8,809 research outputs found
Quantizing Open Spin Chains with Variable Length: an example from Giant Gravitons
We study an XXX open spin chain with variable number of sites, where the
variability is introduced only at the boundaries. This model arises naturally
in the study of Giant Gravitons in the AdS/CFT correspondence. We show how to
quantize the spin chain by mapping its states to a bosonic lattice of finite
length with sources and sinks of particles at the boundaries. Using coherent
states, we show how the Hamiltonian for the bosonic lattice gives the correct
description of semiclassical open strings ending on Giant Gravitons.Comment: 4 pages. v2: updated reference
Particle-vortex dynamics in noncommutative space
We study the problem of a charged particle in the presence of a uniform
magnetic field plus a vortex in noncommutative planar space considering the two
possible non-commutative extensions of the corresponding Hamiltonian, namely
the ``fundamental'' and the ``antifundamental'' representations. Using a Fock
space formalism we construct eigenfunctions and eigenvalues finding in each
case half of the states existing in the ordinary space case. In the limit of
we recover the two classes of states found in ordinary space,
relevant for the study of anyon physics.Comment: 13 pages, no figures, plain LaTeX. References adde
Breakdown of the Fermi-liquid regime in the 2D Hubbard model from a two-loop field-theoretical renormalization group approach
We analyze the particle-hole symmetric two-dimensional Hubbard model on a
square lattice starting from weak-to-moderate couplings by means of the
field-theoretical renormalization group (RG) approach up to two-loop order.
This method is essential in order to evaluate the effect of the
momentum-resolved anomalous dimension which arises in the
normal phase of this model on the corresponding low-energy single-particle
excitations. As a result, we find important indications pointing to the
existence of a non-Fermi liquid (NFL) regime at temperature displaying
a truncated Fermi surface (FS) for a doping range exactly in between the
well-known antiferromagnetic insulating and the -wave singlet
superconducting phases. This NFL evolves as a function of doping into a
correlated metal with a large FS before the -wave pairing
susceptibility finally produces the dominant instability in the low-energy
limit.Comment: 9 pages, 9 figures; published in Phys. Rev.
Ladders for Wilson Loops Beyond Leading Order
We set up a general scheme to resum ladder diagrams for the quark-anti-quark
potential in N=4 super-Yang-Mills theory, and do explicit calculations at the
next-to-leading order. The results perfectly agree with string theory in
AdS(5)xS(5) when continued to strong coupling, in spite of a potential
order-of-limits problem.Comment: 18 pages, 5 figure
Spectral singularities in PT-symmetric periodic finite-gap systems
The origin of spectral singularities in finite-gap singly periodic
PT-symmetric quantum systems is investigated. We show that they emerge from a
limit of band-edge states in a doubly periodic finite gap system when the
imaginary period tends to infinity. In this limit, the energy gaps are
contracted and disappear, every pair of band states of the same periodicity at
the edges of a gap coalesces and transforms into a singlet state in the
continuum. As a result, these spectral singularities turn out to be analogous
to those in the non-periodic systems, where they appear as zero-width
resonances. Under the change of topology from a non-compact into a compact one,
spectral singularities in the class of periodic systems we study are
transformed into exceptional points. The specific degeneration related to the
presence of finite number of spectral singularities and exceptional points is
shown to be coherently reflected by a hidden, bosonized nonlinear
supersymmetry.Comment: 16 pages, 3 figures; a difference between spectral singularities and
exceptional points specified, the version to appear in PR
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