722 research outputs found
Food Ingredients Recognition through Multi-label Learning
Automatically constructing a food diary that tracks the ingredients consumed
can help people follow a healthy diet. We tackle the problem of food
ingredients recognition as a multi-label learning problem. We propose a method
for adapting a highly performing state of the art CNN in order to act as a
multi-label predictor for learning recipes in terms of their list of
ingredients. We prove that our model is able to, given a picture, predict its
list of ingredients, even if the recipe corresponding to the picture has never
been seen by the model. We make public two new datasets suitable for this
purpose. Furthermore, we prove that a model trained with a high variability of
recipes and ingredients is able to generalize better on new data, and visualize
how it specializes each of its neurons to different ingredients.Comment: 8 page
Chiral symmetry analysis and rigid rotational invariance for the lattice dynamics of single-wall carbon nanotubes
In this paper, we provide a detailed expression of the vibrational potential
for the lattice dynamics of the single-wall carbon nanotubes (SWCNT) satisfying
the requirements of the exact rigid translational as well as rotational
symmetries, which is a nontrivial generalization of the valence force model for
the planar graphene sheet. With the model, the low frequency behavior of the
dispersion of the acoustic modes as well as the flexure mode can be precisely
calculated. Based upon a comprehensive chiral symmetry analysis, the calculated
mode frequencies (including all the Raman and infrared active modes),
velocities of acoustic modes and the polarization vectors are systematically
fitted in terms of the chiral angle and radius, where the restrictions of
various symmetry operations of the SWCNT are fulfilled
Quantization of Lie-Poisson structures by peripheric chains
The quantization properties of composite peripheric twists are studied.
Peripheric chains of extended twists are constructed for U(sl(N)) in order to
obtain composite twists with sufficiently large carrier subalgebras. It is
proved that the peripheric chains can be enlarged with additional Reshetikhin
and Jordanian factors. This provides the possibility to construct new solutions
to Drinfeld equations and, thus, to quantize new sets of Lie-Poisson
structures. When the Jordanian additional factors are used the carrier algebras
of the enlarged peripheric chains are transformed into algebras of motion of
the form G_{JB}^{P}={G}_{H}\vdash {G}_{P}. The factor algebra G_{H} is a direct
sum of Borel and contracted Borel subalgebras of lower dimensions. The
corresponding omega--form is a coboundary. The enlarged peripheric chains
F_{JB}^{P} represent the twists that contain operators external with respect to
the Lie-Poisson structure. The properties of new twists are illustrated by
quantizing r-matrices for the algebras U(sl(3)), U(sl(4)) and U(sl(7)).Comment: 24 pages, LaTe
Twist maps for non-standard quantum algebras and discrete Schrodinger symmetries
The minimal twist map introduced by B. Abdesselam, A. Chakrabarti, R.
Chakrabarti and J. Segar (Mod. Phys. Lett. A 14 (1999) 765) for the
non-standard (Jordanian) quantum sl(2,R) algebra is used to construct the twist
maps for two different non-standard quantum deformations of the (1+1)
Schrodinger algebra. Such deformations are, respectively, the symmetry algebras
of a space and a time uniform lattice discretization of the (1+1) free
Schrodinger equation. It is shown that the corresponding twist maps connect the
usual Lie symmetry approach to these discrete equations with non-standard
quantum deformations. This relationship leads to a clear interpretation of the
deformation parameter as the step of the uniform (space or time) lattice.Comment: 16 pages, LaTe
(1+1) Schrodinger Lie bialgebras and their Poisson-Lie groups
All Lie bialgebra structures for the (1+1)-dimensional centrally extended
Schrodinger algebra are explicitly derived and proved to be of the coboundary
type. Therefore, since all of them come from a classical r-matrix, the complete
family of Schrodinger Poisson-Lie groups can be deduced by means of the
Sklyanin bracket. All possible embeddings of the harmonic oscillator, extended
Galilei and gl(2) Lie bialgebras within the Schrodinger classification are
studied. As an application, new quantum (Hopf algebra) deformations of the
Schrodinger algebra, including their corresponding quantum universal
R-matrices, are constructed.Comment: 25 pages, LaTeX. Possible applications in relation with integrable
systems are pointed; new references adde
Phonon and plasmon excitation in inelastic electron tunneling spectroscopy of graphite
The inelastic electron tunneling spectrum (IETS)of highly oriented pyrolitic
graphite (HOPG) has been measured with scanning tunneling spectroscopy (STS) at
6K. The observed spectral features are in very good agreement with the
vibrational density of states (vDOS) of graphite calculated from first
principles. We discuss the enhancement of certain phonon modes by
phonon-assisted tunneling in STS based on the restrictions imposed by the
electronic structure of graphite. We also demonstrate for the first time the
local excitation of surface-plasmons in IETS which are detected at an energy of
40 meV.Comment: PRB rapid communication, submitte
Twisted Conformal Algebra so(4,2)
A new twisted deformation, U_z(so(4,2)), of the conformal algebra of the
(3+1)-dimensional Minkowskian spacetime is presented. This construction is
provided by a classical r-matrix spanned by ten Weyl-Poincare generators, which
generalizes non-standard quantum deformations previously obtained for so(2,2)
and so(3,2). However, by introducing a conformal null-plane basis it is found
that the twist can indeed be supported by an eight-dimensional carrier
subalgebra. By construction the Weyl-Poincare subalgebra remains as a Hopf
subalgebra after deformation. Non-relativistic limits of U_z(so(4,2)) are shown
to be well defined and they give rise to new twisted conformal algebras of
Galilean and Carroll spacetimes. Furthermore a difference-differential massless
Klein-Gordon (or wave) equation with twisted conformal symmetry is constructed
through deformed momenta and position operators. The deformation parameter is
interpreted as the lattice step on a uniform Minkowskian spacetime lattice
discretized along two basic null-plane directions.Comment: 20 pages, LaTe
Non-relativistic metrics with extremal limits
We present solutions of type IIB supergravity with z=2 Schrodinger
asymptotics that admit an extremal limit, i.e. the black hole horizon has a
double zero. These solutions are obtained as TsT transformations of the charged
planar black hole in AdS_5 \times S^5. Unlike the uncharged solution, the
Ramond-Ramond two-form is turned on. We study the thermodynamic properties of
these new solutions, and we show that the ratio of shear viscosity to entropy
density is 1/4\pi even in the extremal limit. We also consider the
TsT-transformed soliton and show that, for a special radius of the compact
circle, there is a confinement-deconfinement phase transition at zero
temperature between the soliton and black hole phases.Comment: 23 pages, references and clarifications added, typos corrected,
restriction in phase transition due to equation 6.5 emphasized; published
versio
Study of the electron-phonon interaction in metal diborides MeB_2 (Me=Zr, Nb, Ta, Mg) by point-contact spectroscopy
We review investigations of the electron-phonon interaction (EPI) in metal
diborides MeB_2 (Me=Zr, Nb, Ta, Mg) by point-contact (PC) spectroscopy. For
transition metal compounds the PC EPI functions were recovered and EPI
parameter were estimated. The data are consistent with
the measured surface phonon dispersion curves. The low value
questions some reports about superconductivity in these compounds. Contrary,
EPI in superconducting MgB_2 films manifests also in the PC spectra itself by
virtue of an elastic EPI contribution to the excess current determined by the
energy dependence of the superconducting order parameter. To analyse the phonon
features in the PC spectra of MgB a two-band model is exploited and the
proximity effect in the {\bf k}-space is suggested.Comment: 6 pages, 6 figs., prepared for proceedings of conference "Modern
Problem in Superconductivity", Sept. 2002, Yalta, Ukrain
Duality for Exotic Bialgebras
In the classification of Hietarinta, three triangular
-matrices lead, via the FRT formalism, to matrix bialgebras which are not
deformations of the trivial one. In this paper, we find the bialgebras which
are in duality with these three exotic matrix bialgebras. We note that the
duality of FRT is not sufficient for the construction of the bialgebras
in duality. We find also the quantum planes corresponding to these bialgebras
both by the Wess-Zumino R-matrix method and by Manin's method.Comment: 25 pages, LaTeX2e, using packages: cite, amsfonts, amsmath, subeq
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