1,380 research outputs found
Weighted Besov and Triebel--Lizorkin spaces associated to operators
Let be a space of homogeneous type and be a nonnegative self-adjoint
operator on satisfying Gaussian upper bounds on its heat kernels. In
this paper we develop the theory of weighted Besov spaces
and weighted Triebel--Lizorkin spaces
associated to the operator for the full
range , and being in the Muckenhoupt
weight class . Similarly to the classical case in the Euclidean
setting, we prove that our new spaces satisfy important features such as
continuous charaterizations in terms of square functions, atomic decompositions
and the identifications with some well known function spaces such as Hardy type
spaces and Sobolev type spaces. Moreover, with extra assumptions on the
operator , we prove that the new function spaces associated to coincide
with the classical function spaces. Finally we apply our results to prove the
boundedness of the fractional power of and the spectral multiplier of
in our new function spaces.Comment: 57 page
On multiplicative subgroups in division rings
Let be a division ring. In this paper, we investigate properties of
subgroups of an arbitrary subnormal subgroup of the multiplicative group
of . The new obtained results generalize some previous results on subgroups
of .Comment: 14 page
The existence of free non-cyclic subgroups in weakly locally finite division rings
In this paper we prove that every non-central subnormal subgroup of the
multiplicative group of a weakly locally finite division ring contains free
non-cyclic subgroups
On perfect order subsets in finite groups
If is a finite group and then the set of all elements of
having the same order as is called {\em an order subset of determined
by } (see [2]). We say that is a {\em group with perfect order subsets}
or briefly, is a {\em -group} if the number of elements in each order
subset of is a divisor of . In this paper we prove that for any , the symmetric group is not -group. This gives the positive
answer to one of two questions rising from Conjecture 5.2 in [3].Comment: 8 page
Protein escape at the ribosomal exit tunnel: Effects of native interactions, tunnel length and macromolecular crowding
How fast a post-translational nascent protein escapes from the ribosomal exit
tunnel is relevant to its folding and protection against aggregation. Here, by
using Langevin molecular dynamics, we show that non-local native interactions
help decreasing the escape time, and foldable proteins generally escape much
faster than same-length self-repulsive homopolymers at low temperatures. The
escape process, however, is slowed down by the local interactions that
stabilize the {\alpha}-helices. The escape time is found to increase with both
the tunnel length and the concentration of macromolecular crowders outside the
tunnel. We show that a simple diffusion model described by the Smoluchowski
equation with an effective linear potential can be used to map out the escape
time distribution for various tunnel lengths and various crowder
concentrations. The consistency between the simulation data and the diffusion
model however is found only for the tunnel length smaller than a cross-over
length of 90 {\AA} to 110 {\AA}, above which the escape time increases much
faster with the tunnel length. It is suggested that the length of ribosomal
exit tunnel has been selected by evolution to facilitate both the efficient
folding and efficient escape of single domain proteins. We show that
macromolecular crowders lead to an increase of the escape time, and attractive
crowders are unfavorable for the folding of nascent polypeptide
Weighted Hardy spaces associated to operators and boundedness of singular integrals
Let be a space of homogeneous type, i.e. the measure
satisfies doubling (volume) property with respect to the balls defined by the
metric . Let be a non-negative self-adjoint operator on . Assume
that the semigroup of satisfies the Davies-Gaffney estimates. In this
paper, we study the weighted Hardy spaces , ,
associated to the operator on the space . We establish the atomic and
the molecular characterizations of elements in . As applications,
we obtain the boundedness on \HL for the generalized Riesz transforms
associated to and for the spectral multipliers of .Comment: 26 pages, some minor errors were correcte
Hardy spaces, Regularized BMO spaces and the boundedness of Calder\'on-Zygmund operators on non-homogeneous spaces
One defines a non-homogeneous space as a metric space equipped
with a non-doubling measure so that the volume of the ball with center
, radius has an upper bound of the form for some . The aim
of this paper is to study the boundedness of a Calder\'on-Zygmund operator
as well as the boundedness of certain related singular integrals associated
with on various function spaces on such as the Hardy spaces, the
spaces and the regularized BMO spaces. This article thus extends the work
of X. Tolsa \cite{T1} on the non-homogeneous space to the
setting of a general non-homogeneous space . While our framework is
similar to that of \cite{H}, we are able to obtain quite a few properties
similar to those of Calder\'on-Zygmund operators on doubling spaces, including
the following for such an operator : weak type estimate, boundedness
from Hardy space into , boundedness from into the regularized
BMO and an interpolation theorem. We also prove that the dual space of the
Hardy space is the regularized BMO space, obtain a Calder\'on-Zygmund
decomposition on the non-homogeneous space and use this
decomposition to show the boundedness of the maximal operators in the form of
Cotlar inequality as well as the boundedness of commutators of
Calder\'on-Zygmund operators and BMO functions.Comment: 37 pages; some minor changes; to appear in Journal of Geometric
Analysi
Folding and escape of nascent proteins at ribosomal exit tunnel
We investigate the interplay between post-translational folding and escape of
two small single-domain proteins at the ribosomal exit tunnel by using Langevin
dynamics with coarse-grained models. It is shown that at temperatures lower or
near the temperature of the fastest folding, folding proceeds concomitantly
with the escape process, resulting in vectorial folding and enhancement of
foldability of nascent proteins. The concomitance between the two processes,
however, deteriorates as temperature increases. Our folding simulations as well
as free energy calculation by using umbrella sampling show that, at low
temperatures, folding at the tunnel follows one or two specific pathways
without kinetic traps. It is shown that the escape time can be mapped to a
one-dimensional diffusion model with two different regimes for temperatures
above and below the folding transition temperature. Attractive interactions
between amino acids and attractive sites on the tunnel wall lead to a free
energy barrier along the escape route of protein. It is suggested that this
barrier slows down the escape process and consequently promotes correct folding
of the released nascent protein.Comment: to appear in J. Chem. Phy
On subnormal subgroups in division rings containing a non-abelian solvable subgroup
Let be a division ring with center and a subnormal subgroup of
the multiplicative group of . Assume that contains a non-abelian
solvable subgroup. In this paper, we study the problem on the existence of
non-abelian free subgroups in . In particular, we show that if either is
algebraic over or is uncountable, then contains a non-abelian free
subgroup.Comment: 10 page
Regularity estimates for Green operators of Dirichlet and Neumann problems on weighted Hardy spaces
In this paper we first study the generalized weighted Hardy spaces
for associated to nonnegative self-adjoint operators
satisfying Gaussian upper bounds on the space of homogeneous type in
both cases of finite and infinite measure. We show that the weighted Hardy
spaces defined via maximal functions and atomic decompositions coincide. Then
we prove weighted regularity estimates for the Green operators of the
inhomogeneous Dirichlet and Neumann problems in suitable bounded or unbounded
domains including bounded semiconvex domains, convex regions above a Lipschitz
graph and upper half-spaces. Our estimates are in terms of weighted
spaces for the range and in terms of the new weighted Hardy spaces
for the range . Our regularity estimates for the Green operators
under the weak smoothness assumptions on the boundaries of the domains are new,
especially the estimates on Hardy spaces for the full range and the
case of unbounded domains.Comment: 26 page
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