195 research outputs found
Resonant tunneling and Fano resonance in quantum dots with electron-phonon interaction
We theoretically study the resonant tunneling and Fano resonance in quantum
dots with electron-phonon (e-ph) interaction. We examine the bias-voltage ()
dependence of the decoherence, using Keldysh Green function method and
perturbation with respect to the e-ph interaction. With optical phonons of
energy , only the elastic process takes place when , in
which electrons emit and absorb phonons virtually. The process suppresses the
resonant amplitude. When , the inelastic process is possible which
is accompanied by real emission of phonons. It results in the dephasing and
broadens the resonant width. The bias-voltage dependence of the decoherence
cannot be obtained by the canonical transformation method to consider the e-ph
interaction if its effect on the tunnel coupling is neglected. With acoustic
phonons, the asymmetric shape of the Fano resonance grows like a symmetric one
as the bias voltage increases, in qualitative accordance with experimental
results.Comment: 28 pages, 11 figure
Influence of target material impurities on physical results in relativistic heavy-ion collisions
This paper presents the studies on the influence of the target material
impurities on physical observables registered in heavy ion collisions collected
by fixed target experiments. It mainly concerns the measures of multiplicity
fluctuations which can be used to searches for critical point of strongly
interacting matter, e.g. in the {NA61/SHINE} fixed-target experiment at CERN
SPS. The elemental composition of the targets used in the NA61/SHINE experiment
was determined applying wavelength dispersive X-ray fluorescence (WDXRF)
technique. The influence of measured target impurities on multiplicity
distributions and scaled variance was estimated using simulation events. The
modification of the standard analysis was proposed to reduce this influence.Comment: 12 pages, 11 figure
Transport in metallic multi-island Coulomb blockade systems: A systematic perturbative expansion in the junction transparency
We study electronic transport through metallic multi-island Coulomb-blockade
systems. Based on a diagrammatic real-time approach, we develop a computer
algorithm that generates and calculates all transport contributions up to
second order in the tunnel-coupling strengths for arbitrary multi-island
systems. This comprises sequential and cotunneling, as well as terms
corresponding to a renormalization of charging energies and tunneling
conductances. Multi-island cotunneling processes with energy transfer between
different island are taken into account. To illustrate our approach we analyze
the current through an island in Coulomb blockade, that is electrostatically
coupled to a second island through which a large current is flowing. In this
regime both cotunneling processes involving one island only as well as
multi-island processes are important. The latter can be understood as
photon-assisted sequential tunneling in the blockaded island, where the photons
are provided by potential fluctuations due to sequential tunneling in the
second island. We compare results of our approach to a P(E)-theory for
photon-assisted tunneling in the weak coupling limit.Comment: 14 pages, 7 figures, published version; minor changes in Sec. IV
Prevention and extinguishment of fires involving hypergolic propellants Final report
Halon 1301 system effectiveness in prevention and extinguishment of hypergolic propellant fire
Josephson photonics with a two-mode superconducting circuit
We analyze the quantum dynamics of two electromagnetic oscillators coupled in series to a voltage-biased Josephson junction. When the applied voltage leads to a Josephson frequency across the junction which matches the sum of the two mode frequencies, tunneling Cooper pairs excite photons in both modes simultaneously leading to far-from-equilibrium states. These states display highly nonclassical features including strong antibunching, violation of Cauchy-Schwartz inequalities, and number squeezing. We obtain approximate analytic results for both the regimes of low and high photon occupancies which are supported by a full numerical treatment. The impact of asymmetries between the two modes is explored, revealing a pronounced enhancement of number squeezing when the modes are damped at different rates
Crossing of two Coulomb-Blockade Resonances
We investigate theoretically the transport of non--interacting electrons
through an Aharanov--Bohm (AB) interferometer with two quantum dots (QD)
embedded into its arms. In the Coulomb-blockade regime, transport through each
QD proceeds via a single resonance. The resonances are coupled through the arms
of the AB device but may also be coupled directly. In the framework of the
Landauer--Buttiker approach, we present expressions for the scattering matrix
which depend explicitly on the energies of the two resonances and on the AB
phase. We pay particular attention to the crossing of the two resonances.Comment: 15 pages, 1 figur
Aharonov-Bohm interferometry with quantum dots: scattering approach versus tunneling picture
We address the question of how to model electron transport through closed
Aharonov-Bohm interferometers which contain quantum dots. By explicitly
studying interferometers with one and two quantum dots, we establish the
connection between a tunneling-Hamiltonian formulation on the one hand and a
scattering-matrix approach on the other hand. We prove that, under certain
circumstances, both approaches are equivalent, i.e., both types of models can
describe the same experimental setups. Furthermore, we analyze how the
interplay of the Aharonov-Bohm phase and the orbital phase associated with the
lengths of the interferometers' arms affect transport properties.Comment: 8 pages, 8 figures, published versio
Aharonov-Bohm Effect for Parallel and T-shaped Double Quantum Dots
We investigate the Aharonov-Bohm (AB) effect for the double quantum dots in
the Kondo regime using the slave-boson mean-field approximation. In contrast to
the non-interacting case, where the AB oscillation generally has the period of
4 when the two-subring structure is formed via the interdot tunneling
, we find that the AB oscillation has the period of 2 in the Kondo
regime. Such effects appear for the double quantum dots close to the T-shaped
geometry even in the charge-fluctuation regime. These results follow from the
fact that the Kondo resonance is always fixed to the Fermi level irrespective
of the detailed structure of the bare dot-levels.Comment: 3 pages, 4 figures; minor change
Indirect Exchange Interaction between two Quantum Dots in an Aharonov-Bohm Ring
We investigate the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction between
two spins located at two quantum dots embedded in an Aharonov-Bohm (AB) ring.
In such a system the RKKY interaction, which oscillates as a function of the
distance between two local spins, is affected by the flux. For the case of the
ferromagnetic RKKY interaction, we find that the amplitude of AB oscillations
is enhanced by the Kondo correlations and an additional maximum appears at half
flux, where the interaction is switched off. For the case of the
antiferromagnetic RKKY interaction, we find that the phase of AB oscillations
is shifted by pi, which is attributed to the formation of a singlet state
between two spins for the flux value close to integer value of flux.Comment: 10 pages, 5 figure
Young people practicing martial arts and their perception of success
Background: The scientific framework for this study is the Humanistic Theory of Martial Arts that provides the specific language and definitions for Combat Sports/Martial Arts manifestations. Objective: The main aim was to describe the “perception of success” in groups in age 15-17, 11,11% girls and 88,89% boys involved in martial arts training. Participants ( n = 63) consisted of young martial artists from Poland and the United States. Methods: The instrument used for data collection was the Perception of Success Questionnaire (POSQ) (translated into Polish); Statistical analysis consisted of calculating the Spearman rank correlation for each pair of subgroups being analyzed a Coefficient of variation for comparison between the values of measurement. Results: 1) A weak correlation between the type of cultivated fighting style and the perceptions of success (Spearman rank correlation = ,35); 2) A moderate relationship between the US participants versus the Polish participants, and the perceptions of success (Spearman rank = ,69); and 3) A weak relationship between sex (as a gender) and the perceptions of success in the martial arts and combat sports (Spearman rank = ,34). Conclusions: This study concludes that the form or style of cultivated martial art or combat sport being practiced did not have a significant impact on the perception of success expressed by children and young people engaged in it
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