3,840 research outputs found
Gorkov equations for a pseudo-gapped high temperature superconductor
A theory of superconductivity based on the two-body Cooperon propagator is
presented. This theory takes the form of a modified Gorkov equation for the
Green's function and allows one to model the effect of local superconducting
correlations and long range phase fluctuations on the spectral properties of
high temperature superconductors, both above and below Tc. A model is proposed
for the Cooperon propagator, which provides a simple physical picture of the
pseudo-gap phenomenon, as well as new insights into the doping dependence of
the spectral properties. Numerical calculations of the density of states and
spectral functions based on this model are also presented, and compared with
the experimental STM and ARPES data. It is found, in particular, that the
sharpness of the peaks in the density of states is related to the strength and
the range of the superconducting correlations and that the apparent pseudo-gap
in STM and ARPES can be different, although the underlying model is the same.Comment: REVTEX 3.1, 8 pages, 5 EPS figures, submitted to Phys. Rev.
Bianchi type I universes with dilaton and magnetic fields
We consider the dynamics of a Bianchi type I spacetime in the presence of
dilaton and magnetic fields. The general solution of the Einstein-Maxwell
dilaton field equations can be obtained in an exact parametric form. Depending
on the numerical values of the parameters of the model there are three distinct
classes of solutions. The time evolution of the mean anisotropy, shear and
deceleration parameter is considered in detail and it is shown that a
magnetic-dilaton anisotropic Bianchi type I geometry does not isotropize, the
initial anisotropy being present in the universe for all times.Comment: 10 pages, 4 figure
Possible scenarios for soft and semi-hard components structure in central hadron-hadron collisions in the TeV region
Possible scenarios in hh collisions in the TeV regions are discussed in full
phase space. It is shown that at such high energies one should expect strong
KNO scaling violation and a ln(s) increase of the average charged multiplicity
of the semi-hard component, resulting in a huge mini-jet production.Comment: 20 pages, 9 PS figures included, LaTeX2e with AMSmath, epsfi
Clan structure analysis and new physics signals in pp collisions at LHC
The study of possible new physics signals in global event properties in pp
collisions in full phase space and in rapidity intervals accessible at LHC is
presented. The main characteristic is the presence of an elbow structure in
final charged particle MD's in addition to the shoulder observed at lower c.m.
energies.Comment: 9 pages, talk given at Focus on Multiplicity (Bari, Italy, June 2004
Diffuse radio emission from the Intracluster medium
An important aspect of the radio emission from galaxy clusters is represented
by the diffuse radio sources associated with the intracluster medium: radio
halos, relics and mini-halos. The radio halos and relics are indicators of
cluster mergers, whereas mini-halos are detected at the center of cooling core
clusters. SKA will dramatically improve the knowledge of these sources, thanks
to the detection of new objects, and to detailed studies of their spectra and
polarized emission. SKA will also provide the opportunity to investigate the
presence of halos produced by radiation scattered by a powerful radio galaxy at
the cluster centers.Comment: 8 pages, 6 figures, to appear in: "Science with the Square Kilometer
Array", eds. C. Carilli & S. Rawlings, New Astronomy Reviews, (Elsevier,
Amsterdam
Scenarios for multiplicity distributions in pp collisions in the TeV energy region
Possible scenarios based on available experimental data and phenomenological
knowledge of the GeV energy region are extended to the TeV energy region in the
framework of the weighted superposition mechanism of soft and semi-hard events.
KNO scaling violations, forward-backward multiplicity correlations, Hq vs. q
oscillations and shoulder structures are discussed.Comment: 10 pages, 10 figures, talk given at "Focus on Multiplicity" (Bari,
Italy, June 2004
Magnetic field induced non-Fermi liquid to Fermi liquid crossover at the quantum critical point of YbCuAu
The temperature (T) dependence of the muon and Cu nuclear spin-lattice
relaxation rates in YbCu4.4Au0.6 is reported over nearly four decades.
It is shown that for diverges following the behaviour
predicted by the self-consistent renormalization (SCR) theory developed by
Moriya for a ferromagnetic quantum critical point. On the other hand, the
static uniform susceptibility is observed to diverge as and
, a behaviour which is not accounted for by SCR theory.
The application of a magnetic field is observed to induce a crossover to a
Fermi liquid behaviour and for is found to obey the scaling
law .Comment: 4 pages, 4 figure
A Possible Case of Neurogenic Pulmonary Edema in a Sheep following Intracranial Surgery
A 3-year-old female crossbred sheep weighing 64 kg was anaesthetized for intracranial surgery as a part of a research project. Premedication and induction of anesthesia were uneventful as well as tracheal intubation. Anesthesia was maintained with isoflurane in a 50% mixture of oxygen and air, fentanyl (5-15 ”g kg-1h-1) and lidocaine (1.8 mg kg-1h-1). During anesthesia, an increased alveolar-arterial oxygen gradient was calculated on the basis of arterial blood gas analysis: inspiratory fraction of oxygen was increased and a recruitment manoeuvre was performed. After 210 minutes of anesthesia, the sheep was let recover with oxygen supplementation under monitoring of pulse-oxymetry, capnography, inspired and expired oxygen, temperature and invasive blood pressure. At tracheal extubation no signs of regurgitation or aspiration were noticed. Twenty-five minutes later, the sheep showed deterioration of neurological status and clonic seizure responsive to diazepam. After transient tachycardia, blood pressure rose acutely and sinus bradycardia followed. Severe tachypnea started in few minutes accompanied by loud respiratory noises and harsh diffuse crackles on both sides of the thorax. Foamy blood nasal exudates discharged from the nostrils. Neurogenic pulmonary edema as a sequel of increased intracranial pressure was suspected and treated with intravenous mannitol (0.5 gkg-1) and furosemide (4 mgKg-1). Hypoxemia was successfully managed with oxygen supplementation. Motor and cognitive functions improved progressively and were deemed normal within 12 hours from the episode, when arterial partial pressure of oxygen was 11.7 kPa (88 mmHg) at room air
e-EVN monitoring of M87
M87 is a privileged laboratory for a detailed study of the properties of jets, owing to its proximity (D=16.7 Mpc, 1 mas = 0.080 pc), its massive black hole (~6.0 x 10^9M) and its conspicuous emission at radio wavelengths and above. We started on November 2009 a monitoring program with the e-EVN at 5 GHz, in correspondence of the season of Very High Energy (VHE) observations. Indeed, two episodes of VHE activity have been reported in February and April 2010. We present here the main results of these multi-epoch observations: the inner jet and HST-1 are both detected and resolved in our datasets. We study the apparent velocity of HST-1, which seems to be increasing since 2005, and the flux density variability in the inner jet. All in all, the radio counterpart to this yearâs VHE event seems to be different from the ones in 2005 and 2008, opening new scenario for the radio-high energy connection
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