326,666 research outputs found
Field Induced Positional Shift of Bloch Electrons and its Dynamical Implications
We derive the field correction to the Berry curvature of Bloch electrons,
which can be traced back to a positional shift due to the interband mixing
induced by external electromagnetic fields. The resulting semiclassical
dynamics is accurate to second order in the fields, in the same form as before,
provided that the wave packet energy is derived up to the same order. As
applications, we discuss the orbital magnetoelectric polarizability and predict
nonlinear anomalous Hall effects
Finite temperature effects on spin polarization of neutron matter in a strong magnetic field
Spin polarization of neutron matter at finite temperatures and strong
magnetic fields up to G is studied in the model with the Skyrme
effective interaction. It is shown that, together with the thermodynamically
stable branch of solutions for the spin polarization parameter corresponding to
the case when the majority of neutron spins are oriented opposite to the
direction of the magnetic field (negative spin polarization), the
self-consistent equations, beginning from some threshold density, have also two
other branches of solutions corresponding to positive spin polarization. The
influence of finite temperatures on spin polarization remains moderate in the
Skyrme model up to temperatures relevant for protoneutron stars, and, in
particular, the scenario with the metastable state characterized by positive
spin polarization, considered at zero temperature in Phys. Rev. C {\bf 80},
065801 (2009), is preserved at finite temperatures as well. It is shown that
above certain density the entropy for various branches of spin polarization in
neutron matter with the Skyrme interaction in a strong magnetic field
demonstrates the unusual behavior being larger than that of the nonpolarized
state. By providing the corresponding low-temperature analysis, it is clarified
that this unexpected behavior should be addressed to the dependence of the
entropy of a spin polarized state on the effective masses of neutrons with spin
up and spin down, and to a certain constraint on them which is violated in the
respective density range.Comment: Prepared with RevTeX4, 6pp., 4 figs; v2: accepted in JKA
Electron Spectral Functions of Reconstructed Quantum Hall Edges
During the reconstruction of the edge of a quantum Hall liquid, Coulomb
interaction energy is lowered through the change in the structure of the edge.
We use theory developed earlier by one of the authors [K. Yang, Phys. Rev.
Lett. 91, 036802 (2003)] to calculate the electron spectral functions of a
reconstructed edge, and study the consequences of the edge reconstruction for
the momentum-resolved tunneling into the edge. It is found that additional
excitation modes that appear after the reconstruction produce distinct features
in the energy and momentum dependence of the spectral function, which can be
used to detect the presence of edge reconstruction.Comment: RevTeX, 5 pages, 4 figures; replaced with the published version;
journal reference adde
Using Ancient Samples in Projection Analysis.
Projection analysis is a tool that extracts information from the joint allele frequency spectrum to better understand the relationship between two populations. In projection analysis, a test genome is compared to a set of genomes from a reference population. The projection's shape depends on the historical relationship of the test genome's population to the reference population. Here, we explore in greater depth the effects on the projection when ancient samples are included in the analysis. First, we conduct a series of simulations in which the ancient sample is directly ancestral to a present-day population (one-population model), or the ancient sample is ancestral to a sister population that diverged before the time of sampling (two-population model). We find that there are characteristic differences between the projections for the one-population and two-population models, which indicate that the projection can be used to determine whether a test genome is directly ancestral to a present-day population or not. Second, we compute projections for several published ancient genomes. We compare two Neanderthals and three ancient human genomes to European, Han Chinese and Yoruba reference panels. We use a previously constructed demographic model and insert these five ancient genomes to assess how well the observed projections are recovered
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