224,528 research outputs found
Surplus Solid Angle as an Imprint of Horava-Lifshitz Gravity
We consider the electrostatic field of a point charge coupled to
Horava-Lifshitz gravity and find an exact solution describing the space with a
surplus (or deficit) solid angle. Although, theoretically in general
relativity, a surplus angle is hardly to be obtained in the presence of
ordinary matter with positive energy distribution, it seems natural in
Horava-Lifshitz gravity. We present the sudden disappearance and reappearance
of a star image as an astrophysical effect of a surplus angle. We also consider
matter configurations of all possible power law behaviors coupled to
Horava-Lifshitz gravity and obtain a series of exact solutions.Comment: 23 pages, 1 figure; minor changes, published versio
Density of Yang-Lee zeros for the Ising ferromagnet
The densities of Yang-Lee zeros for the Ising ferromagnet on the
square lattice are evaluated from the exact grand partition functions
(). The properties of the density of Yang-Lee zeros are discussed as
a function of temperature and system size . The three different classes
of phase transitions for the Ising ferromagnet, first-order phase transition,
second-order phase transition, and Yang-Lee edge singularity, are clearly
distinguished by estimating the magnetic scaling exponent from the
densities of zeros for finite-size systems. The divergence of the density of
zeros at Yang-Lee edge in high temperatures (Yang-Lee edge singularity), which
has been detected only by the series expansion until now for the square-lattice
Ising ferromagnet, is obtained from the finite-size data. The identification of
the orders of phase transitions in small systems is also discussed using the
density of Yang-Lee zeros.Comment: to appear in Physical Review
Verbal paired associates and the hippocampus: The role of scenes
It is widely agreed that patients with bilateral hippocampal damage are impaired at binding pairs of words together. Consequently, the verbal paired associates (VPA) task has become emblematic of hippocampal function. This VPA deficit is not well understood and is particularly difficult for hippocampal theories with a visuospatial bias to explain (e.g., cognitive map and scene construction theories). Resolving the tension among hippocampal theories concerning the VPA could be important for leveraging a fuller understanding of hippocampal function. Notably, VPA tasks typically use high imagery concrete words and so conflate imagery and binding. To determine why VPA engages the hippocampus, we devised an fMRI encoding task involving closely matched pairs of scene words, pairs of object words, and pairs of very low imagery abstract words. We found that the anterior hippocampus was engaged during processing of both scene and object word pairs in comparison to abstract word pairs, despite binding occurring in all conditions. This was also the case when just subsequently remembered stimuli were considered. Moreover, for object word pairs, fMRI activity patterns in anterior hippocampus were more similar to those for scene imagery than object imagery. This was especially evident in participants who were high imagery users and not in mid and low imagery users. Overall, our results show that hippocampal engagement during VPA, even when object word pairs are involved, seems to be evoked by scene imagery rather than binding. This may help to resolve the issue that visuospatial hippocampal theories have in accounting for verbal memory
Macroscopic quantum effects generated by the acoustic wave in a molecular magnet
We have shown that the size of the magnetization step due to resonant spin
tunneling in a molecular magnet can be strongly affected by sound. The
transverse acoustic wave can also generate macroscopic quantum beats of the
magnetization during the field sweep.Comment: 4 pages, 6 figure
Idiopathic CD4+ T-lymphocytopenia with cryptococcal meningitis: first case report from Cambodia.
We report on a patient with cryptococcal meningitis with CD4+ T-lymphocytopenia and no evidence of HIV infection
Brane gravity, massless bulk scalar and self-tuning of the cosmological constant
We show that a self-tuning mechanism of the cosmological constant could work
in 5D non-compact space-time with a symmetry in the presence of a
massless scalar field. The standard model matter fields live only on the 4D
brane. The change of vacuum energy on the brane (brane cosmological constant)
by, for instance, electroweak and QCD phase transitions, just gives rise to
dynamical shifts of the profiles of the background metric and the scalar field
in the extra dimension, keeping 4D space-time flat without any fine-tuning. To
avoid naked singularities in the bulk, the brane cosmological constant should
be negative. We introduce an additional brane-localized 4D Einstein-Hilbert
term so as to provide the observed 4D gravity with the non-compact extra
dimension. With a general form of brane-localized gravity term allowed by the
symmetries, the low energy Einstein gravity is successfully reproduced on the
brane at long distances. We show this phenomenon explicitly for the case of
vanishing bulk cosmological constant.Comment: 1+15 pages, no figure, Version to appear in PR
Dark Matters in Axino Gravitino Cosmology
It is suggested that the axino mass in the 1 MeV region and gravitino mass in
the eV region can provide an axino lifetime of order of the time of photon
decoupling. In this case, some undecayed axinos act like cold dark matters and
some axino decay products (gravitinos and hot axions) act like hot dark matters
at the time of galaxy formation.Comment: 9 pages, Late
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