10,222 research outputs found
Quantum quench dynamics of the Coulomb Luttinger model
We study the non-equilibrium dynamics of the Luttinger model after suddenly
turning on and off the bare Coulomb interaction between the fermions. We
analyze several correlation functions such as the one particle density matrix
and vertex correlations, its finite time dynamics and the stationary state
limit. Correlations exhibit a non-linear light cone effect: the spreading of
the initial signal accelerates as a consequence of the quantum nature of the
excitations, whose peculiar dispersion of plasmonic type in 1D gives rise to a
logarithmic divergence in the group velocity at . In addition we show that
both the static and dynamic stationary state correlations can be reproduced
with a simple generalised Gibbs ensemble despite the long-range character of
the interactions which precludes the application of the Lieb-Robinson bounds.
We propose a suitable experimental setup in which these effect can be observed
based on ultracold ions loaded on linear traps.Comment: 13 pages, 7 figure
Equations of Motion for the Out-of-Equilibrium Dynamics of Isolated Quantum Systems from the Projection Operator Technique
We present a rigorous framework to obtain evolution equations for the
momentum distribution and higher order correlation functions in weakly
interacting systems based on the Projection Operator Technique. These equations
can be numerically solved in an efficient way. We compare the solution of the
equations with known results for 1D models and find an excellent agreement.Comment: 6 pages, 1 figure, added brief discussion about the validity of the
approximation
Proof-of-principle of a new geometry for sampling calorimetry using inorganic scintillator plates
A novel geometry for a sampling calorimeter employing inorganic scintillators
as an active medium is presented. To overcome the mechanical challenges of
construction, an innovative light collection geometry has been pioneered, that
minimises the complexity of construction. First test results are presented,
demonstrating a successful signal extraction. The geometry consists of a
sampling calorimeter with passive absorber layers interleaved with layers of an
active medium made of inorganic scintillating crystals. Wavelength-shifting
(WLS) fibres run along the four long, chamfered edges of the stack,
transporting the light to photodetectors at the rear. To maximise the amount of
scintillation light reaching the WLS fibres, the scintillator chamfers are
depolished. It is shown herein that this concept is working for cerium fluoride
(CeF) as a scintillator. Coupled to it, several different types of
materials have been tested as WLS medium. In particular, materials that might
be sufficiently resistant to the High-Luminosity Large Hadron Collider
radiation environment, such as cerium-doped Lutetium-Yttrium Orthosilicate
(LYSO) and cerium-doped quartz, are compared to conventional plastic WLS
fibres. Finally, an outlook is presented on the possible optimisation of the
different components, and the construction and commissioning of a full
calorimeter cell prototype is presented.Comment: Submitted to Proceedings CALOR 2014, the 16th International
Conference on Calorimetry in High-Energy Physics, Giessen (Germany) 6 - 11
April 2014. To be published in Journal of Physics: Conference Series (10
pages, 15 figures
Proposal for SPS beam time for the baby MIND and TASD neutrino detector prototypes
The design, construction and testing of neutrino detector prototypes at CERN
are ongoing activities. This document reports on the design of solid state baby
MIND and TASD detector prototypes and outlines requirements for a test beam at
CERN to test these, tentatively planned on the H8 beamline in the North Area,
which is equipped with a large aperture magnet. The current proposal is
submitted to be considered in light of the recently approved projects related
to neutrino activities with the SPS in the North Area in the medium term
2015-2020
On the Regularity of Optimal Transportation Potentials on Round Spheres
In this paper the regularity of optimal transportation potentials defined on
round spheres is investigated. Specifically, this research generalises the
calculations done by Loeper, where he showed that the strong (A3) condition of
Trudinger and Wang is satisfied on the round sphere, when the cost-function is
the geodesic distance squared. In order to generalise Loeper's calculation to a
broader class of cost-functions, the (A3) condition is reformulated via a
stereographic projection that maps charts of the sphere into Euclidean space.
This reformulation subsequently allows one to verify the (A3) condition for any
case where the cost-fuction of the associated optimal transportation problem
can be expressed as a function of the geodesic distance between points on a
round sphere. With this, several examples of such cost-functions are then
analysed to see whether or not they satisfy this (A3) condition.Comment: 24 pages, 4 figure
Ultrastructure of STH cells of the pars distalis of hepatectomized mice
An electron microscopic analysis was performed on the pars distalis of the hypophysis of hepatectomized mice. Intact and sham operated mice served as controls. The STH cells presented striking changes that were most intense and widespread in those animals sacrificed at midnight of the second day after hepatectomy. These changes can be summarized as follows: 1) Hypertrophy of the Golgi complex with increased number of immature granules within the Golgi zone. This change appeared also in otherwise unmodified STH cells. 2) Strong dilatation of the endoplasmic reticulum whose cisternae contained much electron dense material. 3) Granules with partially diminished electron density, some of them in spatial relation with the plasma membrane and others swelling and bursting within the cytoplasm. All transitions between unchanged 350–400 mμ granules and extremely altered ones, were seen. 4) Release sites, characterized by dense zones in the plasmalemma, close to aggregates of electron lucent microvesicles, and almost empty granule membranes. 5) Increase in the density of the mitochondria which appeared grouped near the Golgi zone. 6) Increase in the number of large lysosomes of the autophagic vacuole type. 7) Irregular nuclear outlines. These data suggest increased synthesis and release of growth hormone in STH cells stimulated by hepatectomy.Facultad de Ciencias Médica
Test beam measurement of the first prototype of the fast silicon pixel monolithic detector for the TT-PET project
The TT-PET collaboration is developing a PET scanner for small animals with
30 ps time-of-flight resolution and sub-millimetre 3D detection granularity.
The sensitive element of the scanner is a monolithic silicon pixel detector
based on state-of-the-art SiGe BiCMOS technology. The first ASIC prototype for
the TT-PET was produced and tested in the laboratory and with minimum ionizing
particles. The electronics exhibit an equivalent noise charge below 600 e- RMS
and a pulse rise time of less than 2 ns, in accordance with the simulations.
The pixels with a capacitance of 0.8 pF were measured to have a detection
efficiency greater than 99% and, although in the absence of the
post-processing, a time resolution of approximately 200 ps
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