495 research outputs found
Computational codon optimization of synthetic gene for protein expression
10.1186/1752-0509-6-134BMC Systems Biology6
3-D Perturbations in Conformal Turbulence
The effects of three-dimensional perturbations in two-dimensional turbulence
are investigated, through a conformal field theory approach. We compute scaling
exponents for the energy spectra of enstrophy and energy cascades, in a strong
coupling limit, and compare them to the values found in recent experiments. The
extension of unperturbed conformal turbulence to the present situation is
performed by means of a simple physical picture in which the existence of small
scale random forces is closely related to deviations of the exact
two-dimensional fluid motion.Comment: Discussion of intermittency improved. Figure include
Chern-Simons Vortices in Supergravity
We study supersymmetric vortex solutions in three-dimensional abelian gauged
supergravity. First, we construct the general U(1)-gauged D=3, N=2 supergravity
whose scalar sector is an arbitrary Kahler manifold with U(1) isometry. This
construction clarifies the connection between local supersymmetry and the
specific forms of some scalar potentials previously found in the literature --
in particular, it provides the locally supersymmetric embedding of the abelian
Chern-Simons Higgs model. We show that the Killing spinor equations admit
rotationally symmetric vortex solutions with asymptotically conical geometry
which preserve half of the supersymmetry.Comment: 26 pages, LaTeX2
The road to deterministic matrices with the restricted isometry property
The restricted isometry property (RIP) is a well-known matrix condition that
provides state-of-the-art reconstruction guarantees for compressed sensing.
While random matrices are known to satisfy this property with high probability,
deterministic constructions have found less success. In this paper, we consider
various techniques for demonstrating RIP deterministically, some popular and
some novel, and we evaluate their performance. In evaluating some techniques,
we apply random matrix theory and inadvertently find a simple alternative proof
that certain random matrices are RIP. Later, we propose a particular class of
matrices as candidates for being RIP, namely, equiangular tight frames (ETFs).
Using the known correspondence between real ETFs and strongly regular graphs,
we investigate certain combinatorial implications of a real ETF being RIP.
Specifically, we give probabilistic intuition for a new bound on the clique
number of Paley graphs of prime order, and we conjecture that the corresponding
ETFs are RIP in a manner similar to random matrices.Comment: 24 page
Problems with Time-Varying Extra Dimensions or "Cardassian Expansion" as Alternatives to Dark Energy
It has recently been proposed that the Universe might be accelerating as a
consequence of extra dimensions with time varying size. We show that although
these scenarios can lead to acceleration, they run into serious difficulty when
taking into account limits on the time variation of the four dimensional
Newton's constant. On the other hand, models of ``Cardassian'' expansion based
on extra dimensions which have been constructed so far violate the weak energy
condition for the bulk stress energy, for parameters that give an accelerating
universe.Comment: 8 pages, minor changes. To appear in Physical Review
Complementarity of the CERN Large Hadron Collider and the International Linear Collider
The next-generation high-energy facilities, the CERN Large Hadron Collider
(LHC) and the prospective International Linear Collider (ILC), are
expected to unravel new structures of matter and forces from the electroweak
scale to the TeV scale. In this report we review the complementary role of LHC
and ILC in drawing a comprehensive and high-precision picture of the mechanism
breaking the electroweak symmetries and generating mass, and the unification of
forces in the frame of supersymmetry.Comment: 14 pages, 17 figures, to be published in "Supersymmetry on the Eve of
the LHC", a special volume of European Physical Journal C, Particles and
Fields (EPJC) in memory of Julius Wes
The Role of Color Neutrality in Nuclear Physics--Modifications of Nucleonic Wave Functions
The influence of the nuclear medium upon the internal structure of a
composite nucleon is examined. The interaction with the medium is assumed to
depend on the relative distances between the quarks in the nucleon consistent
with the notion of color neutrality, and to be proportional to the nucleon
density. In the resulting description the nucleon in matter is a superposition
of the ground state (free nucleon) and radial excitations. The effects of the
nuclear medium on the electromagnetic and weak nucleon form factors, and the
nucleon structure function are computed using a light-front constituent quark
model. Further experimental consequences are examined by considering the
electromagnetic nuclear response functions. The effects of color neutrality
supply small but significant corrections to predictions of observables.Comment: 37 pages, postscript figures available on request to
[email protected]
Proximity effect at superconducting Sn-Bi2Se3 interface
We have investigated the conductance spectra of Sn-Bi2Se3 interface junctions
down to 250 mK and in different magnetic fields. A number of conductance
anomalies were observed below the superconducting transition temperature of Sn,
including a small gap different from that of Sn, and a zero-bias conductance
peak growing up at lower temperatures. We discussed the possible origins of the
smaller gap and the zero-bias conductance peak. These phenomena support that a
proximity-effect-induced chiral superconducting phase is formed at the
interface between the superconducting Sn and the strong spin-orbit coupling
material Bi2Se3.Comment: 7 pages, 8 figure
The Renormalization Group with Exact beta-Functions
The perturbative -function is known exactly in a number of
supersymmetric theories and in the 't Hooft renormalization scheme in the
model. It is shown how this allows one to compute the effective
action exactly for certain background field configurations and to relate bare
and renormalized couplings. The relationship between the MS and SUSY
subtraction schemes in super Yang-Mills theory is discussed
Centrality Dependence of the High p_T Charged Hadron Suppression in Au+Au collisions at sqrt(s_NN) = 130 GeV
PHENIX has measured the centrality dependence of charged hadron p_T spectra
from central Au+Au collisions at sqrt(s_NN)=130 GeV. The truncated mean p_T
decreases with centrality for p_T > 2 GeV/c, indicating an apparent reduction
of the contribution from hard scattering to high p_T hadron production. For
central collisions the yield at high p_T is shown to be suppressed compared to
binary nucleon-nucleon collision scaling of p+p data. This suppression is
monotonically increasing with centrality, but most of the change occurs below
30% centrality, i.e. for collisions with less than about 140 participating
nucleons. The observed p_T and centrality dependence is consistent with the
particle production predicted by models including hard scattering and
subsequent energy loss of the scattered partons in the dense matter created in
the collisions.Comment: 7 pages text, LaTeX, 6 figures, 2 tables, 307 authors, resubmitted to
Phys. Lett. B. Revised to address referee concerns. Plain text data tables
for the points plotted in figures for this and previous PHENIX publications
are publicly available at
http://www.phenix.bnl.gov/phenix/WWW/run/phenix/papers.htm
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