2,182 research outputs found
The mobility and diffusion of a particle coupled to a Luttinger liquid
We study the mobility of a particle coupled to a one dimensional interacting
fermionic system, a Luttinger liquid. We bosonize the Luttinger liquid and find
the effective interaction between the particle and the bosonic system. We show
that the dynamics of this system is completely equivalent to the acoustic
polaron problem where the interaction has purely electronic origin. This
problem has a zero mode excitation, or soliton, in the strong coupling limit
which corresponds to the formation of a polarization cloud due to the
fermion-fermion interaction around the particle. We obtain that, due to the
scattering of the residual bosonic modes, the soliton has a finite mobility and
diffusion coefficient at finite temperatures which depend on the
fermion-fermion interaction. We show that at low temperatures the mobility and
the diffusion coefficient are proportional to and respectively
and at high temperatures the mobility vanishes as while the diffusion
increases as .Comment: 9 pages, Revtex, UIUC preprin
Dissipative quantum systems modeled by a two level reservoir coupling
The coupling between a quantum dynamical system and a two-level system
reservoir is analysed within the framework of the Feynman-Vernon theory. We
stress the differences between this new reservoir and the well-known bath of
oscillators and show that, in order to obtain the Langevin equation for the
system of interest in the high temperature regime, we have to choose a spectral
distribution function which is finite for .Comment: 6 pages, RevteX, preprint UNICAM
Landau level bosonization of a 2D electron gas
In this work we introduce a bosonization scheme for the low energy
excitations of a 2D interacting electron gas in the presence of an uniform
magnetic field under conditions where a large integral number of Landau levels
are filled. We give an explicit construction for the electron operator in terms
of the bosons. We show that the elementary neutral excitations, known as the
magnetic excitons or magnetoplasma modes, can be described within a bosonic
language and that it provides a quadratic bosonic Hamiltonian for the
interacting electron system which can be easily diagonalized.Comment: 4 pages, revte
Tomography and geodynamics structure of the Ibero- Maghrebian region
The present study has two main goals: 1) use the most actual seismological data from recent earthquakes in the extended Alboran region to develop a geodynamic-structural model for the region through the application of seismic local tomography techniques; 2) modelling seismogenic sources using specific applications of analysis.
The structural scheme detailed in depth will allows us to define possible structural blocks in region between north of Morocco and Alboran sea. Currently the GPS studies show local movements in northern morocco independently of the general movement of the African plate.
The present tomographic study focuses on SW Ibero-Maghrebian region. The P and S arrival times at 52 stations located at north of Morocco (National Institute of Geophysics, CNRST, Rabat), south of Portugal (Instituto de Meteorologia, Lisbon) and Spain (Instituto Geografico National, Madrid) are used for the period between 12/1988 and 30/2008. We use a linearized inversion procedure to find a 3D velocity model for the studied region.
The resolution tests indicate that the calculated images give near true structure for the Tanger peninsula, the Alhoceima region and southern Spain at 5km depth. At 15, 30, 45 km depth we observe a near true structure in northern Morocco, and southern Spain. At 60 and 100 km, the southern Spain and SW of Alboran Sea gives a near true structure.
The resulting tomographic image shows that the total crustal thickness varies between 25 and 35 km and contains low-velocity anomalies. Is defined clearly a prominent negative P- wave velocity anomaly with a maximum decrease of approximately 6 per cent, at 15 km depth, in the northern Morocco. This low velocity demarcates a small bloc located between Iberia and African plate. This bloc is presented by a prominent high velocity anomaly that shows a maximum increase in P-wave velocity of approximately 6 per cent. The area with high velocity values could represent brittle and competent parts of the crust and lithosphere which sustain seismogenic stress where asperities along the faults could exist and probably more with the Iberia-Africa plate boundary.
Strong ground motions from major earthquakes depend strongly upon the 3D seismic velocity structure of the crust. Moreover the 3D velocity model is crucial for a better comprehension of structures behavior and has important practical applications toward understanding earthquake hazard in the Ibero-Maghrebian region. In particular, we hope to contribute, with this model, for seismic risk mitigation in north of Morocco
Minimal coupling method and the dissipative scalar field theory
Quantum field theory of a damped vibrating string as the simplest dissipative
scalar field investigated by its coupling with an infinit number of
Klein-Gordon fields as the environment by introducing a minimal coupling
method. Heisenberg equation containing a dissipative term proportional to
velocity obtained for a special choice of coupling function and quantum
dynamics for such a dissipative system investigated. Some kinematical relations
calculated by tracing out the environment degrees of freedom. The rate of
energy flowing between the system and it's environment obtained.Comment: 15 pages, no figur
Mobility of Bloch Walls via the Collective Coordinate Method
We have studied the problem of the dissipative motion of Bloch walls
considering a totally anisotropic one dimensional spin chain in the presence of
a magnetic field. Using the so-called "collective coordinate method" we
construct an effective Hamiltonian for the Bloch wall coupled to the magnetic
excitations of the system. It allows us to analyze the Brownian motion of the
wall in terms of the reflection coefficient of the effective potential felt by
the excitations due to the existence of the wall. We find that for finite
values of the external field the wall mobility is also finite. The spectrum of
the potential at large fields is investigated and the dependence of the damping
constant on temperature is evaluated. As a result we find the temperature and
magnetic field dependence of the wall mobility.Comment: 20 pages, 5 figure
Thrombus aspiration in patients with ST-elevation myocardial infarction: results of a national registry of interventional cardiology.
BACKGROUND:
We aimed to evaluate the impact of thrombus aspiration (TA) during primary percutaneous coronary intervention (P-PCI) in 'real-world' settings.
METHODS:
We performed a retrospective study, using data from the National Registry of Interventional Cardiology (RNCI 2006-2012, Portugal) with ST-elevation myocardial infarction (STEMI) patients treated with P-PCI. The primary outcome, in-hospital mortality, was analysed through adjusted odds ratio (aOR) and 95% confidence intervals (95%CI).
RESULTS:
We assessed data for 9458 STEMI patients that undergone P-PCI (35% treated with TA). The risk of in-hospital mortality with TA (aOR 0.93, 95%CI:0.54-1.60) was not significantly decreased. After matching patients through the propensity score, TA reduced significantly the risk of in-hospital mortality (OR 0.58, 95%CI:0.35-0.98; 3500 patients).
CONCLUSIONS:
The whole cohort data does not support the routine use of TA in P-PCI, but the results of the propensity-score matched cohort suggests that the use of selective TA may improve the short-term risks of STEMI.info:eu-repo/semantics/publishedVersio
Preferred Basis in a Measurement Process
The effect of decoherence is analysed for a free particle, interacting with
an environment via a dissipative coupling. The interaction between the particle
and the environment occurs by a coupling of the position operator of the
particle with the environmental degrees of freedom. By examining the exact
solution of the density matrix equation one finds that the density matrix
becomes completely diagonal in momentum with time while the position space
density matrix remains nonlocal. This establishes the momentum basis as the
emergent 'preferred basis' selected by the environment which is contrary to the
general expectation that position should emerge as the preferred basis since
the coupling with the environment is via the position coordinate.Comment: Standard REVTeX format, 10 pages of output. Accepted for publication
in Phys. Rev
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