59,280 research outputs found
The positive partial transpose conjecture for n=3
We present the PPT square conjecture introduced by M. Christandl. We prove
the conjecture in the case as a consequence of the fact that two-qutrit
PPT states have Schmidt at most two. Our result in Lemma 3 is independent from
the proof found M\"uller-Hermes. M\"uller-Hermes announced that this conjecture
is true for the states on \cite{hermes}
recently. The PPT square conjecture in the case is still open
Standardization, Distance, Host Galaxy Extinction of Type Ia Supernova and Hubble Diagram from the Flux Ratio Method
In this paper we generalize the flux ratio method Bailey et al. (2009) to the
case of two luminosity indicators and search the optimal luminosity-flux ratio
relations on a set of spectra whose phases are around not only the date of
bright light but also other time. With these relations, a new method is
proposed to constrain the host galaxy extinction of SN Ia and its distance. It
is first applied to the low redshift supernovas and then to the high redshift
ones. The results of the low redshift supernovas indicate that the flux ratio
method can indeed give well constraint on the host galaxy extinction parameter
E(B-V), but weaker constraints on R_{V}. The high redshift supernova spectra
are processed by the same method as the low redshift ones besides some
differences due to their high redshift. Among 16 high redshift supernovas, 15
are fitted very well except 03D1gt. Based on these distances, Hubble diagram is
drew and the contents of the Universe are analyzed. It supports an acceleration
behavior in the late Universe. Therefore, the flux ratio method can give
constraints on the host galaxy extinction and supernova distance independently.
We believe, through further studies, it may provide a precise tool to probe the
acceleration of the Universe than before.Comment: 33 pages, 9 figures and 6 table
Doubly Stochastic Primal-Dual Coordinate Method for Bilinear Saddle-Point Problem
We propose a doubly stochastic primal-dual coordinate optimization algorithm
for empirical risk minimization, which can be formulated as a bilinear
saddle-point problem. In each iteration, our method randomly samples a block of
coordinates of the primal and dual solutions to update. The linear convergence
of our method could be established in terms of 1) the distance from the current
iterate to the optimal solution and 2) the primal-dual objective gap. We show
that the proposed method has a lower overall complexity than existing
coordinate methods when either the data matrix has a factorized structure or
the proximal mapping on each block is computationally expensive, e.g.,
involving an eigenvalue decomposition. The efficiency of the proposed method is
confirmed by empirical studies on several real applications, such as the
multi-task large margin nearest neighbor problem
Energy-efficient Analytics for Geographically Distributed Big Data
Big data analytics on geographically distributed datasets (across data
centers or clusters) has been attracting increasing interests from both
academia and industry, but also significantly complicates the system and
algorithm designs. In this article, we systematically investigate the
geo-distributed big-data analytics framework by analyzing the fine-grained
paradigm and the key design principles. We present a dynamic global manager
selection algorithm (GMSA) to minimize energy consumption cost by fully
exploiting the system diversities in geography and variation over time. The
algorithm makes real-time decisions based on the measurable system parameters
through stochastic optimization methods, while achieving the performance
balances between energy cost and latency. Extensive trace-driven simulations
verify the effectiveness and efficiency of the proposed algorithm. We also
highlight several potential research directions that remain open and require
future elaborations in analyzing geo-distributed big data
Chemical Bondings Induced Rich Electronic Properties of Oxygen Absorbed Few-layer Graphenes
Electronic properties of graphene oxides enriched by the strong chemical
bondings are investigated using first-principle calculations. They are very
sensitive to the changes in the number of graphene layer, stacking
configuration, and distribution of oxygen. The feature-rich electronic
structures exhibit the destruction or distortion of Dirac cone, opening of band
gap, anisotropic energy dispersions, O- and (C,O)-dominated energy dispersions,
and extra critical points. All the few-layer graphene oxides are semi-metals
except for the semiconducting monolayer ones. For the former, the distorted
Dirac-cone structures and the O-dominated energy bands near the Fermi level are
revealed simultaneously. The orbital-projected density of states (DOS) have
many special structures mainly coming from a composite energy band, the
parabolic and partially flat ones. The DOS and spatial charge distributions
clearly indicate the critical bondings in O-O, C-O and C-C bonds, being
responsible for the diversified properties
Secrecy Energy Efficiency Maximization for UAV-Enabled Mobile Relaying
This paper investigates the secrecy energy efficiency (SEE) maximization
problem for unmanned aerial vehicle enabled mobile relaying system, where a
high-mobility UAV is exploited to assist delivering the confidential
information from a ground source to a legitimate ground destination with the
direct link blocked, in the presence of a potential eavesdropper. We aim to
maximize SEE of the UAV by jointly optimizing the communication scheduling,
power allocation, and UAV trajectory over a finite time horizon. The formulated
problem is a mixed-integer non-convex optimization problem that is challenging
to be solved optimally. To make the problem tractable, we decompose the problem
into three subproblems, and propose an efficient iterative algorithm that
alternately optimizes the subproblems. In addition, two special cases are
considered as benchmarks in this paper. Simulation results show that the
proposed design significantly improves the SEE of the UAV, as compared to the
benchmarksComment: 22pages 7figures for possible journal submissio
-variational problems associated to measurable Finsler structures
We study -variational problems associated to measurable Finsler
structures in Euclidean spaces. We obtain existence and uniqueness results for
the absolute minimizers.Comment: 15 pages. arXiv admin note: text overlap with arXiv:1305.6130 by
other author
Singlet States Preparation for Three -type Atoms with Rydberg Blockade Mechanism
A proposal for the generation of singlet states of three -type
Rydberg atoms is presented. The singlet state is prepared through the
combination of a Rydberg state and an EPR pair, and the scheme relies on the
Rydberg blockade effect which prevents the simultaneous excitation of the two
atoms to a Rydberg state. In addition, some frequency detuning between lasers
and atomic transitions is set to eliminate the degenerate of the two ground
states. And finally, a series of numerical simulations are made to show the
feasibility of the scheme.Comment: 8 pages,5 figure
Fluorination-Enriched Electronic and Magnetic Properties in Graphene Nanoribbons
The feature-rich electronic and magnetic properties of fluorine-doped
graphene nanoribbons are investigated by the first-principles calculations.
They arise from the cooperative or competitive relations among the significant
chemical bonds, finite-size quantum confinement and edge structure. There exist
C-C, C-F, and F-F bonds with the multi-orbital hybridizations. Fluorine adatoms
can create the p-type metals or the concentration- and distribution-dependent
semiconductors, depending on whether the bonding is seriously suppressed
by the top-site chemical bonding. Furthermore, five kinds of spin-dependent
electronic and magnetic properties cover the non-magnetic and ferromagnetic
metals, the non-magnetic semiconductors, and the anti-ferromagnetic
semiconductors with/without the spin splitting. The diverse essential
properties are clearly revealed in the spatial charge distribution, the spin
density, and the orbital-projected density of states
Master equation approach to transient quantum transport incorporating with initial correlations
In this paper, the exact transient quantum transport of non-interacting
nanostructures is investigated in the presence of initial system-lead
correlations and initial lead-lead correlations for a device system coupled to
general electronic leads. The exact master equation incorporating with initial
correlations is derived through the extended quantum Langevin equation. The
effects of the initial correlations are manifested through the time-dependent
fluctuations contained explicitly in the exact master equation. The transient
transport current incorporating with initial correlations is obtained from the
exact master equation. The resulting transient transport current can be
expressed in terms of the single-particle propagating and correlation Green
functions of the device system. We show that the initial correlations can
affect quantum transport not only in the transient regime, but also in the
steady-state limit when system-lead couplings are strong enough so that
electron localized bound states occur in the device system.Comment: 13pages, 4figure
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