1,590 research outputs found
New method for the quantum ground states in one dimension
A simple, general and practically exact method is developed to calculate the
ground states of 1D macroscopic quantum systems with translational symmetry.
Applied to the Hubbard model, a modest calculation reproduces the Bethe Ansatz
results
New method for the 3D Ising model
A simple, general and practically exact method is developed for the
equilibrium properties of the macroscopic physical systems with translational
symmetry. Applied to the Ising model in two and three dimension, a modest
calculation gives the spontaneous magnetization and the specific heat to less
than 1% error
Entanglement perturbation theory for the quantum ground states in two dimensions
A simple, general and practically exact method, Entanglement Perturbation
Theory (EPT), is formulated to calculate the ground states of 2D macroscopic
quantum systems with translational symmetry. An emphasis will be placed on the
applicability of EPT to fermions. We will discuss some preliminary evidences
which indicate a potential of EPT
Light propagation in non-trivial QED vacua
Within the framework of effective action QED, we derive the light cone
condition for homogeneous non-trivial QED vacua in the geometric optics
approximation. Our result generalizes the ``unified formula'' suggested by
Latorre, Pascual and Tarrach and allows for the calculation of velocity shifts
and refractive indices for soft photons travelling through these vacua.
Furthermore, we clarify the connection between the light velocity shift and the
scale anomaly. This study motivates the introduction of a so-called effective
action charge that characterizes the velocity modifying properties of the
vacuum. Several applications are given concerning vacuum modifications caused
by, e.g., strong fields, Casimir systems and high temperature.Comment: 13 pages, REVTeX, 3 figures, to appear in Phys. Rev.
Varied Signature Splitting Phenomena in Odd Proton Nuclei
Varied signature splitting phenomena in odd proton rare earth nuclei are
investigated. Signature splitting as functions of and in the angular
momentum projection theory is explicitly shown and compared with those of the
particle rotor model. The observed deviations from these rules are due to the
band mixings. The recently measured Ta high spin data are taken as a
typical example where fruitful information about signature effects can be
extracted. Six bands, two of which have not yet been observed, were calculated
and discussed in detail in this paper. The experimentally unknown band head
energies are given
Probing the shape of atoms in real space
The structure of single atoms in real space is investigated by scanning
tunneling microscopy. Very high resolution is possible by a dramatic reduction
of the tip-sample distance. The instabilities which are normally encountered
when using small tip-sample distances are avoided by oscillating the tip of the
scanning tunneling microscope vertically with respect to the sample. The
surface atoms of Si(111)-(7 x 7) with their well-known electronic configuration
are used to image individual samarium, cobalt, iron and silicon atoms. The
resulting images resemble the charge density corresponding to 4f, 3d and 3p
atomic orbitals.Comment: Submitted to Phys. Rev. B, 17 pages, 7 figure
Cumulative hydropathic topology of a voltage-gated sodium channel at atomic resolution
Voltage-gated sodium channels (NavChs) are biological pores that control the ow of sodium ions through the cell membrane. In humans, mutations in genes encoding NavChs can disrupt physiological cellular activity thus leading to a wide spectrum of diseases. Here, we present a topological connection between the functional architecture of a NavAb bacterial channel and accumulation of atomic hydropathicity around its pore. This connection is established via a scaling analysis methodology that elucidates how intrachannel hydropathic density variations translate into hydropathic dipole field configurations along the pore. Our findings suggest the existence of a non random cumulative hydropathic topology that is organized parallel to the membrane surface so that pore's stability, as well as, gating behavior are guaranteed. Given the biophysical significance of the hydropathic effect, our study seeks to provide a computational framework for studying cumulative hydropathic topological properties of NavChs and pore-forming proteins in general. This article is protected by copyright. All rights reserved
Anomalous Crossing Frequency in Odd Proton Nuclei
A generic explanation for the recently observed anomalous crossing
frequencies in odd proton rare earth nuclei is given. As an example, the proton
band in Ta is discussed in detail by using the
angular momentum projection theory. It is shown that the quadrupole pairing
interaction is decisive in delaying the crossing point and the changes in
crossing frequency along the isotope chain are due to the different neutron
shell fillings
Wave function mapping conditions in Open Quantum Dots structures
We discuss the minimal conditions for wave function spectroscopy, in which
resonant tunneling is the measurement tool. Two systems are addressed: resonant
tunneling diodes, as a toy model, and open quantum dots. The toy model is used
to analyze the crucial tunning between the necessary resolution in
current-voltage characteristics and the breakdown of the wave functions probing
potentials into a level splitting characteristic of double quantum wells. The
present results establish a parameter region where the wavefunction
spectroscopy by resonant tunneling could be achieved. In the case of open
quantum dots, a breakdown of the mapping condition is related to a change into
a double quantum dot structure induced by the local probing potential. The
analogy between the toy model and open quantum dots show that a precise control
over shape and extention of the potential probes is irrelevant for wave
function mapping. Moreover, the present system is a realization of a tunable
Fano system in the wave function mapping regime.Comment: 6 pages, 6 figure
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