264 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
An eco-geomorphic model of tidal channel initiation and elaboration in progressive marsh accretional contexts
The formation and evolution of tidal networks have been described through various theories
which mostly assume that tidal network development results from erosional processes, therefore
emphasizing the chief role of external forcing triggering channel net erosion such as tidal currents. In
contrast, in the present contribution we explore the influence of sediment supply in governing tidal channel
initiation and further elaboration using an ecogeomorphic modeling framework. This deliberate choice of
environmental conditions allows for the investigation of tidal network growth and development in different
sedimentary contexts and provides evidences for the occurrence of both erosional and depositional
channel-forming processes. Results show that these two mechanisms in reality coexist but act at different
time scales: channel initiation stems from erosional processes, while channel elaboration mostly results
from depositional processes. Furthermore, analyses suggest that tidal network ontogeny is accelerated as
the marsh accretional activity increases, revealing the high magnitude and prevalence of the depositional
processes in governing the morphodynamic evolution of the tidal network. On a second stage, we analyze
the role of different initial topographic configurations in driving the development of tidal networks. Results
point out an increase in network complexity over highly perturbed initial topographic surfaces, highlighting
the legacy of initial conditions on channel morphological properties. Lastly, the consideration that
landscape evolution depends significantly on the parameterization of the vegetation biomass distribution
suggests that the claim to use uncalibrated models for vegetation dynamics is still questionable when
studying real cases
Évolution à long terme du peuplement piscicole du bassin de la Seine
Des données anciennes issues de la littérature sont utilisées pour apprécier les conséquences des activités humaines sur l'évolution de la structure des communautés piscicoles du bassin de la Seine
On factorizing -matrices in and spin chains
We consider quantum spin chains arising from -fold tensor products of the
fundamental evaluation representations of and .
Using the partial -matrix formalism from the seminal work of Maillet and
Sanchez de Santos, we derive a completely factorized expression for the
-matrix of such models and prove its equivalence to the expression obtained
by Albert, Boos, Flume and Ruhlig. A new relation between the -matrices and
the Bethe eigenvectors of these spin chains is given.Comment: 30 page
Quantifying the physical alterations of river reaches using a regional river morphology reference model. A step towards river restoration.
River engineeringRiver habitat management and restoratio
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
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.
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
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
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