9,436 research outputs found
Doping and temperature dependence of electron spectrum and quasiparticle dispersion in doped bilayer cuprates
Within the t-t'-J model, the electron spectrum and quasiparticle dispersion
in doped bilayer cuprates in the normal state are discussed by considering the
bilayer interaction. It is shown that the bilayer interaction splits the
electron spectrum of doped bilayer cuprates into the bonding and antibonding
components around the point. The differentiation between the bonding
and antibonding components is essential, which leads to two main flat bands
around the point below the Fermi energy. In analogy to the doped
single layer cuprates, the lowest energy states in doped bilayer cuprates are
located at the point. Our results also show that the striking
behavior of the electronic structure in doped bilayer cuprates is intriguingly
related to the bilayer interaction together with strong coupling between the
electron quasiparticles and collective magnetic excitations.Comment: 9 pages, 4 figures, updated references, added figures and
discussions, accepted for publication in Phys. Rev.
Lagrange formalism of memory circuit elements: classical and quantum formulations
The general Lagrange-Euler formalism for the three memory circuit elements,
namely, memristive, memcapacitive, and meminductive systems, is introduced. In
addition, {\it mutual meminductance}, i.e. mutual inductance with a state
depending on the past evolution of the system, is defined. The Lagrange-Euler
formalism for a general circuit network, the related work-energy theorem, and
the generalized Joule's first law are also obtained. Examples of this formalism
applied to specific circuits are provided, and the corresponding Hamiltonian
and its quantization for the case of non-dissipative elements are discussed.
The notion of {\it memory quanta}, the quantum excitations of the memory
degrees of freedom, is presented. Specific examples are used to show that the
coupling between these quanta and the well-known charge quanta can lead to a
splitting of degenerate levels and to other experimentally observable quantum
effects
Harmonic emission from cluster nanoplasmas subject to intense short laser pulses
Harmonic emission from cluster nanoplasmas subject to short intense infrared
laser pulses is studied. In a previous publication [M. Kundu et al., Phys. Rev.
A 76, 033201 (2007)] we reported particle-in-cell simulation results showing
resonant enhancements of low-order harmonics when the Mie plasma frequency of
the ionizing and expanding cluster resonates with the respective harmonic
frequency. Simultaneously we found that high-order harmonics were barely
present in the spectrum, even at high intensities. The current paper is focused
on the analytical modeling of the process. We show that dynamical stochasticity
owing to nonlinear resonance inhibits the emission of high order harmonics.Comment: 12 pages, 7 figures, RevTe
The production rate of the coarse grained Gibbs entropy and the Kolmogorov-Sinai entropy: a real connection ?
We discuss the connection between the Kolmogorov-Sinai entropy, , and
the production rate of the coarse grained Gibbs entropy, . Detailed
numerical computations show that the (often accepted) identification of the two
quantities does not hold in systems with intermittent behavior and/or very
different characteristic times and in systems presenting pseudo-chaos. The
basic reason of this fact is in the asymptotic (with respect to time) nature of
, while is a quantity related to short time features of a system.Comment: 8 pages, 5 figures Submitted to PR
Time-dependent coupled oscillator model for charged particle motion in the presence of a time varyingmagnetic field
The dynamics of time-dependent coupled oscillator model for the charged
particle motion subjected to a time-dependent external magnetic field is
investigated. We used canonical transformation approach for the classical
treatment of the system, whereas unitary transformation approach is used when
managing the system in the framework of quantum mechanics. For both approaches,
the original system is transformed to a much more simple system that is the sum
of two independent harmonic oscillators which have time-dependent frequencies.
We therefore easily identified the wave functions in the transformed system
with the help of invariant operator of the system. The full wave functions in
the original system is derived from the inverse unitary transformation of the
wave functions associated to the transformed system.Comment: 16 page
Initial Hypersurface Formulation: Hamilton-Jacobi Theory for Strongly Coupled Gravitational Systems
Strongly coupled gravitational systems describe Einstein gravity and matter
in the limit that Newton's constant G is assumed to be very large. The
nonlinear evolution of these systems may be solved analytically in the
classical and semiclassical limits by employing a Green function analysis.
Using functional methods in a Hamilton-Jacobi setting, one may compute the
generating functional (`the phase of the wavefunctional') which satisfies both
the energy constraint and the momentum constraint. Previous results are
extended to encompass the imposition of an arbitrary initial hypersurface. A
Lagrange multiplier in the generating functional restricts the initial fields,
and also allows one to formulate the energy constraint on the initial
hypersurface. Classical evolution follows as a result of minimizing the
generating functional with respect to the initial fields. Examples are given
describing Einstein gravity interacting with either a dust field and/or a
scalar field. Green functions are explicitly determined for (1) gravity, dust,
a scalar field and a cosmological constant and (2) gravity and a scalar field
interacting with an exponential potential. This formalism is useful in solving
problems of cosmology and of gravitational collapse.Comment: 30 pages Latex (IOP) file with 2 IOP style files, to be published in
Classical and Quantum Gravity (1998
Entanglement Entropy of Fermi Liquids via Multi-dimensional Bosonization
The logarithmic violations of the area law, i.e. an "area law" with
logarithmic correction of the form , for entanglement
entropy are found in both 1D gapless system and for high dimensional free
fermions. The purpose of this work is to show that both violations are of the
same origin, and in the presence of Fermi liquid interactions such behavior
persists for 2D fermion systems. In this paper we first consider the
entanglement entropy of a toy model, namely a set of decoupled 1D chains of
free spinless fermions, to relate both violations in an intuitive way. We then
use multi-dimensional bosonization to re-derive the formula by Gioev and Klich
[Phys. Rev. Lett. 96, 100503 (2006)] for free fermions through a low-energy
effective Hamiltonian, and explicitly show the logarithmic corrections to the
area law in both cases share the same origin: the discontinuity at the Fermi
surface (points). In the presence of Fermi liquid (forward scattering)
interactions, the bosonized theory remains quadratic in terms of the original
local degrees of freedom, and after regularizing the theory with a mass term we
are able to calculate the entanglement entropy perturbatively up to second
order in powers of the coupling parameter for a special geometry via the
replica trick. We show that these interactions do not change the leading
scaling behavior for the entanglement entropy of a Fermi liquid. At higher
orders, we argue that this should remain true through a scaling analysis.Comment: 18 pages, accepted version with major updat
Realism about the Wave Function
A century after the discovery of quantum mechanics, the meaning of quantum
mechanics still remains elusive. This is largely due to the puzzling nature of
the wave function, the central object in quantum mechanics. If we are realists
about quantum mechanics, how should we understand the wave function? What does
it represent? What is its physical meaning? Answering these questions would
improve our understanding of what it means to be a realist about quantum
mechanics. In this survey article, I review and compare several realist
interpretations of the wave function. They fall into three categories:
ontological interpretations, nomological interpretations, and the \emph{sui
generis} interpretation. For simplicity, I will focus on non-relativistic
quantum mechanics.Comment: Penultimate version for Philosophy Compas
Simultaneous Dual Frequency Observations of Giant Pulses from the Crab Pulsar
Simultaneous measurements of giant pulses from the Crab pulsar were taken at
two widely spaced frequencies using the real-time detection of a giant pulse at
1.4 GHz at the Very Large Array to trigger the observation of that same pulse
at 0.6 GHz at a 25-m telescope in Green Bank, WV. Interstellar dispersion of
the signals provided the necessary time to communicate the trigger across the
country via the Internet. About 70% of the pulses are seen at both 1.4 GHz and
0.6 GHz, implying an emission mechanism bandwidth of at least 0.8 GHz at 1 GHz
for pulse structure on time scales of one to ten microseconds.
The arrival times at both frequencies display a jitter of 100 microseconds
within the window defined by the average main pulse profile and are tightly
correlated. This tight correlation places limits on both the emission mechanism
and on frequency dependent propagation within the magnetosphere.
At 1.4 GHz the giant pulses are resolved into several, closely spaced
components. Simultaneous observations at 1.4 GHz and 4.9 GHz show that the
component splitting is frequency independent. We conclude that the multiplicity
of components is intrinsic to the emission from the pulsar, and reject the
hypothesis that this is the result of multiple imaging as the signal propagates
through the perturbed thermal plasma in the surrounding nebula. At both 1.4 GHz
and 0.6 GHz the pulses are characterized by a fast rise time and an exponential
decay time which are correlated. The pulse broadening with its exponential
decay form is most likely the result of multipath propagation in intervening
ionized gas.Comment: LaTeX, 18 pages, 7 figures, accepted for publication in The
Astrophysical Journa
Bose-Einstein condensation in the presence of a uniform field and a point-like impurity
The behavior of an ideal -dimensional boson gas in the presence of a
uniform gravitational field is analyzed. It is explicitly shown that,
contrarily to an old standing folklore, the three-dimensional gas does not
undergo Bose-Einstein condensation at finite temperature. On the other hand,
Bose-Einstein condensation occurs at for if there is a
point-like impurity at the bottom of the vessel containing the gas.Comment: 14 pages, REVTEX. Revised version, accepted for publication in Phys.
Rev.
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