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Sep 23, 2013
09/13

by
Fabrizio Buscemi; Paolo Bordone

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We describe an efficient theoretical criterion suitable for the evaluation of the tripartite entanglement of any mixed three-boson or -fermion state, based on the notion of the entanglement of particles for bipartite systems of identical particles. Our approach allows one to quantify the accessible amount of quantum correlations in the systems without any violation of the local particle number superselection rule. A generalization of the tripartite negativity is here applied to some correlated...

Source: http://arxiv.org/abs/1105.4061v1

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Sep 19, 2013
09/13

by
Minoru Itoh

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This article presents a natural extension of the tensor algebra. In addition to "left multiplications" by vectors, we can consider "derivations" by covectors as basic operators on this extended algebra. These two types of operators satisfy an analogue of the canonical commutation relations. This algebra and these operators have some applications: (i) applications to invariant theory related to tensor products, and (ii) applications to immanants. The latter one includes a new...

Source: http://arxiv.org/abs/0909.5586v4

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Sep 23, 2013
09/13

by
S. M. Barr

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In the absence of low-energy supersymmetry, a multiplicity of weak-scale Higgs doublets would require additional fine-tunings unless they formed an irreducible multiplet of a non-abelian symmetry. Remnants of such symmetry typically render some Higgs fields stable, giving several dark matter particles of various masses. The non-abelian symmetry also typically gives simple, testable mass relations.

Source: http://arxiv.org/abs/1105.2085v2

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Sep 22, 2013
09/13

by
Simone Bux; Christine Gnahm; Reinhardt A. W. Maier; Claus Zimmermann; Philippe W. Courteille

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We study collective scattering with Bose-Einstein condensates interacting with a high-finesse ring cavity. The condensate scatters the light of a transverse pump beam superradiantly into modes which, in contrast to previous experiments, are not determined by the geometrical shape of the condensate, but specified by a resonant cavity mode. Moreover, since the recoil-shifted frequency of the scattered light depends on the initial momentum of the scattered fraction of the condensate, we show that...

Source: http://arxiv.org/abs/1101.2391v2

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Sep 23, 2013
09/13

by
Andrew Schumann; Andrew Adamatzky

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We propose a novel model of unconventional computing where a structural part of computation is presented by dynamics of plasmodium of Physarum polycephalum, a large single cell. We sketch a new logical approach combining conventional logic with process calculus to demonstrate how to employ formal methods in design of unconventional computing media presented by Physarum polycephalum.

Source: http://arxiv.org/abs/1105.4060v1

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Sep 23, 2013
09/13

by
Dan Ciubotaru

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We give a common framework for the classification of projective spin irreducible representations of a Weyl group, modeled after the Springer correspondence for ordinary representations.

Source: http://arxiv.org/abs/1006.3823v2

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Sep 23, 2013
09/13

by
Robert Alkins; Vesko Valov

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We describe the supports of a class of real-valued maps on $C*(X)$ introduced by Radul. Using this description, a characterization of compact-valued retracts of a given space in terms of functional extenders is obtained. For example, if $X\subset Y$, then there exists a continuous compact-valued retraction from $Y$ onto $X$ if and only if there exists a normed weakly additive extender $u\colon C*(X)\to C*(Y)$ with compact supports preserving $\min$ (resp., $\max$) and weakly preserving $\max$...

Source: http://arxiv.org/abs/1105.4122v1

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Sep 23, 2013
09/13

by
I. S. Maksymov; A. R. Davoyan; C. Simovski; P. Belov; Yu. S. Kivshar

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We suggest a novel multifrequency broadband plasmonic Yagi-Uda-type nanoantenna equipped with an array of tapered directors. Each director can be used for the excitation of the antenna by nanoemitters matched spectrally with the director resonant frequency and placed in the director near-field region. Multifrequency op- eration of nanoantennas provides tremendous opportunities for broadband emission enhancement, spectroscopy and sensing. By the principle of reciprocity, the same tapered...

Source: http://arxiv.org/abs/1105.4197v1

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Sep 23, 2013
09/13

by
Beth A. Reid; Martin White

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Observations of redshift-space distortions in spectroscopic galaxy surveys offer an attractive method for measuring the build-up of cosmological structure, which depends both on the expansion rate of the Universe and our theory of gravity. Galaxies occupy dark matter halos, whose redshift space clustering has a complex dependence on bias that cannot be inferred from the behavior of matter. We identify two distinct corrections on quasilinear scales (~ 30-80 Mpc/h): the non-linear mapping between...

Source: http://arxiv.org/abs/1105.4165v1

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Sep 23, 2013
09/13

by
Dirk Pauly; Sergey Repin

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This paper is concerned with the derivation of computable and guaranteed upper and lower bounds of the difference between the exact and the approximate solution of a boundary value problem for static Maxwell equations. Our analysis is based upon purely functional argumentation and does not attract specific properties of an approximation method. Therefore, the estimates derived in the paper at hand are applicable to any approximate solution that belongs to the corresponding energy space. Such...

Source: http://arxiv.org/abs/1105.4107v1

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Sep 19, 2013
09/13

by
Worasom Kundhikanjana; Keji Lai; Michael A. Kelly; Zhi-Xun Shen

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We report the instrumentation and experimental results of a cryogenic scanning microwave impedance microscope. The microwave probe and the scanning stage are located inside the variable temperature insert of a helium cryostat. Microwave signals in the distance modulation mode are used for monitoring the tip-sample distance and adjusting the phase of the two output channels. The ability to spatially resolve the metal-insulator transition in a doped silicon sample is demonstrated. The data agree...

Source: http://arxiv.org/abs/1010.1509v2

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Sep 23, 2013
09/13

by
Hamid Torabi; Ali Pakdaman; Behrooz Mashayekhy

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In this paper, we show that the image of the topological fundamental group of a given space $X$ is dense in the topological fundamental group of the quotient space $X/A$ under the induced homomorphism of the quotient map, where $A$ is a suitable subspace of $X$ with some conditions on $X$. Also, we give some application to find out some properties for $\pi_1^{top}(X/A,*)$. In particular, we give some condition in which $\pi_1^{top}(X/A,*)$ is an indiscrete topological group.

Source: http://arxiv.org/abs/1105.4009v1

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Sep 23, 2013
09/13

by
G. Faldt; C. Wilkin

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Evidence has recently been presented for the existence of a dibaryon of mass 2380 MeV/c^2 and width 70 MeV/c^2, which decays strongly into the d pi0 pi0 channel [M. Bashkanov et al., Phys.Rev.Lett. 102 (2009) 052301; P. Adlarson et al., arXiv:1104.0123]. The decay rate of such a hypothesised dibaryon into the {pn}_{I=0} pi0 pi0 channel is estimated in a weakly model-dependent way by using final state interaction theory. It is shown that, if the resonance exists, it should then show up as...

Source: http://arxiv.org/abs/1105.4142v1

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Sep 23, 2013
09/13

by
Zhen Liu; Qian-Ming Zhang; Linyuan Lü; Tao Zhou

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Common-neighbor-based method is simple yet effective to predict missing links, which assume that two nodes are more likely to be connected if they have more common neighbors. In such method, each common neighbor of two nodes contributes equally to the connection likelihood. In this Letter, we argue that different common neighbors may play different roles and thus lead to different contributions, and propose a local na\"{\i}ve Bayes model accordingly. Extensive experiments were carried out...

Source: http://arxiv.org/abs/1105.4005v1

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Sep 18, 2013
09/13

by
Saikat Guha; Ivan Savov; Mark M. Wilde

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Semiclassical models for multiple-user optical communication cannot assess the ultimate limits on reliable communication as permitted by the laws of physics. In all optical communications settings that have been analyzed within a quantum framework so far, the gaps between the quantum limit to the capacity and the Shannon limit for structured receivers become most significant in the low photon-number regime. Here, we present a quantum treatment of a multiple-transmitter multiple-receiver...

Source: http://arxiv.org/abs/1102.2627v2

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Sep 23, 2013
09/13

by
Simon R. Huisman; Rajesh V. Nair; Léon A. Woldering; Merel D. Leistikow; Allard P. Mosk; Willem L. Vos

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We have studied the reflectivity of CMOS-compatible three-dimensional silicon inverse woodpile photonic crystals at near-infrared frequencies. Polarization-resolved reflectivity spectra were obtained from two orthogonal crystal surfaces corresponding to 1.88 pi sr solid angle. The spectra reveal broad peaks with high reflectivity up to 67 % that are independent of the spatial position on the crystals. The spectrally overlapping reflectivity peaks for all directions and polarizations form the...

Source: http://arxiv.org/abs/1012.5263v2

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Sep 19, 2013
09/13

by
P. M. R. Brydon; Yasuhiro Asano; Carsten Timm

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A thin ferromagnetic layer on a bulk equal-spin-pairing triplet superconductor is shown to mediate a Josephson coupling between the spin $\uparrow$ and $\downarrow$ condensates of the superconductor. By deriving analytic expressions for the bound states at the triplet superconductor-ferromagnet interface, we show that this spin Josephson effect establishes an effective anisotropy axis in the ferromagnetic layer. The associated Josephson spin current is predicted to cause a measurable precession...

Source: http://arxiv.org/abs/1010.4238v2

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Sep 22, 2013
09/13

by
Michael Kesden

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A test particle of mass mu on a bound geodesic of a Kerr black hole of mass M >> mu will slowly inspiral as gravitational radiation extracts energy and angular momentum from its orbit. This inspiral can be considered adiabatic when the orbital period is much shorter than the timescale on which energy is radiated, and quasi-circular when the radial velocity is much less than the azimuthal velocity. Although the inspiral always remains adiabatic provided mu < < M, the quasi-circular...

Source: http://arxiv.org/abs/1101.3749v2

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Sep 22, 2013
09/13

by
Jose-Luis Lopez; Ricardo Lopez-Ruiz; Xavier Calbet

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In simulations of some economic gas-like models, the asymptotic regime shows an exponential wealth distribution, independently of the initial wealth distribution given to the system. The appearance of this statistical equilibrium for this type of gas-like models is explained in a rigorous analytical way.

Source: http://arxiv.org/abs/1103.5703v3

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Sep 23, 2013
09/13

by
Mihai Turinici

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The comparison type version of the fixed point result in ordered metric spaces established by Nieto and Rodriguez-Lopez [Acta Math. Sinica (English Series), 23 (2007), 2205-2212] is nothing but a particular case of the classical Banach's contraction principle [Fund. Math., 3 (1922), 133-181].

Source: http://arxiv.org/abs/1105.2401v2

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Sep 23, 2013
09/13

by
G. Odriozola; F. de J. Guevara-Rodríguez

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We implemented the replica exchange Monte Carlo technique to produce the equation of state of hard 1:5 aspect-ratio oblate ellipsoids for a wide density range. For this purpose, we considered the analytical approximation of the overlap distance given by Bern and Pechukas and the exact numerical solution given by Perram and Wertheim. For both cases we capture the expected isotropic-nematic transition at low densities and a nematic-crystal transition at larger densities. For the exact case, these...

Source: http://arxiv.org/abs/1105.2789v3

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Sep 23, 2013
09/13

by
Taylor L. Hughes; Andrew Randono

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It is generally assumed that the gravitational field is bosonic. Here we show that a simple propagating torsional theory can give rise to localized geometric structures that can consistently be quantized as fermions under exchange. To demonstrate this, we show that the model can be formally mapped onto the Skyrme model of baryons, and we use well-known results from Skyrme theory. This begs the question: {\it Is geometry bosonic or fermionic (or both)?}

Source: http://arxiv.org/abs/1105.4184v1

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Sep 23, 2013
09/13

by
A. A. Gvozdev; I. S. Ognev; E. V. Osokina

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Based on the magnetar model, we have studied in detail the processes of neutrino cooling of an electron--positron plasma generating an SGR giant flare and the influence of the magnetar magnetic field on these processes. Electron--positron pair annihilation and synchrotron neutrino emission are shown to make a dominant contribution to the neutrino emissivity of such a plasma. We have calculated the neutrino energy losses from a plasma-filled region at the long tail stage of the SGR 0526--66, SGR...

Source: http://arxiv.org/abs/1105.4080v1

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Sep 23, 2013
09/13

by
E. A. Provornikova; V. V. Izmodenov; R. Lallement

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We present a two-component gasdynamic model of an interstellar cloud embedded in a hot plasma. It is assumed that the cloud consists of atomic hydrogen gas, interstellar plasma is quasineutral. Hydrogen atoms and plasma protons interact through a charge exchange process. Magnetic felds and radiative processes are ignored in the model. The influence of heat conduction within plasma on the interaction between a cloud and plasma is studied. We consider the extreme case and assume that hot plasma...

Source: http://arxiv.org/abs/1105.4187v1

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Sep 21, 2013
09/13

by
Marco Mamone-Capria

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The concept of an objective spatial direction in special relativity is investigated and theories assuming light-speed isotropy while accepting the existence of a privileged spatial direction are classified. A natural generalization of the proper time principle is introduced which makes it possible to devise experimental tests of spatial isotropy. Several common misunderstandings in the relativistic literature concerning the role of spatial isotropy are clarified.

Source: http://arxiv.org/abs/1008.3619v4

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Sep 23, 2013
09/13

by
Yuji Kodama; Lauren Williams

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Soliton solutions of the KP equation have been studied since 1970, when Kadomtsev and Petviashvili proposed a two-dimensional nonlinear dispersive wave equation now known as the KP equation. It is well-known that the Wronskian approach to the KP equation provides a method to construct soliton solutions. The regular soliton solutions that one obtains in this way come from points of the totally non-negative part of the Grassmannian. In this paper we explain how the theory of total positivity and...

Source: http://arxiv.org/abs/1105.4170v1

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Sep 23, 2013
09/13

by
Dirk Pauly; Sergey Repin; Tuomo Rossi

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In this paper, we consider an initial boundary value problem for Maxwell's equations. For this hyperbolic type problem, we derive guaranteed and computable upper bounds for the difference between the exact solution and any pair of vector fields in the space-time cylinder that belongs to the corresponding admissible energy class. For this purpose, we use a method suggested earlier for the wave equation.

Source: http://arxiv.org/abs/1105.4110v1

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Sep 23, 2013
09/13

by
Rocio Gonzalez-Diaz; Maria Jose Jimenez; Belen Medrano; Pedro Real

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This paper presents a set of tools to compute topological information of simplicial complexes, tools that are applicable to extract topological information from digital pictures. A simplicial complex is encoded in a (non-unique) algebraic-topological format called AM-model. An AM-model for a given object K is determined by a concrete chain homotopy and it provides, in particular, integer (co)homology generators of K and representative (co)cycles of these generators. An algorithm for computing...

Source: http://arxiv.org/abs/1105.3620v2

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Sep 23, 2013
09/13

by
S. E. Woosley

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Most gamma-ray bursts are made during the deaths of massive stars. Here the environmental circumstances, stellar evolutionary paths, and explosion physics that might produce the bursts are reviewed. Neither of the two leading models - collapsar and millisecond magnetar - can be excluded, and both may operate in progenitor stars of different masses, metallicities, and rotation rates. Potential diagnostics are discussed and uncertainties highlighted. Both models are capable of producing a wide...

Source: http://arxiv.org/abs/1105.4193v1

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Sep 23, 2013
09/13

by
Melody L. Massar; Ramamurthy Bhagavatula; Matthew Fickus; Jelena Kovacevic

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The local histogram transform of an image is a data cube that consists of the histograms of the pixel values that lie within a fixed neighborhood of any given pixel location. Such transforms are useful in image processing applications such as classification and segmentation, especially when dealing with textures that can be distinguished by the distributions of their pixel intensities and colors. We, in particular, use them to identify and delineate biological tissues found in histology images...

Source: http://arxiv.org/abs/1105.4069v1

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Sep 23, 2013
09/13

by
David L. Kaplan; Atish Kamble; Marten H. van Kerkwijk; Wynn C. G. Ho

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We present Hubble Space Telescope optical and ultraviolet photometry for five nearby, thermally emitting neutron stars. With these measurements, all seven such objects have confirmed optical and ultraviolet counterparts. Combining our data with archival space-based photometry, we present spectral energy distributions for all sources and measure the "optical excess": the factor by which the measured photometry exceeds that extrapolated from X-ray spectra. We find that the majority have...

Source: http://arxiv.org/abs/1105.4178v1

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Sep 23, 2013
09/13

by
Richard Kenyon; Yuval Peres; Boris Solomyak

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We compute the Hausdorff dimension of the "multiplicative golden mean shift" defined as the set of all reals in $[0,1]$ whose binary expansion $(x_k)$ satisfies $x_k x_{2k}=0$ for all $k\ge 1$, and show that it is smaller than the Minkowski dimension.

Source: http://arxiv.org/abs/1105.3441v2

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Sep 21, 2013
09/13

by
Martin Grohe; Marc Thurley

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Homomorphisms between relational structures are not only fundamental mathematical objects, but are also of great importance in an applied computational context. Indeed, constraint satisfaction problems (CSPs), a wide class of algorithmic problems that occur in many different areas of computer science such as artificial intelligence or database theory, may be viewed as asking for homomorphisms between two relational structures [FedVar98]. In a logical setting, homomorphisms may be viewed as...

Source: http://arxiv.org/abs/1104.0185v3

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Sep 23, 2013
09/13

by
Larry McLerran

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This talk includes a discussion of recent theory developments in the areas related to ultra-relativistic heavy ion collisions. It includes the topics of the Quark Gluon Plasma, Color Glass Condensate, Glasma and Quarkyonic Matter.

Source: http://arxiv.org/abs/1105.4097v1

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Sep 23, 2013
09/13

by
Qi-Liang He; Jing-Bo Xu; Dao-Xin Yao; Ye-Qi Zhang

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We investigate the phenomenon of sudden transition between classical and quantum decoherence in the study of quantum discord for a dissipative cavity QED system, which consists of two noninteracting two-level atoms, each trapped in a dissipative cavity. It is found that the quantum discord between two atoms, which are prepared initially in the X-type quantum states, is not destroyed by the dissipation of the cavities for a finite time interval and the stationary quantum discord can arise in the...

Source: http://arxiv.org/abs/1105.4041v1

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Sep 23, 2013
09/13

by
Lawrence Wiencke; Fernando Arqueros; John Compton; Maria Monasor; David Pilger; Jaime Rosado

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Pulsed UV lasers can provide useful "testbeams" for observatories that use optical detectors, especially fluorescence detectors, to measure high energy cosmic-rays. The light observed by the detector is proportional to the energy of the laser pulse. Since the absolute laser energy can be measured locally, a well-calibrated laser offers a practical way to test the photometric calibration of the cosmic-ray detector including atmospheric corrections. This poster will describe a robotic...

Source: http://arxiv.org/abs/1105.4016v1

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Sep 21, 2013
09/13

by
Liza Huijse; Subir Sachdev

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We give a unified overview of the zero temperature phases of compressible quantum matter: i.e. phases in which the expectation value of a globally conserved U(1) density, Q, varies smoothly as a function of parameters. Provided the global U(1) and translational symmetries are unbroken, such phases are expected to have Fermi surfaces, and the Luttinger theorem relates the volumes enclosed by these Fermi surfaces to . We survey models of interacting bosons and/or fermions and/or gauge fields...

Source: http://arxiv.org/abs/1104.5022v2

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Sep 23, 2013
09/13

by
K. Peña Ramírez; M. R. Zapatero Osorio; V. J. S. Béjar; R. Rebolo; G. Bihain

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(Abridged) We aim to: i) confirm the presence of methane absorption in S Ori 73 (a T-type member candidate of the sig Orionis cluster, 3 Myr, 352 pc) through methane imaging; ii) study S Ori 70 and 73 cluster membership via photometric colors and accurate proper motion analysis; iii) perform a new search to identify additional T-type sig Orionis member candidates with likely masses below 7 Mjup. We obtained HAWK-I (VLT) J, H, and CH4off photometry of an area of 119.15 sq. arcmin in sig Orionis...

Source: http://arxiv.org/abs/1105.4043v1

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Sep 22, 2013
09/13

by
Gideon Maschler

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On a 3-manifold bounding a compact 4-manifold, let a conformal structure be induced from a complete Einstein metric which conformally compactifies to a K\"ahler metric. Formulas are derived for the eta invariant of this conformal structure under additional assumptions. One such assumption is that the K\"ahler metric admits a special K\"ahler-Ricci potential in the sense defined by Derdzinski and Maschler. Another is that the K\"ahler metric is part of an ambitoric structure,...

Source: http://arxiv.org/abs/0805.1646v2

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Sep 19, 2013
09/13

by
Nicolas Bonichon; Jean-François Marckert

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A navigation on a set of points $S$ is a rule for choosing which point to move to from the present point in order to progress toward a specified target. We study some navigations in the plane where $S$ is a non uniform Poisson point process (in a finite domain) with intensity going to $+\infty$. We show the convergence of the traveller path lengths, the number of stages done, and the geometry of the traveller trajectories, uniformly for all starting points and targets, for several navigations...

Source: http://arxiv.org/abs/1009.4679v2

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Sep 23, 2013
09/13

by
Peter Nelson

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For each proper minor-closed subclass $\cM$ of the $\GF(q^2)$-representable matroids containing all simple $\GF(q)$-representable matroids, we give, for all large $r$, a tight upper bound on the number of points in a rank-$r$ matroid in $\cM$, and construct a rank-$r$ matroid in $\cM$ for which equality holds. As a consequence, we give a tight upper bound on the number of points in a $\GF(q^2)$-representable, rank-$r$ matroid with no $\PG(k,q^2)$-minor.

Source: http://arxiv.org/abs/1105.4162v1

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Sep 23, 2013
09/13

by
A. A. Deriglazov; B. F. Rizzuti

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Formalism of extended Lagrangian represent a systematic procedure to look for the local symmetries of a given Lagrangian action. In this work, the formalism is discussed and applied to a field theory. We describe it in detail for a field theory with first-class constraints present in the Hamiltonian formulation. The method is illustrated on examples of electrodynamics, Yang-Mills field and non-linear sigma model.

Source: http://arxiv.org/abs/1105.4171v1

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Sep 23, 2013
09/13

by
A. V. Gopala Rao; K. S. Mallesh; K. N. Srinivasa Rao

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We revisit the problem of the Lorentz transformation of time-separations between events in the Minkowski spacetime to show that there exist a whole class of "time-stretching formulas" which "look" exactly like the well known time-dilation formula (TDF) in special relativity. We highlight the essential di?fferences between the TDF and the similar looking time-stretching formulas in view of the fact that occasionally a time-stretching formula has been mistaken for the TDF in...

Source: http://arxiv.org/abs/1105.4085v1

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Sep 23, 2013
09/13

by
Takashi Kashimura; Shunji Tsuchiya; Yoji Ohashi

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We discuss an idea to realize a spontaneous current in a superfluid Fermi gas. When a polarized Fermi superfluid ($N_\up > N_\dwn$, where $N_\sigma$ is the number of atoms in the hyperfine state described by pseudospin $\sigma=\uparrow, \downarrow$.) is loaded onto a ring-shaped trap with a weak potential barrier, some of excess atoms ($\Delta N=N_\uparrow-N_\downarrow$) are localized around the barrier. As shown in our previous paper [T. Kashimura, S. Tsuchiya, and Y. Ohashi, Phys. Rev. A...

Source: http://arxiv.org/abs/1105.4023v1

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Sep 23, 2013
09/13

by
Dorje C. Brody; Eva-Maria Graefe

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The dynamical aspects of a spin-1/2 particle in Hermitian coquaternionic quantum theory is investigated. It is shown that the time evolution exhibits three different characteristics, depending on the values of the parameters of the Hamiltonian. When energy eigenvalues are real, the evolution is either isomorphic to that of a complex Hermitian theory on a spherical state space, or else it remains unitary along an open orbit on a hyperbolic state space. When energy eigenvalues form a complex...

Source: http://arxiv.org/abs/1105.4038v1

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Sep 23, 2013
09/13

by
Wayne M. Schlingman; Yancy L. Shirley; David E. Bolin; Erik Rosolowsky; John Bally; Cara Battersby; Miranda K. Dunham; Timothy P. Ellsworth-Bowers; Neal J. Evans II; Adam Ginsburg; Guy Stringfellow

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We present the results of observations of 1882 sources in the Bolocam Galactic Plane Survey (BGPS) at 1.1 mm with the 10m Heinrich Hertz Telescope simultaneously in HCO+ J=3-2 and N2H+ J=3-2. We detect 77% of these sources in HCO^+ and 51% in N2H+ at greater than 3$\sigma$. We find a strong correlation between the integrated intensity of both dense gas tracers and the 1.1 mm dust emission of BGPS sources. We determine kinematic distances for 529 sources (440 in the first quadrant breaking the...

Source: http://arxiv.org/abs/1105.4181v1

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46

Sep 23, 2013
09/13

by
M. Szymczak; P. Wolak; A. Bartkiewicz; H. J. van Langevelde

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We report the discovery of periodic flares of 6.7GHz methanol maser in the young massive stellar object G22.357+0.066. The target was monitored in the methanol maser line over 20 months with the Torun 32m telescope. The emission was also mapped at two epochs using the EVN. The 6.7GHz methanol maser shows periodic variations with a period of 179 days. The periodic behavior is stable for the last three densely sampled cycles and has even been stable over ~12 years, as the archival data suggest....

Source: http://arxiv.org/abs/1105.4089v1

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Sep 23, 2013
09/13

by
Jakob Heide Jørgensen; Tobias Lindstrøm Jensen; Per Christian Hansen; Søren Holdt Jensen; Emil Y. Sidky; Xiaochuan Pan

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Total-variation (TV)-based Computed Tomography (CT) image reconstruction has shown experimentally to be capable of producing accurate reconstructions from sparse-view data. In particular TV-based reconstruction is very well suited for images with piecewise nearly constant regions. Computationally, however, TV-based reconstruction is much more demanding, especially for 3D imaging, and the reconstruction from clinical data sets is far from being close to real-time. This is undesirable from a...

Source: http://arxiv.org/abs/1105.4002v1

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29

Sep 18, 2013
09/13

by
Alberto Guijosa; Juan F. Pedraza

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We carry out an analytic study of the early-time motion of a quark in a strongly-coupled maximally-supersymmetric Yang-Mills plasma, using the AdS/CFT correspondence. Our approach extracts the first thermal effects as a small perturbation of the known quark dynamics in vacuum, using a double expansion that is valid for early times and for (moderately) ultrarelativistic quark velocities. The quark is found to lose energy at a rate that differs significantly from the previously derived...

Source: http://arxiv.org/abs/1102.4893v2

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Sep 18, 2013
09/13

by
Daniel B. Larremore; Woodrow L. Shew; Edward Ott; Juan G. Restrepo

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We study the effects of network topology on the response of networks of coupled discrete excitable systems to an external stochastic stimulus. We extend recent results that characterize the response in terms of spectral properties of the adjacency matrix by allowing distributions in the transmission delays and in the number of refractory states, and by developing a nonperturbative approximation to the steady state network response. We confirm our theoretical results with numerical simulations....

Source: http://arxiv.org/abs/1102.2934v2