15,943 research outputs found
Magnetic hallmarks of viscous electron flow in graphene
We propose a protocol to identify spatial hallmarks of viscous electron flow
in graphene and other two-dimensional viscous electron fluids. We predict that
the profile of the magnetic field generated by hydrodynamic electron currents
flowing in confined geometries displays unambiguous features linked to
whirlpools and backflow near current injectors. We also show that the same
profile sheds light on the nature of the boundary conditions describing
friction exerted on the electron fluid by the edges of the sample. Our
predictions are within reach of vector magnetometry based on nitrogen-vacancy
centers embedded in a diamond slab mounted onto a graphene layer.Comment: 5 pages, 6 figure
Boundary correlation function of fixed-to-free bcc operators in square-lattice Ising model
We calculate the boundary correlation function of fixed-to-free boundary
condition changing operators in the square-lattice Ising model. The correlation
function is expressed in four different ways using block Toeplitz
determinants. We show that these can be transformed into a scalar Toeplitz
determinant when the size of the matrix is even. To know the asymptotic
behavior of the correlation function at large distance we calculate the
asymptotic behavior of this scalar Toeplitz determinant using the Szeg\"o's
theorem and the Fisher-Hartwig theorem. At the critical temperature we confirm
the power-law behavior of the correlation function predicted by conformal field
theory
Local-channel-induced rise of quantum correlations in continuous-variable systems
It was recently discovered that the quantum correlations of a pair of
disentangled qubits, as measured by the quantum discord, can increase solely
because of their interaction with a local dissipative bath. Here, we show that
a similar phenomenon can occur in continuous-variable bipartite systems. To
this aim, we consider a class of two-mode squeezed thermal states and study the
behavior of Gaussian quantum discord under various local Markovian non-unitary
channels. While these in general cause a monotonic drop of quantum
correlations, an initial rise can take place with a thermal-noise channel.Comment: 6 pages, 4 figure
Quantum Knizhnik-Zamolodchikov equation: reflecting boundary conditions and combinatorics
We consider the level 1 solution of quantum Knizhnik-Zamolodchikov equation
with reflecting boundary conditions which is relevant to the Temperley--Lieb
model of loops on a strip. By use of integral formulae we prove conjectures
relating it to the weighted enumeration of Cyclically Symmetric Transpose
Complement Plane Partitions and related combinatorial objects
Open boundary Quantum Knizhnik-Zamolodchikov equation and the weighted enumeration of Plane Partitions with symmetries
We propose new conjectures relating sum rules for the polynomial solution of
the qKZ equation with open (reflecting) boundaries as a function of the quantum
parameter and the -enumeration of Plane Partitions with specific
symmetries, with . We also find a conjectural relation \`a la
Razumov-Stroganov between the limit of the qKZ solution and refined
numbers of Totally Symmetric Self Complementary Plane Partitions.Comment: 27 pages, uses lanlmac, epsf and hyperbasics, minor revision
Quantum Information Encoding, Protection, and Correction from Trace-Norm Isometries
We introduce the notion of trace-norm isometric encoding and explore its
implications for passive and active methods to protect quantum information
against errors. Beside providing an operational foundations to the "subsystems
principle" [E. Knill, Phys. Rev. A 74, 042301 (2006)] for faithfully realizing
quantum information in physical systems, our approach allows additional
explicit connections between noiseless, protectable, and correctable quantum
codes to be identified. Robustness properties of isometric encodings against
imperfect initialization and/or deviations from the intended error models are
also analyzed.Comment: 10 pages, 1 figur
The Razumov-Stroganov conjecture: Stochastic processes, loops and combinatorics
A fascinating conjectural connection between statistical mechanics and
combinatorics has in the past five years led to the publication of a number of
papers in various areas, including stochastic processes, solvable lattice
models and supersymmetry. This connection, known as the Razumov-Stroganov
conjecture, expresses eigenstates of physical systems in terms of objects known
from combinatorics, which is the mathematical theory of counting. This note
intends to explain this connection in light of the recent papers by Zinn-Justin
and Di Francesco.Comment: 6 pages, 4 figures, JSTAT News & Perspective
Lattice two-point functions and conformal invariance
A new realization of the conformal algebra is studied which mimics the
behaviour of a statistical system on a discrete albeit infinite lattice. The
two-point function is found from the requirement that it transforms covariantly
under this realization. The result is in agreement with explicit lattice
calculations of the Ising model and the dimensional spherical
model. A hard core is found which is not present in the continuum. For a
semi-infinite lattice, profiles are also obtained.Comment: 5 pages, plain Tex with IOP macros, no figure
Polynomial solutions of qKZ equation and ground state of XXZ spin chain at Delta = -1/2
Integral formulae for polynomial solutions of the quantum
Knizhnik-Zamolodchikov equations associated with the R-matrix of the six-vertex
model are considered. It is proved that when the deformation parameter q is
equal to e^{+- 2 pi i/3} and the number of vertical lines of the lattice is
odd, the solution under consideration is an eigenvector of the inhomogeneous
transfer matrix of the six-vertex model. In the homogeneous limit it is a
ground state eigenvector of the antiferromagnetic XXZ spin chain with the
anisotropy parameter Delta equal to -1/2 and odd number of sites. The obtained
integral representations for the components of this eigenvector allow to prove
some conjectures on its properties formulated earlier. A new statement relating
the ground state components of XXZ spin chains and Temperley-Lieb loop models
is formulated and proved.Comment: v2: cosmetic changes, new section on refined TSSCPPs vs refined ASM
Hydrogen absorption properties of amorphous (Ni0.6Nb0.4−yTay)100−xZrx membranes
Ni based amorphous materials have great potential as hydrogen purification membranes. In the present work
the melt spun (Ni0.6Nb0.4−yTay)100−xZrx with y=0, 0.1 and x=20, 30 was studied. The result of X-ray diffraction
spectra of the ribbons showed an amorphous nature of the alloys. Heating these ribbons below T < 400 °C, even
in a hydrogen atmosphere (1−10 bar), the amorphous structure was retained. The crystallization process was
characterized by differential thermal analysis and the activation energy of such process was obtained. The
hydrogen absorption properties of the samples in their amorphous state were studied by the volumetric method,
and the results showed that the addition of Ta did not significantly influence the absorption properties, a clear
change of the hydrogen solubility was observed with the variation of the Zr content. The values of the
hydrogenation enthalpy changed from ~37 kJ/mol for x=30 to ~9 kJ/mol for x=20. The analysis of the
volumetric data provides the indications about the hydrogen occupation sites during hydrogenation, suggesting
that at the beginning of the absorption process the deepest energy levels are occupied, while only shallower
energy levels are available at higher hydrogen content, with the available interstitial sites forming a continuum
of energy levels
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