57,314 research outputs found

### On correlation functions of integrable models associated to the six-vertex R-matrix

We derive an analog of the master equation obtained recently for correlation
functions of the XXZ chain for a wide class of quantum integrable systems
described by the R-matrix of the six-vertex model, including in particular
continuum models. This generalized master equation allows us to obtain multiple
integral representations for the correlation functions of these models. We
apply this method to derive the density-density correlation functions of the
quantum non-linear Schrodinger model.Comment: 21 page

### Point interactions in one dimension and holonomic quantum fields

We introduce and study a family of quantum fields, associated to
delta-interactions in one dimension. These fields are analogous to holonomic
quantum fields of M. Sato, T. Miwa and M. Jimbo. Corresponding field operators
belong to an infinite-dimensional representation of the group SL(2,\Rb) in
the Fock space of ordinary harmonic oscillator. We compute form factors of such
fields and their correlation functions, which are related to the determinants
of Schroedinger operators with a finite number of point interactions. It is
also shown that these determinants coincide with tau functions, obtained
through the trivialization of the $\mathrm{det}^*$-bundle over a Grassmannian
associated to a family of Schroedinger operators.Comment: 17 page

### On the Magnetic Excitation Spectra of High Tc Cu Oxides up to the Energies far above the Resonance Energy

Magnetic excitation spectra c"(q,w) of YBa2Cu3Oy and La214 systems have been
studied. For La1.88Sr0.12CuO4, c"(q,w) have been measured up to ~30 meV and
existing data have been analyzed up to the energy w~150 meV by using the
phenomenological expression of the generalized magnetic susceptibility
c(q,w)=c0(q,w)/{1+J(q)c0(q,w)}, where c0(q,w) is the susceptibility of the
electrons without the exchange coupling J(q) among them. In the relatively low
energy region up to slightly above the resonance energy Er, it has been
reported by the authors' group that the expression can explain characteristics
of the q- and w-dependence of the spectra of YBa2Cu3Oy (YBCO or YBCOy). Here,
it is also pointed out that the expression can reproduce the rotation of four
incommensurate peaks of c"(q,w) within the a*-b* plane about (p/a, p/a) {or
so-called (p, p)} point by 45 degree, which occurs as w goes to the energy
region far above Er from E below Er. For La2-xSrxCuO4 and La2-xBaxCuO4,
agreements between the observed results and the calculations are less
satisfactory than for YBCO, indicating that we have to take account of the
existence of the "stripes" to consistently explain the observed c"(q,w) of
La214 system especially near x=1/8.Comment: 14 pages, 5 figure

### Driven localized excitations in the acoustic spectrum of small nonlinear macroscopic and microscopic lattices

Both bright and dark traveling, locked, intrinsic localized modes (ILMs) have
been generated with a spatially uniform driver at a frequency in the acoustic
spectrum of a nonlinear micromechanical cantilever array. Complementary
numerical simulations show that a minimum density of modes, hence array size,
is required for the formation of such locked smoothly running excitations.
Additional simulations on a small 1-D antiferromagnetic spin system are used to
illustrate that such uniformly driven running ILMs should be a generic feature
of a nanoscale atomic lattice.Comment: Physical Review Letters, accepte

### The Multicomponent KP Hierarchy: Differential Fay Identities and Lax Equations

In this article, we show that four sets of differential Fay identities of an
$N$-component KP hierarchy derived from the bilinear relation satisfied by the
tau function of the hierarchy are sufficient to derive the auxiliary linear
equations for the wave functions. From this, we derive the Lax representation
for the $N$-component KP hierarchy, which are equations satisfied by some
pseudodifferential operators with matrix coefficients. Besides the Lax
equations with respect to the time variables proposed in \cite{2}, we also
obtain a set of equations relating different charge sectors, which can be
considered as a generalization of the modified KP hierarchy proposed in
\cite{3}.Comment: 19 page

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