255 research outputs found
Highest coefficient of scalar products in SU(3)-invariant integrable models
We study SU(3)-invariant integrable models solvable by nested algebraic Bethe
ansatz. Scalar products of Bethe vectors in such models can be expressed in
terms of a bilinear combination of their highest coefficients. We obtain
various different representations for the highest coefficient in terms of sums
over partitions. We also obtain multiple integral representations for the
highest coefficient.Comment: 17 page
Sound velocity and absorption measurements under high pressure using picosecond ultrasonics in diamond anvil cell. Application to the stability study of AlPdMn
We report an innovative high pressure method combining the diamond anvil cell
device with the technique of picosecond ultrasonics. Such an approach allows to
accurately measure sound velocity and attenuation of solids and liquids under
pressure of tens of GPa, overcoming all the drawbacks of traditional
techniques. The power of this new experimental technique is demonstrated in
studies of lattice dynamics, stability domain and relaxation process in a
metallic sample, a perfect single-grain AlPdMn quasicrystal, and rare gas, neon
and argon. Application to the study of defect-induced lattice stability in
AlPdMn up to 30 GPa is proposed. The present work has potential for application
in areas ranging from fundamental problems in physics of solid and liquid
state, which in turn could be beneficial for various other scientific fields as
Earth and planetary science or material research
Central extension of the reflection equations and an analog of Miki's formula
Two different types of centrally extended quantum reflection algebras are
introduced. Realizations in terms of the elements of the central extension of
the Yang-Baxter algebra are exhibited. A coaction map is identified. For the
special case of , a realization in terms of elements
satisfying the Zamolodchikov-Faddeev algebra - a `boundary' analog of Miki's
formula - is also proposed, providing a free field realization of
(q-Onsager) currents.Comment: 11 pages; two references added; to appear in J. Phys.
On Form Factors in nested Bethe Ansatz systems
We investigate form factors of local operators in the multi-component Quantum
Non-linear Schr\"odinger model, a prototype theory solvable by the so-called
nested Bethe Ansatz. We determine the analytic properties of the infinite
volume form factors using the coordinate Bethe Ansatz solution and we establish
a connection with the finite volume matrix elements. In the two-component
models we derive a set of recursion relations for the "magnonic form factors",
which are the matrix elements on the nested Bethe Ansatz states. In certain
simple cases (involving states with only one spin-impurity) we obtain explicit
solutions for the recursion relations.Comment: 34 pages, v2 (minor modifications
Direct Observation of Propagating Gigahertz Coherent Guided Acoustic Phonons in Free Standing Single Copper Nanowires
We report on gigahertz acoustic phonon waveguiding in free-standing single
copper nanowires studied by femtosecond transient reflectivity measurements.
The results are discussed on the basis of the semianalytical resolution of the
Pochhammer and Chree equation. The spreading of the generated Gaussian wave
packet of two different modes is derived analytically and compared with the
observed oscillations of the sample reflectivity. These experiments provide a
unique way to independently obtain geometrical and material characterization.
This direct observation of coherent guided acoustic phonons in a single
nano-object is also the first step toward nanolateral size acoustic transducer
and comprehensive studies of the thermal properties of nanowires
Generalized q-Onsager Algebras and Dynamical K-matrices
A procedure to construct -matrices from the generalized -Onsager
algebra \cO_{q}(\hat{g}) is proposed. This procedure extends the intertwiner
techniques used to obtain scalar (c-number) solutions of the reflection
equation to dynamical (non-c-number) solutions. It shows the relation between
soliton non-preserving reflection equations or twisted reflection equations and
the generalized -Onsager algebras. These dynamical -matrices are
important to quantum integrable models with extra degrees of freedom located at
the boundaries: for instance, in the quantum affine Toda field theories on the
half-line they yield the boundary amplitudes. As examples, the cases of
\cO_{q}(a^{(2)}_{2}) and \cO_{q}(a^{(1)}_{2}) are treated in details
Nested Bethe ansatz for `all' open spin chains with diagonal boundary conditions
We present in an unified and detailed way the nested Bethe ansatz for open
spin chains based on Y(gl(\fn)), Y(gl(\fm|\fn)), U_{q}(gl(\fn)) or
U_{q}(gl(\fm|\fn)) (super)algebras, with arbitrary representations (i.e.
`spins') on each site of the chain and diagonal boundary matrices
(K^+(u),K^-(u)). The nested Bethe anstaz applies for a general K^-(u), but a
particular form of the K^+(u) matrix.
The construction extends and unifies the results already obtained for open
spin chains based on fundamental representation and for some particular
super-spin chains. We give the eigenvalues, Bethe equations and the form of the
Bethe vectors for the corresponding models. The Bethe vectors are expressed
using a trace formula.Comment: 40 pages; examples of Bethe vectors added; Bethe equations for
U_q(gl(2/2)) added; misprints correcte
Absence of a Fermi surface in classical minimal four-dimensional gauged supergravity
We demonstrate that the two point function of the supercurrent dual to the
gravitino in the four-dimensional extremal anti-de Sitter Reissner-Nordstrom
black hole does not exhibit a Fermi surface singularity. In our analysis, we
utilize the ingoing Eddington-Finkelstein coordinate system, which enables us
to bypass certain complications in the determination of the allowed near
horizon behavior of the gravitino field at zero frequency. We check that our
method agrees with previous results for the massless charged Dirac field.Comment: 12 pages, 1 figur
Recommended from our members
Eltanin reports : cruises 37-39, 1969; 42-46, 1970 : hydrographic stations, bottom photographs, current measurements, nephelometer profiles
New reflection matrices for the U_q(gl(m|n)) case
We examine super symmetric representations of the B-type Hecke algebra. We
exploit such representations to obtain new non-diagonal solutions of the
reflection equation associated to the super algebra U_q(gl(m|n)). The boundary
super algebra is briefly discussed and it is shown to be central to the super
symmetric realization of the B-type Hecke algebraComment: 13 pages, Latex. A few alterations regarding the representations. A
reference adde
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