2,067 research outputs found
Hawking radiation as tunneling from squashed Kaluza-Klein black hole
We discuss Hawking radiation from a five-dimensional squashed Kaluza-Klein
black hole on the basis of the tunneling mechanism. A simple manner, which was
recently suggested by Umetsu, is possible to extend the original derivation by
Parikh and Wilczek to various black holes. That is, we use the two-dimensional
effective metric, which is obtained by the dimensional reduction near the
horizon, as the background metric. By using same manner, we derive both the
desired result of the Hawking temperature and the effect of the back reaction
associated with the radiation in the squashed Kaluza-Klein black hole
background.Comment: 16 page
Disruption of Drosophila melanogaster Lipid Metabolism Genes Causes Tissue Overgrowth Associated with Altered Developmental Signaling.
Developmental patterning requires the precise interplay of numerous intercellular signaling pathways to ensure that cells are properly specified during tissue formation and organogenesis. The spatiotemporal function of many developmental pathways is strongly influenced by the biosynthesis and intracellular trafficking of signaling components. Receptors and ligands must be trafficked to the cell surface where they interact, and their subsequent endocytic internalization and endosomal trafficking is critical for both signal propagation and its down-modulation. In a forward genetic screen for mutations that alter intracellular Notch receptor trafficking in Drosophila melanogaster, we recovered mutants that disrupt genes encoding serine palmitoyltransferase and acetyl-CoA carboxylase. Both mutants cause Notch, Wingless, the Epidermal Growth Factor Receptor (EFGR), and Patched to accumulate abnormally in endosomal compartments. In mosaic animals, mutant tissues exhibit an unusual non-cell-autonomous effect whereby mutant cells are functionally rescued by secreted activities emanating from adjacent wildtype tissue. Strikingly, both mutants display prominent tissue overgrowth phenotypes that are partially attributable to altered Notch and Wnt signaling. Our analysis of the mutants demonstrates genetic links between abnormal lipid metabolism, perturbations in developmental signaling, and aberrant cell proliferation
Free field approach to diagonalization of boundary transfer matrix : recent advances
We diagonalize infinitely many commuting operators . We call these
operators the boundary transfer matrix associated with the quantum
group and the elliptic quantum group. The boundary transfer matrix is related
to the solvable model with a boundary. When we diagonalize the boundary
transfer matrix, we can calculate the correlation functions for the solvable
model with a boundary. We review the free field approach to diagonalization of
the boundary transfer matrix associated with and
. We construct the free field realizations of the
eigenvectors of the boundary transfer matrix . This paper includes new
unpublished formula of the eigenvector for . It is thought that
this diagonalization method can be extended to more general quantum group
and elliptic quantum group .Comment: To appear in Group 28 : Group Theoretical Method in Physic
Exact one-periodic and two-periodic wave solutions to Hirota bilinear equations in 2+1 dimensions
Riemann theta functions are used to construct one-periodic and two-periodic
wave solutions to a class of (2+1)-dimensional Hirota bilinear equations. The
basis for the involved solution analysis is the Hirota bilinear formulation,
and the particular dependence of the equations on independent variables
guarantees the existence of one-periodic and two-periodic wave solutions
involving an arbitrary purely imaginary Riemann matrix. The resulting theory is
applied to two nonlinear equations possessing Hirota bilinear forms:
and
where , thereby yielding their one-periodic and two-periodic wave
solutions describing one dimensional propagation of waves
A direct method of solution for the Fokas-Lenells derivative nonlinear Schr\"odinger equation: I. Bright soliton solutions
We develop a direct method of solution for finding the bright -soliton
solution of the Fokas-Lenells derivative nonlinear Schr\"odinger equation. The
construction of the solution is performed by means of a purely algebraic
procedure using an elementary theory of determinants and does not rely on the
inverse scattering transform method. We present two different expressions of
the solution both of which are expressed as a ratio of determinants. We then
investigate the properties of the solutions and find several new features.
Specifically, we derive the formula for the phase shift caused by the
collisions of bright solitons.Comment: To appear in J. Phys. A: Math. Theor. 45(2012) Ma
Ultrashort pulses and short-pulse equations in dimensions
In this paper, we derive and study two versions of the short pulse equation
(SPE) in dimensions. Using Maxwell's equations as a starting point, and
suitable Kramers-Kronig formulas for the permittivity and permeability of the
medium, which are relevant, e.g., to left-handed metamaterials and dielectric
slab waveguides, we employ a multiple scales technique to obtain the relevant
models. General properties of the resulting -dimensional SPEs, including
fundamental conservation laws, as well as the Lagrangian and Hamiltonian
structure and numerical simulations for one- and two-dimensional initial data,
are presented. Ultrashort 1D breathers appear to be fairly robust, while rather
general two-dimensional localized initial conditions are transformed into
quasi-one-dimensional dispersing waveforms
Charge ordering in the spinels AlVO and LiVO
We develop a microscopic theory for the charge ordering (CO) transitions in
the spinels AlVO and LiVO (under pressure). The high degeneracy
of CO states is lifted by a coupling to the rhombohedral lattice deformations
which favors transition to a CO state with inequivalent V(1) and V(2) sites
forming Kagom\'e and trigonal planes respectively. We construct an extended
Hubbard type model including a deformation potential which is treated in
unrestricted Hartree Fock approximation and describes correctly the observed
first-order CO transition. We also discuss the influence of associated orbital
order. Furthermore we suggest that due to different band fillings AlVO
should remain metallic while LiVO under pressure should become a
semiconductor when charge disproportionation sets in
Quantum Shock Waves - the case for non-linear effects in dynamics of electronic liquids
Using the Calogero model as an example, we show that the transport in
interacting non-dissipative electronic systems is essentially non-linear.
Non-linear effects are due to the curvature of the electronic spectrum near the
Fermi energy. As is typical for non-linear systems, propagating wave packets
are unstable. At finite time shock wave singularities develop, the wave packet
collapses, and oscillatory features arise. They evolve into regularly
structured localized pulses carrying a fractionally quantized charge - {\it
soliton trains}. We briefly discuss perspectives of observation of Quantum
Shock Waves in edge states of Fractional Quantum Hall Effect and a direct
measurement of the fractional charge
Modified spline-based navigation: Guaranteed safety for obstacle avoidance
© 2017, Springer International Publishing AG. Successful interactive collaboration with a human demands mobile robots to have an advanced level of autonomy, which basic requirements include social interaction, real time path planning and navigation in dynamic environment. For mobile robot path planning, potential function based methods provide classical yet powerful solutions. They are characterized with reactive local obstacle avoidance and implementation simplicity, but suffer from navigation function local minima. In this paper we propose a modification of our original spline-based path planning algorithm, which consists of two levels of planning. At the first level, Voronoi-based approach provides a number sub-optimal paths in different homotopic groups. At the second, these paths are optimized in an iterative manner with regard to selected criteria weights. A new safety criterion is integrated into both levels of path planning to guarantee path safety, while further optimization of a safe path relatively to other criteria is secondary. The modified algorithm was implemented in Matlab environment and demonstrated significant advantages over the original algorithm
Substructure in the stellar halo near the Sun:I. Data-driven clustering in integrals-of-motion space
Aims: Develop a data-driven and statistically based method for finding such
clumps in Integrals of Motion space for nearby halo stars and evaluating their
significance robustly. Methods: We use data from Gaia EDR3 extended with radial
velocities from ground-based spectroscopic surveys to construct a sample of
halo stars within 2.5 kpc from the Sun. We apply a hierarchical clustering
method that uses the single linkage algorithm in a 3D space defined by the
commonly used integrals of motion energy , together with two components of
the angular momentum, and . To evaluate the statistical
significance of the clusters found, we compare the density within an
ellipsoidal region centered on the cluster to that of random sets with similar
global dynamical properties. We pick out the signal at the location of their
maximum statistical significance in the hierarchical tree. We estimate the
proximity of a star to the cluster center using the Mahalanobis distance. We
also apply the HDBSCAN clustering algorithm in velocity space. Results: Our
procedure identifies 67 highly significant clusters (), containing
12\% of the sources in our halo set, and in total 232 subgroups or individual
streams in velocity space. In total, 13.8\% of the stars in our data set can be
confidently associated to a significant cluster based on their Mahalanobis
distance. Inspection of our data set reveals a complex web of relationships
between the significant clusters, suggesting that they can be tentatively
grouped into at least 6 main structures, many of which can be associated to
previously identified halo substructures, and a number of independent
substructures. This preliminary conclusion is further explored in an
accompanying paper by Ruiz-Lara et al., where we also characterize the
substructures in terms of their stellar populations. Conclusions: We find...
(abridged version)Comment: 16 pages, 14 figures, 2 tables. Accepted for publication in A&A. This
is the first in a series of papers, the second (Ruiz-Lara et al.) can be
found in https://ui.adsabs.harvard.edu/abs/2022arXiv220102405R/abstract Code
of the clustering algorithm can be found in
https://github.com/SofieLovdal/IOM_clusterin
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