10,320 research outputs found
Finite N Index and Angular Momentum Bound from Gravity
We exactly compute the finite N index and BPS partition functions for N=4 SYM
theory in a newly proposed maximal angular momentum limit. The new limit is not
predicted from the superconformal algebra, but naturally arises from the
supergravity dual. We show that the index does not receive any finite N
corrections while the free BPS partition function does.Comment: 14 pages, v2: minor revisions, published versio
Functional characteristics of the calcium modulated proteins seen from an evolutionary perspective
We have constructed dendrograms relating 173 EF-hand proteins of known amino acid sequence. We aligned all of these proteins by their EF-hand domains, omitting interdomain regions. Initial dendrograms were computed by minimum mutation distance methods. Using these as starting points, we determined the best dendrogram by the method of maximum parsimony, scored by minimum mutation distance. We identified 14 distinct subfamilies as well as 6 unique proteins that are perhaps the sole representatives of other subfamilies. This information is given in tabular form. Within subfamilies one can easily align interdomain regions. The resulting dendrograms are very similar to those computed using domains only. Dendrograms constructed using pairs of domains show general congruence. However, there are enough exceptions to caution against an overly simple scheme in which one pair of gene duplications leads from one domain precurser to a four domain prototype from which all other forms evolved. The ability to bind calcium was lost and acquired several times during evolution. The distribution of introns does not conform to the dendrogram based on amino acid sequences. The rates of evolution appear to be much slower within subfamilies, especially within calmodulin, than those prior to the definition of subfamily
Holographic storage of multiple coherence gratings in a Bose-Einstein condensate
We demonstrate superradiant conversion between a two-mode collective atomic
state and a single-mode light field in an elongated cloud of Bose-condensed
atoms. Two off-resonant write beams induce superradiant Raman scattering,
producing two independent coherence gratings with a different wave vector in
the cloud. By applying phase-matched read beams after a controllable delay, the
gratings can be selectively converted into the light field also in a
superradiant way. Due to the large cooperativity parameter and the small
velocity width of the condensate, a high conversion efficiency of % and
a long storage time of s were achieved.Comment: 5 pages, 4 figure
Algebraic varieties with automorphism groups of maximal rank
We confirm, to some extent, the belief that a projective variety X has the
largest number (relative to the dimension of X) of independent commuting
automorphisms of positive entropy only when X is birational to a complex torus
or a quotient of a torus. We also include an addendum to an early paper though
it is not used in the present paper.Comment: Mathematische Annalen (to appear
On the Universal Tachyon and Geometrical Tachyon
We study properties of non-BPS D(p+1)-brane in the background of k
NS5-branes, with one transverse direction compactified on a circle, from the
point of view of Dirac-Born-Infeld action. We present the analysis of two
different embedding of non-BPS D(p+1)-brane in given background and study the
classical solutions of given world-volume theory. We argue for the
configuration of a non-BPS D(p+1)-brane which allows us to find solutions of
the equations of motion that give unified descriptions of G and U-type branes.Comment: 24 pages, minor change
PCAC and the Deficit of Forward Muons in pi^+ Production by Neutrinos
The K2K experiment, using a fine-grained detector in a neutrino beam of
energy has observed two-track events that can be
interpreted as a coherent reaction or an incoherent process , the final nucleon being unobserved. The data show a significant
deficit of forward-going muons in the interval ,
where a sizeable coherent signal is expected. We attempt an explanantion of
this effect, using a PCAC formula that includes the effect of the non-vanishing
muon mass. A suppression of about 25 % is caused by a destructive interference
of the axial vector and pseudoscalar (pion-exchange) amplitudes. The incoherent
background is also reduced by 10 - 15 %. As a consequence the discrepancy
between theory and observation is significantly reduced.Comment: 4 pages including 1 figure, changes in abstract and text; version to
appear in Phys.Lett.
Observables and Correlators in Nonrelativistic ABJM Theory
Non-relativistic ABJM theory is defined by Galilean limit of mass-deformed
N=6 Chern-Simons theory. Holographic string theory dual to the theory is not
known yet. To understand features candidate gravity dual might exhibit, we
examine local and nonlocal physical observables and their correlations in the
non-relativistic ABJM theory. We show that gauge invariant local observables
correspond to zero-norm states and that correlation functions among them are
trivial. We also show that a particular class of nonlocal observables, Wilson
loops, are topological in the sense that their correlation functions coincide
with those of pure Chern-Simons theory. We argue that the theory is
nevertheless physical and illustrate several physical observables whose
correlation functions are nontrivial. We also study quantum aspects. We show
that Chern-Simons level is finitely renormalized and that dilatation operator
acting on spin chain is trivial at planar limit. These results all point to
string scale geometry of gravity dual and to intriguing topological and
tensionless nature of dual string defined on it.Comment: 1+30 pages, no figure, v2. typos fixed and references adde
Degenerate dispersive equations arising in the study of magma dynamics
An outstanding problem in Earth science is understanding the method of
transport of magma in the Earth's mantle. Models for this process, transport in
a viscously deformable porous media, give rise to scalar degenerate,
dispersive, nonlinear wave equations. We establish a general local
well-posedness for a physical class of data (roughly ) via fixed point
methods. The strategy requires positive lower bounds on the solution. This is
extended to global existence for a subset of possible nonlinearities by making
use of certain conservation laws associated with the equations. Furthermore, we
construct a Lyapunov energy functional, which is locally convex about the
uniform state, and prove (global in time) nonlinear dynamic stability of the
uniform state for any choice of nonlinearity. We compare the dynamics to that
of other problems and discuss open questions concerning a larger range of
nonlinearities, for which we conjecture global existence.Comment: 27 Pages, 7 figures are not present in this version. See
http://www.columbia.edu/~grs2103/ for a PDF with figures. Submitted to
Nonlinearit
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