37,502 research outputs found
Classical Extended Conformal Algebras Associated with Constrained KP Hierarchy
We examine the conformal property of the second Hamiltonian structure of
constrained KP hierarchy derived by Oevel and Strampp. We find that it
naturallygives a family of nonlocal extended conformal algebras. We give two
examples of such algebras and find that they are similar to Bilal's V algebra.
By taking a gauge transformation one can map the constrained KP hierarchy to
Kuperschmidt's nonstandard Lax hierarchy. We consider the second Hamiltonian
structure in this representation. We show that after mapping the Lax operator
to a pure differential operator the second structure becomes the sum of the
second and the third Gelfand-Dickey brackets defined by this differential
operator. We show that this Hamiltonian structure defines the W-U(1)-Kac-Moody
algebra by working out its conformally covariant form.Comment: NHCU-HEP-94-28, 19 pages (Plain TeX
Gelfand-Dikii Brackets for Nonstandard Lax Equations
We generalize the construction of Gelfand-Dikii brackets to the case of
nonstandard Lax equations. We also discuss the possible origin of Kac-Moody
algebras present in such systems.Comment: 11 pages, Preprint no. UR1347, ER40685-79
Continuous topological phase transitions between clean quantum Hall states
Continuous transitions between states with the {\em same} symmetry but
different topological orders are studied. Clean quantum Hall (QH) liquids with
neutral quasiparticles are shown to have such transitions. For clean bilayer
(nnm) states, a continous transition to other QH states (including non-Abelian
states) can be driven by increasing interlayer repulsion/tunneling. The
effective theories describing the critical points at some transitions are
derived.Comment: 4 pages, RevTeX, 2 eps figure
Non-Universality of Transverse Momentum Dependent Parton Distributions at Small-x
We study the universality issue of the transverse momentum dependent parton
distributions at small-x, by comparing the initial/final state interaction
effects in dijet-correlation in pA collisions with those in deep inelastic
lepton nucleus scattering. We demonstrate the non-universality by performing an
explicit calculation in a particular model where the multiple gauge boson
exchange contributions are summed up to all orders. We comment on the
implications of our results on the theoretical interpretation of di-hadron
correlation in dA collisions in terms of the saturation phenomena in deep
inelastic lepton nucleus scattering.Comment: 11 pages, 3 figure
Binding Transition in Quantum Hall Edge States
We study a class of Abelian quantum Hall (QH) states which are topologically
unstable (T-unstable). We find that the T-unstable QH states can have a phase
transition on the edge which causes a binding between electrons and reduces the
number of gapless edge branches. After the binding transition, the
single-electron tunneling into the edge gains a finite energy gap, and only
certain multi-electron co-tunneling (such as three-electron co-tunneling for
edges) can be gapless. Similar phenomenon also appear for edge state
on the boundary between certain QH states. For example edge on the boundary
between and states only allow three-electron co-tunneling at
low energies after the binding transition.Comment: 4 pages, RevTeX, 1 figur
Tree-Level Amplitudes in N=8 Supergravity
We present an algorithm for writing down explicit formulas for all tree
amplitudes in N=8 supergravity, obtained from solving the supersymmetric
on-shell recursion relations. The formula is patterned after one recently
obtained for all tree amplitudes in N=4 super Yang-Mills which involves nested
sums of dual superconformal invariants. We find that all graviton amplitudes
can be written in terms of exactly the same structure of nested sums with two
modifications: the dual superconformal invariants are promoted from N=4 to N=8
superspace in the simplest manner possible--by squaring them--and certain
additional non-dual conformal gravity dressing factors (independent of the
superspace coordinates) are inserted into the nested sums. To illustrate the
procedure we give explicit closed-form formulas for all NMHV, NNMHV and NNNMV
gravity superamplitudes.Comment: 27 pages, 5 figures, v2: typos correcte
High-Efficient Parallel CAVLC Encoders on Heterogeneous Multicore Architectures
This article presents two high-efficient parallel realizations of the context-based adaptive variable length coding (CAVLC) based on heterogeneous multicore processors. By optimizing the architecture of the CAVLC encoder, three kinds of dependences are eliminated or weaken, including the context-based data dependence, the memory accessing dependence and the control dependence. The CAVLC pipeline is divided into three stages: two scans, coding, and lag packing, and be implemented on two typical heterogeneous multicore architectures. One is a block-based SIMD parallel CAVLC encoder on multicore stream processor STORM. The other is a component-oriented SIMT parallel encoder on massively parallel architecture GPU. Both of them exploited rich data-level parallelism. Experiments results show that compared with the CPU version, more than 70 times of speedup can be obtained for STORM and over 50 times for GPU. The implementation of encoder on STORM can make a real-time processing for 1080p @30fps and GPU-based version can satisfy the requirements for 720p real-time encoding. The throughput of the presented CAVLC encoders is more than 10 times higher than that of published software encoders on DSP and multicore platforms
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