357 research outputs found
Exact spin dynamics of the 1/r^2 supersymmetric t-J model in a magnetic field
The dynamical spin structure factor S^{zz}(Q,omega) in the small momentum
region is derived analytically for the one-dimensional supersymmetric t-J model
with 1/r^2 interaction. Strong spin-charge separation is found in the spin
dynamics. The structure factor S^{zz}(Q,omega) with a given spin polarization
does not depend on the electron density in the small momentum region. In the
thermodynamic limit, only two spinons and one antispinon (magnon) contribute to
S^{zz}(Q,omega). These results are derived via solution of the SU(2,1)
Sutherland model in the strong coupling limit.Comment: 20 pages, 8 figures. Accepted for publication in J.Phys.
Decoherence of Schrodinger cat states in a Luttinger liquid
Schrodinger cat states built from quantum superpositions of left or right
Luttinger fermions located at different positions in a spinless Luttinger
liquid are considered. Their decoherence rates are computed within the
bosonization approach using as environments the quantum electromagnetic field
or two or three dimensionnal acoustic phonon baths. Emphasis is put on the
differences between the electromagnetic and acoustic environments.Comment: 22 pages revtex4, 7 figures in a separate PS fil
Multiple EC power deposition locations tracking by break-in-slope analysis in TCV plasmas
Modulation of the amplitude of externally injected electron cyclotron (EC) power is a frequent method used to determine the radial power deposition profile in fusion plasmas. There are many tools to analyze the plasma response to the power modulations under quasi-stationary conditions. This paper focuses on the unique ability of the break-in-slope (BIS) method to retrieve a quasi-instantaneous estimate of the power deposition profile at each power step in the modulation, an outcome particularly relevant to track the power deposition location under non-stationary conditions. Here, the BIS analysis method is applied to the signals of a fast and high radial resolution wire-chamber soft x-ray camera in the Tokamak a Configuration Variable (TCV) where the plasma magnetic configuration and thus the EC resonance location are varied during the plasma discharge. As a step to validate this technique before real-time control experiments, the time-varying EC power deposition location of a single beam is successfully monitored by off-line BIS analysis. Simultaneous tracking of deposition locations of two EC beams gives promising results
Random bond XXZ chains with modulated couplings
The magnetization behavior of q-periodic antiferromagnetic spin 1/2
Heisenberg chains under uniform magnetic fields is investigated in a background
of disorder exchange distributions. By means of both real space decimation
procedures and numerical diagonalizations in XX chains, it is found that for
binary disorder the magnetization exhibits wide plateaux at values of
1+2(p-1)/q, where p is the disorder strength. In contrast, no spin gaps are
observed in the presence of continuous exchange distributions. We also study
the magnetic susceptibility at low magnetic fields. For odd q-modulations the
susceptibility exhibits a universal singularity, whereas for q even it displays
a non-universal power law behavior depending on the parameters of the
distribution.Comment: 4 pages, 3 figures. Final version to appear in PR
Crossed Andreev reflection at ferromagnetic domain walls
We investigate several factors controlling the physics of hybrid structures
involving ferromagnetic domain walls (DWs) and superconducting (S) metals. We
discuss the role of non collinear magnetizations in S/DW junctions in a spin
Nambu Keldysh formalism. We discuss transport in S/DW/N and
S/DW/S junctions in the presence of inelastic scattering in the domain wall. In
this case transport properties are similar for the S/DW/S and S/DW/N junctions
and are controlled by sequential tunneling of spatially separated Cooper pairs
across the domain wall. In the absence of inelastic scattering we find that a
Josephson current circulates only if the size of the ferromagnetic region is
smaller than the elastic mean free path meaning that the Josephson effect
associated to crossed Andreev reflection cannot be observed under usual
experimental conditions. Nevertheless a finite dc current can circulate across
the S/DW/S junction due to crossed Andreev reflection associated to sequential
tunneling.Comment: 18 pages, 8 figures, references added at the end of the introductio
Magnetic fluctuations in the classical XY model: the origin of an exponential tail in a complex system
We study the probability density function for the fluctuations of the
magnetic order parameter in the low temperature phase of the XY model of finite
size. In two-dimensions this system is critical over the whole of the low
temperature phase. It is shown analytically and without recourse to the scaling
hypothesis that, in this case, the distribution is non-Gaussian and of
universal form, independent of both system size and critical exponent .
An exact expression for the generating function of the distribution is
obtained, which is transformed and compared with numerical data from high
resolution molecular dynamics and Monte Carlo simulations. The calculation is
extended to general dimension and an exponential tail is found in all
dimensions less than four, despite the fact that critical fluctuations are
limited to D=2. These results are discussed in the light of similar behaviour
observed in models of interface growth and for dissipative systems driven into
a non-equilibrium steady state.Comment: 32 pages, 13 figures, 1 table. Few changes. To appear in Phys. Rev.
Influence of plasma turbulence on microwave propagation
It is not fully understood how electromagnetic waves propagate through plasma
density fluctuations when the size of the fluctuations is comparable with the
wavelength of the incident radiation. In this paper, the perturbing effect of a
turbulent plasma density layer on a traversing microwave beam is simulated with
full-wave simulations. The deterioration of the microwave beam is calculated as
a function of the characteristic turbulence structure size, the turbulence
amplitude, the depth of the interaction zone and the size of the waist of the
incident beam. The maximum scattering is observed for a structure size on the
order of half the vacuum wavelength. The scattering and beam broadening was
found to increase linearly with the depth of the turbulence layer and
quadratically with the fluctuation strength. Consequences for experiments and
3D effects are considered.Comment: 16 pages, 13 figures. This is an author-created, un-copyedited
version of an article submitted for publication in Plasma Physics and
Controlled Fusion. IoP Publishing Ltd is not responsible for any errors or
omissions in this version of the manuscript or any version derived from i
Evaporation kinetics in swollen porous polymeric networks
Ponencia presentada en el Congreso Euromar 2014.Fil: Velasco, Manuel Isaac. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Instituto de FĂsica Enrique Gaviola; Argentina.Fil: Silletta, Emilia Victoria. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Instituto de FĂsica Enrique Gaviola; Argentina.Fil: Monti, Gustavo Alberto. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Instituto de FĂsica Enrique Gaviola; Argentina.Fil: Acosta, Rodolfo HĂ©ctor. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Instituto de FĂsica Enrique Gaviola; Argentina.Fil: Velasco, Manuel Isaac. Universidad Nacional de CĂłrdoba. Facultad de Matemática, AstronomĂa y FĂsica; Argentina.Fil: Silletta, Emilia Victoria. Universidad Nacional de CĂłrdoba. Facultad de Matemática, AstronomĂa y FĂsica; Argentina.Fil: Monti, Gustavo Alberto. Universidad Nacional de CĂłrdoba. Facultad de Matemática, AstronomĂa y FĂsica; Argentina.Fil: Acosta, Rodolfo HĂ©ctor. Universidad Nacional de CĂłrdoba. Facultad de Matemática, AstronomĂa y FĂsica; Argentina.Fil: Gomez, Cesar Gerardo. Universidad Nacional de CĂłrdoba. Facultad de Ciencias QuĂmicas. Departamento de QuĂmica Orgánica; Argentina.Fil: Strumia, Miriam Cristina. Universidad Nacional de CĂłrdoba. Facultad de Ciencias QuĂmicas. Departamento de QuĂmica Orgánica; Argentina.Fil: Gomez, Cesar Gerardo. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Instituto Multidisciplinario de BiologĂa Vegetal; Argentina.Fil: Gomez, Cesar Gerardo. Universidad Nacional de CĂłrdoba. Instituto Multidisciplinario de BiologĂa Vegetal; Argentina.Fil: Strumia, Miriam Cristina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Instituto Multidisciplinario de BiologĂa Vegetal; Argentina.Fil: Strumia, Miriam Cristina. Universidad Nacional de CĂłrdoba. Instituto Multidisciplinario de BiologĂa Vegetal; Argentina.Polymer matrices with well defined structure and pore sizes are widely used in several areas of chemistry such as catalysis, enzyme immobilization, HPLC, adsorbents or controlled drug release. These polymers have pores in its structure both in the dry and swollen state. Although it is well known that the structures and properties greatly differ between these two states, only few methods provide information about the swollen one, even though most of the applications involve the matrices in this situation. Nuclear Magnetic Resonance (NMR) is a suitable tool for the study of the molecular dynamics of different liquids spatially confined in macro, meso and nanopores, through changes in the relaxation times. In transverse relaxation experiments, either diffusion inside the pore, or relaxation induced by mobility restriction of the liquid near the wall, are additional
sources of relaxation, which are extremely useful in the determination of structural and functional properties.Fil: Velasco, Manuel Isaac. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Instituto de FĂsica Enrique Gaviola; Argentina.Fil: Silletta, Emilia Victoria. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Instituto de FĂsica Enrique Gaviola; Argentina.Fil: Monti, Gustavo Alberto. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Instituto de FĂsica Enrique Gaviola; Argentina.Fil: Acosta, Rodolfo HĂ©ctor. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Instituto de FĂsica Enrique Gaviola; Argentina.Fil: Velasco, Manuel Isaac. Universidad Nacional de CĂłrdoba. Facultad de Matemática, AstronomĂa y FĂsica; Argentina.Fil: Silletta, Emilia Victoria. Universidad Nacional de CĂłrdoba. Facultad de Matemática, AstronomĂa y FĂsica; Argentina.Fil: Monti, Gustavo Alberto. Universidad Nacional de CĂłrdoba. Facultad de Matemática, AstronomĂa y FĂsica; Argentina.Fil: Acosta, Rodolfo HĂ©ctor. Universidad Nacional de CĂłrdoba. Facultad de Matemática, AstronomĂa y FĂsica; Argentina.Fil: Gomez, Cesar Gerardo. Universidad Nacional de CĂłrdoba. Facultad de Ciencias QuĂmicas. Departamento de QuĂmica Orgánica; Argentina.Fil: Strumia, Miriam Cristina. Universidad Nacional de CĂłrdoba. Facultad de Ciencias QuĂmicas. Departamento de QuĂmica Orgánica; Argentina.Fil: Gomez, Cesar Gerardo. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Instituto Multidisciplinario de BiologĂa Vegetal; Argentina.Fil: Gomez, Cesar Gerardo. Universidad Nacional de CĂłrdoba. Instituto Multidisciplinario de BiologĂa Vegetal; Argentina.Fil: Strumia, Miriam Cristina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Instituto Multidisciplinario de BiologĂa Vegetal; Argentina.Fil: Strumia, Miriam Cristina. Universidad Nacional de CĂłrdoba. Instituto Multidisciplinario de BiologĂa Vegetal; Argentina.FĂsica de los Materiales Condensado
Modelling of the effect of ELMs on fuel retention at the bulk W divertor of JET
Effect of ELMs on fuel retention at the bulk W target of JET ITER-Like Wall was studied with multi-scale calculations. Plasma input parameters were taken from ELMy H-mode plasma experiment. The energetic intra-ELM fuel particles get implanted and create near-surface defects up to depths of few tens of nm, which act as the main fuel trapping sites during ELMs. Clustering of implantation-induced vacancies were found to take place. The incoming flux of inter-ELM plasma particles increases the different filling levels of trapped fuel in defects. The temperature increase of the W target during the pulse increases the fuel detrapping rate. The inter-ELM fuel particle flux refills the partially emptied trapping sites and fills new sites. This leads to a competing effect on the retention and release rates of the implanted particles. At high temperatures the main retention appeared in larger vacancy clusters due to increased clustering rate
- …