50,615 research outputs found
Coherent diffraction of thermal currents in Josephson tunnel junctions
We theoretically investigate heat transport in temperature-biased Josephson
tunnel junctions in the presence of an in-plane magnetic field. In full analogy
with the Josephson critical current, the phase-dependent component of the heat
flux through the junction displays coherent diffraction. Thermal transport is
analyzed in three prototypical junction geometries highlighting their main
differences. Notably, minimization of the Josephson coupling energy requires
the quantum phase difference across the junction to undergo \pi-slips in
suitable intervals of magnetic flux. An experimental setup suited to detect
thermal diffraction is proposed and analyzed.Comment: 6.5 pages, 4 color figures, updated versio
Excited-state quantum phase transitions in a two-fluid Lipkin model
Background: Composed systems have became of great interest in the framework
of the ground state quantum phase transitions (QPTs) and many of their
properties have been studied in detail. However, in these systems the study of
the so called excited-state quantum phase transitions (ESQPTs) have not
received so much attention.
Purpose: A quantum analysis of the ESQPTs in the two-fluid Lipkin model is
presented in this work. The study is performed through the Hamiltonian
diagonalization for selected values of the control parameters in order to cover
the most interesting regions of the system phase diagram. [Method:] A
Hamiltonian that resembles the consistent-Q Hamiltonian of the interacting
boson model (IBM) is diagonalized for selected values of the parameters and
properties such as the density of states, the Peres lattices, the
nearest-neighbor spacing distribution, and the participation ratio are
analyzed.
Results: An overview of the spectrum of the two-fluid Lipkin model for
selected positions in the phase diagram has been obtained. The location of the
excited-state quantum phase transition can be easily singled out with the Peres
lattice, with the nearest-neighbor spacing distribution, with Poincar\'e
sections or with the participation ratio.
Conclusions: This study completes the analysis of QPTs for the two-fluid
Lipkin model, extending the previous study to excited states. The ESQPT
signatures in composed systems behave in the same way as in single ones,
although the evidences of their presence can be sometimes blurred. The Peres
lattice turns out to be a convenient tool to look into the position of the
ESQPT and to define the concept of phase in the excited states realm
Copper(I)-Phosphinite Complexes in Click Cycloadditions: Three-Component Reactions and Preparation of 5-Iodotriazoles
© 2016 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.The remarkable activity displayed by copper(I)–phosphinite complexes of general formula [CuBr(L)] in two challenging cycloadditions is reported: a) the one-pot azidonation/cycloaddition of boronic acids, NaN3, and terminal alkynes; b) the cycloaddition of azides and iodoalkynes. These air-stable catalysts led to very good results in both cases and the expected triazoles could be isolated in pure form under ‘Click-suitable’ conditions
Clumpy Disc and Bulge Formation
We present a set of hydrodynamical/Nbody controlled simulations of isolated
gas rich galaxies that self-consistently include SN feedback and a detailed
chemical evolution model, both tested in cosmological simulations. The initial
conditions are motivated by the observed star forming galaxies at z ~ 2-3. We
find that the presence of a multiphase interstellar media in our models
promotes the growth of disc instability favouring the formation of clumps which
in general, are not easily disrupted on timescales compared to the migration
time. We show that stellar clumps migrate towards the central region and
contribute to form a classical-like bulge with a Sersic index, n > 2. Our
physically-motivated Supernova feedback has a mild influence on clump survival
and evolution, partially limiting the mass growth of clumps as the energy
released per Supernova event is increased, with the consequent flattening of
the bulge profile. This regulation does not prevent the building of a
classical-like bulge even for the most energetic feedback tested. Our Supernova
feedback model is able to establish a self-regulated star formation, producing
mass-loaded outflows and stellar age spreads comparable to observations. We
find that the bulge formation by clumps may coexit with other channels of bulge
assembly such as bar and mergers. Our results suggest that galactic bulges
could be interpreted as composite systems with structural components and
stellar populations storing archaeological information of the dynamical history
of their galaxy.Comment: Accepted for publication in MNRAS - Aug. 20, 201
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