134,774 research outputs found
Ultra High Energy Cosmic Rays: Strangelets? -- Extra dimensions, TeV-scale black holes and strange matter
The conjecture that ultra high energy cosmic rays (UHECRs) are actually
strangelets is discussed. Besides the reason that strangelets can do as cosmic
rays beyond the GZK-cutoff, another argument to support the conjecture is
addressed in this letter via the study of formation of TeV-scale microscopic
black holes when UHECRs bombarding bare strange stars. It is proposed that the
exotic quark surface of a bare strange star could be an effective
astro-laboratory in the investigations of the extra dimensions and of the
detection of ultra-high energy neutrino fluxes. The flux of neutrinos (and
other point-like particles) with energy >2.3 x 10^{20} eV could be expected to
be smaller than 10^{-26} cm^{-2}$ s^{-1} if there are two extra spatial
dimensions.Comment: accepted by Chin. Phys. Lett., or at
http://vega.bac.pku.edu.cn/~rxxu/publications/index_P.ht
Internal Energy of the Potts model on the Triangular Lattice with Two- and Three-body Interactions
We calculate the internal energy of the Potts model on the triangular lattice
with two- and three-body interactions at the transition point satisfying
certain conditions for coupling constants. The method is a duality
transformation. Therefore we have to make assumptions on uniqueness of the
transition point and that the transition is of second order. These assumptions
have been verified to hold by numerical simulations for q=2, 3 and 4, and our
results for the internal energy are expected to be exact in these cases.Comment: 9 pages, 4 figure
On the duality relation for correlation functions of the Potts model
We prove a recent conjecture on the duality relation for correlation
functions of the Potts model for boundary spins of a planar lattice.
Specifically, we deduce the explicit expression for the duality of the n-site
correlation functions, and establish sum rule identities in the form of the
M\"obius inversion of a partially ordered set. The strategy of the proof is by
first formulating the problem for the more general chiral Potts model. The
extension of our consideration to the many-component Potts models is also
given.Comment: 17 pages in RevTex, 5 figures, submitted to J. Phys.
New critical frontiers for the Potts and percolation models
We obtain the critical threshold for a host of Potts and percolation models
on lattices having a structure which permits a duality consideration. The
consideration generalizes the recently obtained thresholds of Scullard and Ziff
for bond and site percolation on the martini and related lattices to the Potts
model and to other lattices.Comment: 9 pages, 5 figure
On the Throughput of Channels that Wear Out
This work investigates the fundamental limits of communication over a noisy
discrete memoryless channel that wears out, in the sense of signal-dependent
catastrophic failure. In particular, we consider a channel that starts as a
memoryless binary-input channel and when the number of transmitted ones causes
a sufficient amount of damage, the channel ceases to convey signals. Constant
composition codes are adopted to obtain an achievability bound and the
left-concave right-convex inequality is then refined to obtain a converse bound
on the log-volume throughput for channels that wear out. Since infinite
blocklength codes will always wear out the channel for any finite threshold of
failure and therefore cannot convey information at positive rates, we analyze
the performance of finite blocklength codes to determine the maximum expected
transmission volume at a given level of average error probability. We show that
this maximization problem has a recursive form and can be solved by dynamic
programming. Numerical results demonstrate that a sequence of block codes is
preferred to a single block code for streaming sources.Comment: 23 pages, 1 table, 11 figures, submitted to IEEE Transactions on
Communication
Holographic Dark Energy Characterized by the Total Comoving Horizon and Insights to Cosmological Constant and Coincidence Problem
The observed acceleration of the present universe is shown to be well
explained by the holographic dark energy characterized by the total comoving
horizon of the universe (HDE). It is of interest to notice that the very
large primordial part of the comoving horizon generated by the inflation of
early universe makes the HDE behave like a cosmological constant. As a
consequence, both the fine-tuning problem and the coincidence problem can
reasonably be understood with the inflationary universe and holographical
principle. We present a systematic analysis and obtain a consistent
cosmological constraint on the HDE model based on the recent cosmological
observations. It is found that the HDE model gives the best-fit result
() and the minimal
which is compatible with for the CDM model.Comment: 17 pages, 4 figures, two eqs. (26)(27) added for the consistent
approximate solution of dark energy in early universe, references added,
published version in PR
Basis-conjugating automorphisms of a free group and associated Lie algebras
Let F_n = denote the free group with generators {x_1,...,x_n}.
Nielsen and Magnus described generators for the kernel of the canonical
epimorphism from the automorphism group of F_n to the general linear group over
the integers. In particular among them are the automorphisms chi_{k,i} which
conjugate the generator x_k by the generator x_i leaving the x_j fixed for j
not k. A computation of the cohomology ring as well as the Lie algebra obtained
from the descending central series of the group generated by chi_{k,i} for i<k
is given here. Partial results are obtained for the group generated by all
chi_{k,i}.Comment: This is the version published by Geometry & Topology Monographs on 22
February 200
- …