8,065 research outputs found
On equivalence of equations solutions of gravity field and homogenous inertia field
The metric of a homogenously accelerated system found by Harry Lass is a
solution of the Einstein s equation. The metric of an isotropic homogenous
field must satisfy the new gravitational equation.Comment: 5 pages, 1 figur
Introduction to Khovanov Homologies. III. A new and simple tensor-algebra construction of Khovanov-Rozansky invariants
We continue to develop the tensor-algebra approach to knot polynomials with
the goal to present the story in elementary and comprehensible form. The
previously reviewed description of Khovanov cohomologies for the gauge group of
rank N-1=1 was based on the cut-and-join calculus of the planar cycles, which
are involved rather artificially. We substitute them by alternative and natural
set of cycles, not obligatory planar. Then the whole construction is
straightforwardly lifted from SL(2) to SL(N) and reproduces Khovanov-Rozansky
(KR) polynomials, simultaneously for all values of N. No matrix factorization
and related tedious calculations are needed in such approach, which can
therefore become not only conceptually, but also practically useful.Comment: 66 page
Ubiquitous nucleosome unwrapping in the yeast genome
Nucleosome core particle is a dynamic structure -- DNA may transiently peel
off the histone octamer surface due to thermal fluctuations or the action of
chromatin remodeling enzymes. Partial DNA unwrapping enables easier access of
DNA-binding factors to their target sites and thus may provide a dominant
pathway for effecting rapid and robust access to DNA packaged into chromatin.
Indeed, a recent high-resolution map of distances between neighboring
nucleosome dyads in \emph{S.cerevisiae} shows that at least 38.7\% of all
nucleosomes are partially unwrapped. The extent of unwrapping follows a
stereotypical pattern in the vicinity of genes, reminiscent of the canonical
pattern of nucleosome occupancy in which nucleosomes are depleted over
promoters and well-positioned over coding regions. To explain these
observations, we developed a biophysical model which employs a 10-11 base pair
periodic nucleosome energy profile. The profile, based on the pattern of
histone-DNA contacts in nucleosome crystal structures and the idea of linker
length discretization, accounts for both nucleosome unwrapping and higher-order
chromatin structure. Our model reproduces the observed genome-wide distribution
of inter-dyad distances, and accounts for patterns of nucleosome occupancy and
unwrapping around coding regions. At the same time, our approach explains
\emph{in vitro} measurements of accessibility of nucleosome-covered binding
sites, and of nucleosome-induced cooperativity between DNA-binding factors. We
are able to rule out several alternative scenarios of nucleosome unwrapping as
inconsistent with the genomic data.Comment: 49 pages; 15 figure
Entropy production in open quantum systems: exactly solvable qubit models
We present analytical results for the time-dependent information entropy in
exactly solvable two-state (qubit) models. The first model describes dephasing
(decoherence) in a qubit coupled to a bath of harmonic oscillators. The entropy
production for this model in the regimes of "complete" and "incomplete"
decoherence is discussed. As another example, we consider the damped
Jaynes-Cummings model describing a spontaneous decay of a two-level system into
the field vacuum. It is shown that, for all strengths of coupling, the open
system passes through the mixed state with the maximum information entropy.Comment: 9 pages, 3 figure
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