39,545 research outputs found
A deep learning approach to diabetic blood glucose prediction
We consider the question of 30-minute prediction of blood glucose levels
measured by continuous glucose monitoring devices, using clinical data. While
most studies of this nature deal with one patient at a time, we take a certain
percentage of patients in the data set as training data, and test on the
remainder of the patients; i.e., the machine need not re-calibrate on the new
patients in the data set. We demonstrate how deep learning can outperform
shallow networks in this example. One novelty is to demonstrate how a
parsimonious deep representation can be constructed using domain knowledge
Generic canonical form of pairs of matrices with zeros
We consider a family of pairs of m-by-p and m-by-q matrices, in which some
entries are required to be zero and the others are arbitrary, with respect to
transformations (A,B)--> (SAR,SBL) with nonsingular S, R, L. We prove that
almost all of these pairs reduce to the same pair (C, D) from this family,
except for pairs whose arbitrary entries are zeros of a certain polynomial. The
polynomial and the pair (C D) are constructed by a combinatorial method based
on properties of a certain graph.Comment: 13 page
Mesoscopic threshold detectors: Telegraphing the size of a fluctuation
We propose a two-terminal method to measure shot noise in mesoscopic systems
based on an instability in the current-voltage characteristic of an on-chip
detector. The microscopic noise drives the instability, which leads to random
switching of the current between two values, the telegraph process. In the
Gaussian regime, the shot noise power driving the instability may be extracted
from the I-V curve, with the noise power as a fitting parameter. In the
threshold regime, the extreme value statistics of the mesoscopic conductor can
be extracted from the switching rates, which reorganize the complete
information about the current statistics in an indirect way, "telegraphing" the
size of a fluctuation. We propose the use of a quantum double dot as a
mesoscopic threshold detector.Comment: 9 pages, 7 figures, published versio
Gravitational-Wave Astronomy with Inspiral Signals of Spinning Compact-Object Binaries
Inspiral signals from binary compact objects (black holes and neutron stars)
are primary targets of the ongoing searches by ground-based gravitational-wave
interferometers (LIGO, Virgo, GEO-600 and TAMA-300). We present
parameter-estimation simulations for inspirals of black-hole--neutron-star
binaries using Markov-chain Monte-Carlo methods. For the first time, we have
both estimated the parameters of a binary inspiral source with a spinning
component and determined the accuracy of the parameter estimation, for
simulated observations with ground-based gravitational-wave detectors. We
demonstrate that we can obtain the distance, sky position, and binary
orientation at a higher accuracy than previously suggested in the literature.
For an observation of an inspiral with sufficient spin and two or three
detectors we find an accuracy in the determination of the sky position of
typically a few tens of square degrees.Comment: v2: major conceptual changes, 4 pages, 1 figure, 1 table, submitted
to ApJ
Optical spectra of the heavy fermion uniaxial ferromagnet UGe
We report a detailed study of UGe single crystals using infrared
reflectivity and spectroscopic ellipsometry. The optical conductivity suggests
the presence of a low frequency interband transition and a narrow free-carrier
response with strong frequency dependence of the scattering rate and effective
mass. We observe sharp changes in the low frequency mass and scattering rate
below the upper ferromagnetic transition . The characteristic
changes are exhibited most strongly at an energy scale of around 12 meV (100
cm). They recover their unrenormalized value above and for 40 meV. In contrast no sign of an anomaly is seen at the lower transition
temperature of unknown nature 30 K, observed in transport and
thermodynamic experiments. In the ferromagnetic state we find signatures of a
strong coupling to the longitudinal magnetic excitations that have been
proposed to mediate unconventional superconductivity in this compound
The two colors of MgB2
We present the anisotropic optical conductivity of MgB between 0.1 and
3.7 eV at room temperature obtained on single crystals of different purity by
the spectroscopic ellipsometry and reflectance measurements. The bare
(unscreened) plasma frequency is almost isotropic and equal to 6.3
eV, which contrasts some earlier reports of a very small value of .
The data suggests that the -bands are characterized by a stronger
electron-phonon coupling but smaller impurity scattering
, compared to the -bands. The optical response along the
boron planes is marked by an intense interband transition at 2.6 eV, due to
which the reflectivity plasma edges along the a- and c-axes are shifted with
respect to each other. As a result, the sample spectacularly changes color from
a blueish-silver to the yellow as the polarization is rotated from the in-plane
direction towards the c-axis. The optical spectra are in good agreement with
the published {\it ab initio} calculations. The remaining discrepancies can be
explained by the relative shift of -bands and -bands by about 0.2
eV compared to the theoretical band structure, in agreement with the de
Haas-van Alphen experiments. The widths of the Drude and the interband peaks
are both very sensitive to the sample purity.Comment: 11 pages, 13 figure
Parafermions, parabosons and representations of so(\infty) and osp(1|\infty)
The goal of this paper is to give an explicit construction of the Fock spaces
of the parafermion and the paraboson algebra, for an infinite set of
generators. This is equivalent to constructing certain unitary irreducible
lowest weight representations of the (infinite rank) Lie algebra so(\infty) and
of the Lie superalgebra osp(1|\infty). A complete solution to the problem is
presented, in which the Fock spaces have basis vectors labelled by certain
infinite but stable Gelfand-Zetlin patterns, and the transformation of the
basis is given explicitly. We also present expressions for the character of the
Fock space representations
Universality check of Abelian Monopoles
We study the Abelian projected SU(2) lattice gauge theory after gauge fixing
to the maximally Abelian gauge (MAG). In order to check the universality of the
Abelian dominance we employ the tadpole improved tree level (TI) action. We
show that the density of monopoles in the largest cluster (the IR component) is
finite in the continuum limit which is approximated already at relatively large
lattice spacing. The value itself is smaller than in the case of Wilson action.
We present results for the ratio of the Abelian to non-Abelian string tension
for both Wilson and TI actions for a number of lattice spacings in the range
0.06 fm < a < 0.35 fm. These results show that the ratio is between 0.9 and
0.95 for all considered values of lattice couplings and both actions. We
compare the properties of the monopole clusters in two gauges - in MAG and in
the Laplacian Abelian gauge (LAG). Whereas in MAG the infrared component of the
monopole density shows a good convergence to the continuum limit, we find that
in LAG it is even not clear whether a finite limit exists.Comment: 18 pages, 11 figure
Phonon Rabi-assisted tunneling in diatomic molecules
We study electronic transport in diatomic molecules connected to metallic
contacts in the regime where both electron-electron and electron-phonon
interactions are important. We find that the competition between these
interactions results in unique resonant conditions for interlevel transitions
and polaron formation: the Coulomb repulsion requires additional energy when
electrons attempt phonon-assisted interlevel jumps between fully or partially
occupied levels. We apply the equations of motion approach to calculate the
electronic Green's functions. The density of states and conductance through the
system are shown to exhibit interesting Rabi-like splitting of Coulomb blockade
peaks and strong temperature dependence under the it interacting resonant
conditions.Comment: Updated version, 5 pages, 4 figures, to be published in Phys. Rev. B
on 9/1
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