132 research outputs found
Bethe roots and refined enumeration of alternating-sign matrices
The properties of the most probable ground state candidate for the XXZ spin
chain with the anisotropy parameter equal to -1/2 and an odd number of sites is
considered. Some linear combinations of the components of the considered state,
divided by the maximal component, coincide with the elementary symmetric
polynomials in the corresponding Bethe roots. It is proved that those
polynomials are equal to the numbers providing the refined enumeration of the
alternating-sign matrices of order M+1 divided by the total number of the
alternating-sign matrices of order M, for the chain of length 2M+1.Comment: LaTeX 2e, 12 pages, minor corrections, references adde
Direct SIMS Determination of the InxGa1-xN Mole Fraction
We demonstrate that our secondary mass ion spectroscopy (SIMS) method for the determination of the mole fraction in solid InxGa1-xN solutions is accurate and reproduceable without need of reference samples. The method is based on measuring relative current values of CsM+ (M=Ga, In) secondary ions. The claim of reliable SIMS determination without reference samples was confirmed by four independent analytical methods on the same samples with a relative error in the InN mole fraction determination below 15
Exact expressions for correlations in the ground state of the dense O(1) loop model
Conjectures for analytical expressions for correlations in the dense O
loop model on semi infinite square lattices are given. We have obtained these
results for four types of boundary conditions. Periodic and reflecting boundary
conditions have been considered before. We give many new conjectures for these
two cases and review some of the existing results. We also consider boundaries
on which loops can end. We call such boundaries ''open''. We have obtained
expressions for correlations when both boundaries are open, and one is open and
the other one is reflecting. Also, we formulate a conjecture relating the
ground state of the model with open boundaries to Fully Packed Loop models on a
finite square grid. We also review earlier obtained results about this relation
for the three other types of boundary conditions. Finally, we construct a
mapping between the ground state of the dense O loop model and the XXZ
spin chain for the different types of boundary conditions.Comment: 25 pages, version accepted by JSTA
Refined Razumov-Stroganov conjectures for open boundaries
Recently it has been conjectured that the ground-state of a Markovian
Hamiltonian, with one boundary operator, acting in a link pattern space is
related to vertically and horizontally symmetric alternating-sign matrices
(equivalently fully-packed loop configurations (FPL) on a grid with special
boundaries).We extend this conjecture by introducing an arbitrary boundary
parameter. We show that the parameter dependent ground state is related to
refined vertically symmetric alternating-sign matrices i.e. with prescribed
configurations (respectively, prescribed FPL configurations) in the next to
central row.
We also conjecture a relation between the ground-state of a Markovian
Hamiltonian with two boundary operators and arbitrary coefficients and some
doubly refined (dependence on two parameters) FPL configurations. Our
conjectures might be useful in the study of ground-states of the O(1) and XXZ
models, as well as the stationary states of Raise and Peel models.Comment: 11 pages LaTeX, 8 postscript figure
On FPL configurations with four sets of nested arches
The problem of counting the number of Fully Packed Loop (FPL) configurations
with four sets of a,b,c,d nested arches is addressed. It is shown that it may
be expressed as the problem of enumeration of tilings of a domain of the
triangular lattice with a conic singularity. After reexpression in terms of
non-intersecting lines, the Lindstr\"om-Gessel-Viennot theorem leads to a
formula as a sum of determinants. This is made quite explicit when
min(a,b,c,d)=1 or 2. We also find a compact determinant formula which generates
the numbers of configurations with b=d.Comment: 22 pages, TeX, 16 figures; a new formula for a generating function
adde
Non-local space-time supersymmetry on the lattice
We show that several well-known one-dimensional quantum systems possess a
hidden nonlocal supersymmetry. The simplest example is the open XXZ spin chain
with \Delta=-1/2. We use the supersymmetry to place lower bounds on the ground
state energy with various boundary conditions. For an odd number of sites in
the periodic chain, and with a particular boundary magnetic field in the open
chain, we can derive the ground state energy exactly. The supersymmetry thus
explains why it is possible to solve the Bethe equations for the ground state
in these cases. We also show that a similar space-time supersymmetry holds for
the t-J model at its integrable ferromagnetic point, where the space-time
supersymmetry and the Hamiltonian it yields coexist with a global u(1|2) graded
Lie algebra symmetry. Possible generalizations to other algebras are discussed.Comment: 12 page
Baxter operators for the quantum sl(3) invariant spin chain
The noncompact homogeneous sl(3) invariant spin chains are considered. We
show that the transfer matrix with generic auxiliary space is factorized into
the product of three sl(3) invariant commuting operators. These operators
satisfy the finite difference equations in the spectral parameters which follow
from the structure of the reducible sl(3) modules.Comment: 20 pages, 4 figures, references adde
Entanglement and correlation in anisotropic quantum spin systems
Analytical expressions for the entanglement measures concurrence,
i-concurrence and 3-tangle in terms of spin correlation functions are derived
using general symmetries of the quantum spin system. These relations are
exploited for the one-dimensional XXZ-model, in particular the concurrence and
the critical temperature for disentanglement are calculated for finite systems
with up to six qubits. A recent NMR quantum error correction experiment is
analyzed within the framework of the proposed theoretical approach.Comment: 8 pages, 3 figure
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