12,303 research outputs found
The effect of temperature evolution on the interior structure of HO-rich planets
For most planets in the range of radii from 1 to 4 R, water is a
major component of the interior composition. At high pressure HO can be
solid, but for larger planets, like Neptune, the temperature can be too high
for this. Mass and age play a role in determining the transition between solid
and fluid (and mixed) water-rich super-Earth. We use the latest high-pressure
and ultra-high-pressure phase diagrams of HO, and by comparing them
with the interior adiabats of various planet models, the temperature evolution
of the planet interior is shown, especially for the state of HO. It
turns out that the bulk of HO in a planet's interior may exist in
various states such as plasma, superionic, ionic, Ice VII, Ice X, etc.,
depending on the size, age and cooling rate of the planet. Different regions of
the mass-radius phase space are also identified to correspond to different
planet structures. In general, super-Earth-size planets (isolated or without
significant parent star irradiation effects) older than about 3 Gyr would be
mostly solid.Comment: Accepted by ApJ, in print for March 2014 (14 pages, 3 colored
figures, 1 table
Network Lasso: Clustering and Optimization in Large Graphs
Convex optimization is an essential tool for modern data analysis, as it
provides a framework to formulate and solve many problems in machine learning
and data mining. However, general convex optimization solvers do not scale
well, and scalable solvers are often specialized to only work on a narrow class
of problems. Therefore, there is a need for simple, scalable algorithms that
can solve many common optimization problems. In this paper, we introduce the
\emph{network lasso}, a generalization of the group lasso to a network setting
that allows for simultaneous clustering and optimization on graphs. We develop
an algorithm based on the Alternating Direction Method of Multipliers (ADMM) to
solve this problem in a distributed and scalable manner, which allows for
guaranteed global convergence even on large graphs. We also examine a
non-convex extension of this approach. We then demonstrate that many types of
problems can be expressed in our framework. We focus on three in particular -
binary classification, predicting housing prices, and event detection in time
series data - comparing the network lasso to baseline approaches and showing
that it is both a fast and accurate method of solving large optimization
problems
On the performance of two protocols: SARG04 and BB84
We compare the performance of BB84 and SARG04, the later of which was
proposed by V. Scarani et al., in Phys. Rev. Lett. 92, 057901 (2004).
Specifically, in this paper, we investigate SARG04 with two-way classical
communications and SARG04 with decoy states. In the first part of the paper, we
show that SARG04 with two-way communications can tolerate a higher bit error
rate (19.4% for a one-photon source and 6.56% for a two-photon source) than
SARG04 with one-way communications (10.95% for a one-photon source and 2.71%
for a two-photon source). Also, the upper bounds on the bit error rate for
SARG04 with two-way communications are computed in a closed form by considering
an individual attack based on a general measurement. In the second part of the
paper, we propose employing the idea of decoy states in SARG04 to obtain
unconditional security even when realistic devices are used. We compare the
performance of SARG04 with decoy states and BB84 with decoy states. We find
that the optimal mean-photon number for SARG04 is higher than that of BB84 when
the bit error rate is small. Also, we observe that SARG04 does not achieve a
longer secure distance and a higher key generation rate than BB84, assuming a
typical experimental parameter set.Comment: 48 pages, 10 figures, 1 column, changed Figs. 7 and
Supersymmetric Runge-Lenz-Pauli vector for Dirac vortex in topological insulators and graphene
The Dirac mass-vortex at the surface of a topological insulator or in
graphene is considered. Within the linear approximation for the vortex
amplitude's radial dependence, the spectrum is a series of degenerate bound
states, which can be classified by a set of accidental SU(2) and supersymmetry
generators (I. F. Herbut and C.-K. Lu, Phys. Rev. B 83 125412 (2011)). Here we
discuss further the properties and manifestations of the supersymmetry of the
vortex Hamiltonian, and point out some interesting analogies to the
Runge-Lenz-Pauli vector in the non-relativistic hydrogen atom. Symmetry
breaking effects due to a finite chemical potential, and the Zeeman field are
also analyzed. We find that a residual accidental degeneracy remains only in
the special case of equal magnitudes of both terms, whereas otherwise it
becomes removed entirely.Comment: revised version with added reference and a new paragraph on
interpretation of two-velocity Weyl fermions realized in 2D optical lattice;
to appear in J Phys
A balanced homodyne detector for high-rate Gaussian-modulated coherent-state quantum key distribution
We discuss excess noise contributions of a practical balanced homodyne
detector in Gaussian-modulated coherent-state (GMCS) quantum key distribution
(QKD). We point out the key generated from the original realistic model of GMCS
QKD may not be secure. In our refined realistic model, we take into account
excess noise due to the finite bandwidth of the homodyne detector and the
fluctuation of the local oscillator. A high speed balanced homodyne detector
suitable for GMCS QKD in the telecommunication wavelength region is built and
experimentally tested. The 3dB bandwidth of the balanced homodyne detector is
found to be 104MHz and its electronic noise level is 13dB below the shot noise
at a local oscillator level of 8.5*10^8 photon per pulse. The secure key rate
of a GMCS QKD experiment with this homodyne detector is expected to reach
Mbits/s over a few kilometers.Comment: 22 pages, 11 figure
Models of Social Groups in Blogosphere Based on Information about Comment Addressees and Sentiments
This work concerns the analysis of number, sizes and other characteristics of
groups identified in the blogosphere using a set of models identifying social
relations. These models differ regarding identification of social relations,
influenced by methods of classifying the addressee of the comments (they are
either the post author or the author of a comment on which this comment is
directly addressing) and by a sentiment calculated for comments considering the
statistics of words present and connotation. The state of a selected blog
portal was analyzed in sequential, partly overlapping time intervals. Groups in
each interval were identified using a version of the CPM algorithm, on the
basis of them, stable groups, existing for at least a minimal assumed duration
of time, were identified.Comment: Gliwa B., Ko\'zlak J., Zygmunt A., Models of Social Groups in
Blogosphere Based on Information about Comment Addressees and Sentiments, in
the K. Aberer et al. (Eds.): SocInfo 2012, LNCS 7710, pp. 475-488, Best Paper
Awar
Boundary K-matrices and the Lax pair for 1D open XYZ spin-chain
We analysis the symmetries of the reflection equation for open model
and find their solutions case by case. In the general open boundary
conditions, the Lax pair for open one-dimensional spin-chain is given.Comment: LaTeX, 17 pages, errors in references correcte
Security proof of a three-state quantum key distribution protocol without rotational symmetry
Standard security proofs of quantum key distribution (QKD) protocols often
rely on symmetry arguments. In this paper, we prove the security of a
three-state protocol that does not possess rotational symmetry. The three-state
QKD protocol we consider involves three qubit states, where the first two
states, |0_z> and |1_z>, can contribute to key generation and the third state,
|+>=(|0_z>+|1_z>)/\sqrt{2}, is for channel estimation. This protocol has been
proposed and implemented experimentally in some frequency-based QKD systems
where the three states can be prepared easily. Thus, by founding on the
security of this three-state protocol, we prove that these QKD schemes are, in
fact, unconditionally secure against any attacks allowed by quantum mechanics.
The main task in our proof is to upper bound the phase error rate of the qubits
given the bit error rates observed. Unconditional security can then be proved
not only for the ideal case of a single-photon source and perfect detectors,
but also for the realistic case of a phase-randomized weak coherent light
source and imperfect threshold detectors. Our result on the phase error rate
upper bound is independent of the loss in the channel. Also, we compare the
three-state protocol with the BB84 protocol. For the single-photon source case,
our result proves that the BB84 protocol strictly tolerates a higher quantum
bit error rate than the three-state protocol; while for the coherent-source
case, the BB84 protocol achieves a higher key generation rate and secure
distance than the three-state protocol when a decoy-state method is used.Comment: 10 pages, 3 figures, 2 column
Charge-density Waves Survive the Pauli Paramagnetic Limit
Measurements of the resistance of single crystals of (Per)Au(mnt)
have been made at magnetic fields of up to 45 T, exceeding the Pauli
paramagnetic limit of T. The continued presence of
non-linear charge-density wave electrodynamics at T unambiguously
establishes the survival of the charge-density wave state above the Pauli
paramagnetic limit, and the likely emergence of an inhomogeneous phase
analogous to that anticipated to occur in superconductors.Comment: 4 pages, three figure
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