifest the presence of sgoldstinos in
top decays at LHC. We expect that a supersymmetry breaking scale up
to a scale of order 10 TeV could be probed through this process, for a maximal
squark mixing with the third generation. Justified by our preliminary analysis,
a thorough study of the corresponding signal versus background and systematics
in the LHC environment would be most welcome, in order to accurately assess the
potential of this promising process in determining .Comment: Standard LaTeX, 11 pages, 4 figures, one reference adde
Renormalization of the nonequilibrium dynamics of fermions in a flat FRW universe
We derive the renormalized equations of motion and the renormalized
energy-momentum tensor for fermions coupled to a spatially homogeneous scalar
field (inflaton) in a flat FRW geometry. The fermion back reaction to the
metric and to the inflaton field is formulated in one-loop approximation.
Having determined the infinite counter terms in an scheme we
formulate the finite terms in a form suitable for numerical computation. We
comment on the trace anomaly which is inferred from the standard analysis. We
also address the problem of initial singularities and determine the Bogoliubov
transformation by which they are removed.Comment: 26 pages, LaTe
E-SCAPE New tools and new opportunities for the localization of Expo 2015 general interest services along the Canale Cavour, a backbone of the Milan-Turin urban region
Publication of the Alta Scuola Politecnica project "E-SCAPE. New tools and new opportunities for the localization of Expo 2015 general interest services along the Canale Cavour, a backbone of the Milan-Turin urban region
Thermalization After Inflation and Reheating Temperature
We present a detailed examination of thermalization after inflation for
perturbative inflaton decay. Different interactions among particles in the
plasma of inflaton decay products are considered and it will be shown that 2 ->
2 scatterings and particle decay are the important ones. We show that
thermalization occurs after decays dominate scatterings, and that depending on
the typical mass scale of inflaton decay products, different situations may
arise. In particular, thermalization may be delayed until late times, in which
case the bounds from thermal gravitino production on supersymmetric models of
inflation are considerably relaxed. We will also consider the case where the
observable sector consists only of the MSSM matter content, and point out that
flat directions with large vevs may result in earlier thermalization of the
plasma and push the reheat temperature towards its upper limit.Comment: 18 pages, LaTeX, a few references added and revise
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