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Formation of compressed flat electron beams with high transverse-emittance ratios
http://inspirehep.net/record/1311911
FERMILAB-PUB-14-103-AD-APC<br />Phys.Rev.ST Accel.Beams 17 (2014) 084401<br /><br />by: Zhu, J. (Fermilab) et al.<br /><br /><strong>Abstract:</strong> <br />Flat beams—beams with asymmetric transverse emittances—have important applications in novel light-source concepts and advanced-acceleration schemes and could possibly alleviate the need for damping rings in lepton colliders. Over the last decade, a flat beam generation technique based on the conversion of an angular-momentum-dominated beam was proposed and experimentally tested. In this paper we explore the production of compressed flat beams. We especially investigate and optimize the flat beam transformation for beams with substantial fractional energy spread. We use as a simulation example the photoinjector of Fermilab’s Advanced Superconducting Test Accelerator. The optimizations of the flat beam generation and compression at Advanced Superconducting Test Accelerator were done via start-to-end numerical simulations for bunch charges of 3.2 nC, 1.0 nC, and 20 pC at ∼37 MeV. The optimized emittances of flat beams with different bunch charges were found to be 0.25 μm (emittance ratio is ∼400), 0.13 μm, 15 nm before compression, and 0.41 μm, 0.20 μm, 16 nm after full compression, respectively, with peak currents as high as 5.5 kA for a 3.2−nC flat beam. These parameters are consistent with requirements needed to excite wakefields in asymmetric dielectric-lined waveguides or produce significant photon flux using small-gap micro-undulators.Piot, P.Fri, 22 Aug 2014 15:24:00 GMThttp://inspirehep.net/record/1311911The D0 Experiment at Fermilab: Collected Physics Papers: Reprints from Physical Review Letters and Physical Review D
http://inspirehep.net/record/1311910
FERMILAB-PUB-09-228-E<br />Fri, 22 Aug 2014 15:15:32 GMThttp://inspirehep.net/record/1311910Computer assisted proofs
http://inspirehep.net/record/1311907
<br />by: Lanford III, O.E. (Zurich, ETH D-MATH)<br />Lanford III, O.E.Fri, 22 Aug 2014 14:34:12 GMThttp://inspirehep.net/record/1311907A stochastic primer
http://inspirehep.net/record/1311905
<br />by: Klauder, J.R. (Florida U.)<br />Klauder, J.R.Fri, 22 Aug 2014 14:27:52 GMThttp://inspirehep.net/record/1311905The Lotka-Volterra model as a Hamiltonian system
http://inspirehep.net/record/1311904
HU-TFT-93-66<br /><br />by: Cronström, C. (Helsinki U.) et al.<br />Cronström, C.Fri, 22 Aug 2014 14:23:43 GMThttp://inspirehep.net/record/1311904Conformal aspects of quantum field theory and their applications to realistic physics
http://inspirehep.net/record/1311898
<br />by: Mølgaard, Esben (Southern Denmark U., CP3-Origins)<br /><br /><strong>Abstract:</strong> <br />In this thesis, we will present the results of our studies into the nature of four–dimensional, non-supersymmetric quantum field theory, particularly that of renormalization group flows. This is of course a vast subject and we could not hope to cover it all. We begin our presentation by discussing two rather different models that we will return to several times during the course of the thesis. The first is the standard model of particle physics, where we put a great emphasis on the Higgs field and its particle, the second is an SU(Nc) toy model which has been found to have many interesting properties. We then proceed to introduce the concept of renormalization, and dedicate an extended section to a new method that we have developed for the calculation of (especially) beta functions. We also take time to discuss fixed points in gauge theories, and how the presence or absence of these is determined by the parameters of the theory in question. Next, we study the conjectured a theorem, i.e., the proposal that there exists a function a of the couplings in a four-dimensional quantum field theory which is monotonic along any renormalization group flow. We test the weak form of this conjecture, which states that a is larger at UV fixed points than at IR fixed points, and find that this holds in the toy model even when none of the fixed points is Gaussian. From our investigations into the a theorem, we discovered that to preserve the symmetries of a gauge-Yukawa theory, it is necessary to run the gauge couplings with a beta function that is calculated to one higher loop order than the Yukawa beta functions, which must in turn be computed to one higher loop order than the quartic beta functions. We use this very important result to refine computations done previously by others regarding the stability of the standard model vacuum. Finally, we consider the renormalization group flows of a model inspired by the standard model lepton sector when the beta functions are computed to different loop orders. We use this to give quantitative statements regarding the trustworthiness of perturbation theory.Mølgaard, EsbenFri, 22 Aug 2014 12:03:56 GMThttp://inspirehep.net/record/1311898LHC Phenomenology and Neutrino Physics in GUT inspired SUSY
http://inspirehep.net/record/1311897
<br />by: Reichert, Laslo Alexander (Valencia U.)<br /><br /><strong>Abstract:</strong> <br />Motivated by current neutrino data we calculate in the first part of this thesis supersymmetric mass spectra within three variants of the seesaw mechanism, com monly known as type-I, type-II and type-III seesaw, using full 2-loop RGEs and minimal Supergrav ity boundary conditions. The type-II seesaw is realized using one pair of 15 and ̄ 15 superfields, while the type-III is realized using three copies of 24 M superfields. The 15, ̄ 15 and 24 M multipet are representations of a SU (5) gauge group. Using published, estimated errors on SUSY mass observable s attainable at the LHC and in a combined LHC+ILC analysis, we calculate expected errors for t he parameters of the models, most notably the seesaw scale. Since our conclusions crucially de pend on the reliability of the theoretically forecasted error bars, we discuss in some detail the accuracies wh ich need to be achieved for the most important LHC and ILC observables before an analysis, such as the one presented here, can find any hints for seesaw mechanism in SUSY spectra. The second part of this thesis is motivated by the discovery of the new boson at around 125 GeV at the LHC. To circumvent the upper limit on the Higgs mass in the MSSM the minimal supersymmetric U (1) B − L × U (1) R extension of the standard model is discussed. Gauge couplings unify as in the MSSM, eve n if the scale of U (1) B − L × U (1) R breaking is as low as order TeV and the model can be embedded into an SO (10) grand unified theory. The phenomenology of the model differs in some important a spects from the MSSM, leading potentially to rich phenomenology at the LHC. It predicts more l ight Higgs states and the mostly left CP-even Higgs has a mass reaching easily 125 GeV, with no co nstraints on the SUSY spectrum. Right sneutrinos can be the lightest supersymmetric particle, c hanging all dark matter constraints on SUSY parameter space. The model has seven neutralinos and sq uark/gluino decay chains involve more complicated cascades than in the MSSM. We also discuss bri efly low-energy and accelerator constraints on the model, where the most important limits come f rom recent Z’ searches at the LHC and upper limits on lepton flavour violation.Reichert, Laslo AlexanderFri, 22 Aug 2014 11:54:31 GMThttp://inspirehep.net/record/1311897Proceedings, International Conference on IC Design & Technology (ICICDT 2013): Pavia, Italy, May 29-31, 2013
http://inspirehep.net/record/1311896
<br />by: Ea, ThomasEa, ThomasFri, 22 Aug 2014 11:25:12 GMThttp://inspirehep.net/record/1311896urn:ISBN:9781467347402urn:ISBN:9781467347419IEEE2013Proceedings, IEEE International Instrumentation and Measurement Technology Conference (I2MTC 2014): Montevideo, Uruguay, May 12-15, 2014
http://inspirehep.net/record/1311895
<br />by: Miguez, Juan CarlosMiguez, Juan CarlosFri, 22 Aug 2014 11:07:32 GMThttp://inspirehep.net/record/1311895urn:ISBN:9781467363853IEEE2014Aspectos da Torção nas Teorias Quânticas da Gravidade
http://inspirehep.net/record/1311894
<br />by: Nardi, Rafael (Rio de Janeiro, CBPF)<br /><br /><strong>Abstract:</strong> <br />Studies of the gravitational behaviour at the microscale points towards a very important role played by torsion in caracterizing dynamics of gravitation. This is suggested by both Loop Quantum Gravity and Superstring Theory, the two main candidates to give a consistent description of Nature in this scale. In these fundamental scenarios, gravity is regarded as a gauge theory following the proposal by Utyama/Kibble/Sciama (1955). In this work, we develop a new basis of spin-projectors in the space spanned by rank-3 Lorentz tensors that may be useful in determining the dynamics of gravitational theories with torsion at the tree approximation, in terms of its fundamental local excitations. Also, we apply our set-up to a specific problem, inspired by low-energy effective string theories.Nardi, RafaelFri, 22 Aug 2014 09:46:54 GMThttp://inspirehep.net/record/1311894Astrosociology: Interwiews about an infinite universe
http://inspirehep.net/record/1311893
physics.hist-pharXiv:1408.4795<br /><br />by: Høg, Erik<br /><strong>Abstract:</strong> <br />If the universe is infinite now it has always been infinite. This is the opinion of many astronomers today as can be concluded from the following series of interviews, but the opinions differ much more than I had expected. Many astronomers do not have a clear opinion on this matter. Others have a clear opinion, but very different from the majority. Detailed arguments by two experts on general relativity are also included. Observations show that the universe is flat, i.e. the curvature is zero within the small uncertainty of measurements. This implies an infinite universe, though most probably we will never know that for certain. For comparison with the recent interviews, opinions during the past 2300 years since Aristotle about the universe being finite or infinite have been collected from literature, and it appears that the scientists often had quite definite opinions. \c{opyright} Anita Publications. All rights reserved.Høg, ErikFri, 22 Aug 2014 08:07:02 GMThttp://inspirehep.net/record/1311893Deficient Reasoning for Dark Matter in Galaxies
http://inspirehep.net/record/1311892
astro-ph.GAarXiv:1408.5054<br /><br />by: Feng, James Q.<br /><strong>Abstract:</strong> <br />Astronomers have been using the measured luminosity to estimate the {\em luminous mass} of stars, based on empirically established mass-to-light ratio which seems to be only applicable to a special class of stars---the main-sequence stars---with still considerable uncertainties. Another basic tool to determine the mass of a system of stars or galaxies comes from the study of their motion, as Newton demonstrated with his law of gravitation, which yields the {\em gravitational mass}. Because the luminous mass can at best only represent a portion of the gravitational mass, finding the luminous mass to be different or less than the gravitational mass should not be surprising. Using such an apparent discrepancy as a compelling evidence for the so-called dark matter, which has been believed to possess mysterious nonbaryonic properties and present a dominant amount in galaxies and the universe, seems to be too far a stretch when seriously examining the facts and uncertainties in the measurement techniques. In our opinion, a galaxy with star type distribution varying from its center to edge may have a mass-to-light ratio varying accordingly. With the thin-disk model computations based on measured rotation curves, we found that most galaxies have a typical mass density profile that peaks at the galactic center and decreases rapidly within $\sim 5\%$ of the cut-off radius, and then declines nearly exponentially toward the edge. The predicted mass density in the Galactic disk is reasonably within the reported range of that observed in interstellar medium. This leads us to believe that ordinary baryonic matter can be sufficient for supporting the observed galactic rotation curves; speculation of large amount of non-baryonic matter may be based on an ill-conceived discrepancy between gravitational mass and luminous mass which appears to be unjustified.Feng, James Q.Fri, 22 Aug 2014 08:06:53 GMThttp://inspirehep.net/record/1311892Tidal evolution of disky dwarf galaxies: prograde versus retrograde orbits
http://inspirehep.net/record/1311891
astro-ph.GAarXiv:1408.4973<br /><br />by: Lokas, Ewa L.<br /><strong>Abstract:</strong> <br />The formation of dwarf spheroidal galaxies in the Local Group from disky progenitors via tidal interaction with a bigger host is one of the most promising scenarios of their origin. Using N-body simulations we study the process by following the evolution of a disky dwarf orbiting a Milky Way-like host. We focus on the effect of the orientation of the dwarf galaxy disk's angular momentum with respect to the orbital one. We find a strong dependence of the efficiency of the transformation from a disk to a spheroid on the disk orientation. The effect is strongest for the exactly prograde and weakest for the exactly retrograde orbit. In the prograde case the stellar component forms a strong bar and remains prolate until the end of the evolution, while its rotation is very quickly replaced by random motions of the stars. In the retrograde case the dwarf remains oblate, does not form a bar and loses rotation very slowly. Our results suggest that resonant effects are the most important mechanism underlying the evolution while tidal shocking plays only a minor role.Lokas, Ewa L.Fri, 22 Aug 2014 08:06:42 GMThttp://inspirehep.net/record/1311891Puzzling Outer-Density Profile of the Dark Matter Halo in the Andromeda Galaxy
http://inspirehep.net/record/1311890
astro-ph.GAarXiv:1408.4920<br /><br />by: Kirihara, Takanobu<br /><strong>Abstract:</strong> <br />The cold dark matter (CDM) cosmology, which is the standard theory of the structure formation in the universe, predicts that the outer density profile of dark matter halos decreases with the cube of distance from the center. However, so far not much effort has examined this hypothesis. Large-scale stellar structures detected by the recent observations in the halo of the Andromeda galaxy (M31) provide an attractive window to explore the structure of the dark matter halo. Using an N-body simulation of the interaction between an accreting satellite galaxy and M31, we investigate the mass-density profile of the dark matter halo in M31. To reproduce the Andromeda Giant Southern Stream and the stellar shells at the east and west sides of M31, we find the sufficient condition for the power-law index $\alpha$ of the outer density distribution of the dark matter halo. The best-fit parameter is $\alpha=-3.7$, which is steeper than the CDM prediction.Kirihara, TakanobuFri, 22 Aug 2014 08:06:33 GMThttp://inspirehep.net/record/1311890The quantum hydrodynamic formulation of Dirac equation and its generalized stochastic and non-linear analogs
http://inspirehep.net/record/1311888
quant-pharXiv:1406.0595<br /><br />by: Chiarelli, Piero<br /><strong>Abstract:</strong> <br />The quantum hydrodynamic like equations as a function of two real sets of variables, the 4x4 action matrix and the 4 dimensional wave function modulus vector of the Dirac equation, are derived in the present work. The paper shows that in the low velocity limit the equations lead to the hydrodynamic representation of the Pauli equation for charged particle with spin given by Janossy and by Bialynicki.The Lorentz invariance of the relativistic quantum potential that generates the non-local behavior of the quantum mechanics is discussed.Chiarelli, PieroFri, 22 Aug 2014 05:52:58 GMThttp://inspirehep.net/record/1311888Exploring quantum phases by driven dissipation
http://inspirehep.net/record/1311887
quant-pharXiv:1408.4616<br /><br />by: Lang, Nicolai<br /><strong>Abstract:</strong> <br />Ever since the insight spreaded that tailored dissipation can be employed to control quantum systems and drive them towards pure states, the field of non-equilibrium quantum mechanics gained remarkable momentum. So far research focussed on emergent phenomena caused by the interplay and competition of unitary Hamiltonian and dissipative Markovian dynamics. In this manuscript we zero in on a so far rather understudied aspect of open quantum systems and non-equilibrium physics, namely the utilization of purely dissipative couplings to explore pure quantum phases and non-equilibrium phase transitions. To illustrate this concept, we introduce and scrutinize purely dissipative counterparts of (1) the paradigmatic transverse field Ising model and (2) the considerably more complex $\mathbb{Z}_2$ lattice gauge theory with coupled matter field. We show that, in mean field approximation, the non-equilibrium phase diagrams parallel the (thermal) phase diagrams of the Hamiltonian "blue print" theories qualitatively.Lang, NicolaiFri, 22 Aug 2014 05:52:49 GMThttp://inspirehep.net/record/1311887Open Systems Dynamics for Propagating Quantum Fields
http://inspirehep.net/record/1311886
quant-pharXiv:1408.4447<br /><br />by: Baragiola, Ben Q.<br /><strong>Abstract:</strong> <br />In this dissertation, I explore interactions between matter and propagating light. The electromagnetic field is modeled as a reservoir of quantum harmonic oscillators successively streaming past a quantum system. Each weak and fleeting interaction entangles the light and the system, and the light continues its course. Within the framework of open quantum systems, the light is eventually traced out, leaving the reduced quantum state of the system as the primary mathematical subject. Two major results are presented. The first is a master equation approach for a quantum system interacting with a traveling wave packet prepared with a definite number of photons. In contrast to quasi-classical states, such as coherent or thermal fields, these N-photon states possess temporal mode entanglement, and local interactions in time have nonlocal consequences. The second is a model for a three-dimensional light-matter interface for an atomic ensemble interacting with a paraxial laser beam and its application to the generation of QND spin squeezing. Both coherent and incoherent dynamics due to spatially inhomogeneous atom-light coupling across the ensemble are accounted for. Measurement of paraxially scattered light can generate squeezing of an atomic spin wave, while diffusely scattered photons lead to spatially local decoherence.Baragiola, Ben Q.Fri, 22 Aug 2014 05:52:40 GMThttp://inspirehep.net/record/1311886Connectivity of Higgs bundle moduli for complex reductive Lie groups
http://inspirehep.net/record/1311885
math.AGarXiv:1408.4778<br /><br />by: García-Prada, Oscar<br /><strong>Abstract:</strong> <br />We carry an intrinsic approach to the study of the connectivity of the moduli space M_G of G-Higgs bundles, over a compact Riemann surface, when G is a complex reductive (not necessarily connected) Lie group. We prove that the number of connected components of M_G is indexed by the corresponding topological invariants. In particular, this gives an alternative proof of the counting by J. Li of the number of connected components of the moduli space of flat G-connections in the case in which G is connected and semisimple.García-Prada, OscarFri, 22 Aug 2014 05:52:28 GMThttp://inspirehep.net/record/1311885Symplectic structures on $3$-Lie algebras
http://inspirehep.net/record/1311884
math.RTarXiv:1408.4763<br /><br />by: Bai, Ruipu<br /><strong>Abstract:</strong> <br />The symplectic structures on $3$-Lie algebras and metric symplectic $3$-Lie algebras are studied. For arbitrary $3$-Lie algebra $L$, infinite many metric symplectic $3$-Lie algebras are constructed. It is proved that a metric $3$-Lie algebra $(A, B)$ is a metric symplectic $3$-Lie algebra if and only if there exists an invertible derivation $D$ such that $D\in Der_B(A)$, and is also proved that every metric symplectic $3$-Lie algebra $(\tilde{A}, \tilde{B}, \tilde{\omega})$ is a $T^*_{\theta}$-extension of a metric symplectic $3$-Lie algebra $(A, B, \omega)$. Finally, we construct a metric symplectic double extension of a metric symplectic $3$-Lie algebra by means of a special derivation.Bai, RuipuFri, 22 Aug 2014 05:52:18 GMThttp://inspirehep.net/record/1311884Quantum Integrability and Generalised Quantum Schubert Calculus
http://inspirehep.net/record/1311883
math.RTarXiv:1408.4718<br /><br />by: Gorbounov, Vassily<br /><strong>Abstract:</strong> <br />A groundbreaking connection between generalised cohomology theories and quantum groups was suggested in a paper by Ginzburg, Kapranov, and Vasserot about twenty years ago. The authors argued that the major examples of generalised cohomology theories, namely, ordinary cohomology, K-theory and elliptic cohomology, associated with the additive, the multiplicative and the elliptic formal group law should be related to the rational, the trigonometric, and the elliptic solutions of the celebrated Yang-Baxter equation and therefore to the appropriate quantum groups. At the time there were not too many examples to support this claim, but recently Nekrasov, Shatashvili, and Braverman, Maulik, Okounkov related the quantum equivariant cohomology and quantum equivariant K-theory of Nakajima varieties in concrete terms with quantum integrable systems and quantum groups. In this article we present a different instance of such a relation by linking the structure of quantum integrable systems related to the asymmetric six-vertex model with the quantum equivariant cohomology and quantum equivariant K-theory of Grassmannians. We start with a one parameter family of multiplicative formal group laws and use them to extend the definition of the integrable systems called vicious and osculating walkers. We solve these models explicitly, that is we compute the spectrum of the so-called Bethe algebra generated by their commuting transfer matrices. Specialising the parameter such that the formal group law becomes additive,we identify the Bethe algebra as the quantum equivariant cohomology of the Grassmannians, while for the formal group law of K-theory we obtain a conjectural description of the equivariant quantum K-theory of the Grassmannians which reduces to the known results for (non-equivariant) quantum K-theory by Buch and Mihalcea and (non-quantum) equivariant K-theory by Kostant and Kumar.Gorbounov, VassilyFri, 22 Aug 2014 05:52:09 GMThttp://inspirehep.net/record/1311883A non-commutative analogue of the Odlyzko bounds and bounds on performance for space-time lattice codes
http://inspirehep.net/record/1311882
cs.ITarXiv:1408.4630<br /><br />by: Linowitz, Benjamin<br /><strong>Abstract:</strong> <br />This paper considers space-time coding over several independently Rayleigh faded blocks. In particular we will concentrate on giving upper bounds for the coding gain of lattice space-time codes as the number of blocks grow. This problem was previously considered in the single antenna case by Bayer et al. in 2006. Crucial to their work was Odlyzko's bound on the discriminant of an algebraic number field, as this provides an upper bound for the normalized coding gain of number field codes. In the MIMO context natural codes are constructed from division algebras defined over number fields and the coding gain is measured by the discriminant of the corresponding (non-commutative) algebra. In this paper we will develop analogues of the Odlyzko bounds in this context and show how these bounds limit the normalized coding gain of a very general family of division algebra based space-time codes. These bounds can also be used as benchmarks in practical code design and as tools to analyze asymptotic bounds of performance as the number of independently faded blocks increases.Linowitz, BenjaminFri, 22 Aug 2014 05:51:58 GMThttp://inspirehep.net/record/1311882Proceedings, International Conference on Flavor Physics and Mass Generation: Singapore, Singapore, February 10-14, 2014
http://inspirehep.net/record/1311881
Int.J.Mod.Phys. A29 (2014)<br /><br />by: Fritzsch, HaraldFritzsch, HaraldFri, 22 Aug 2014 05:51:55 GMThttp://inspirehep.net/record/1311881Octavic theta series
http://inspirehep.net/record/1311880
math.AGarXiv:1408.4537<br /><br />by: Freitag, Eberhard<br /><strong>Abstract:</strong> <br />Let L be the even unimodular lattice of signature (2,10), In the paper [FS] we considered the subgroup O(L)^+ of index two in the orthogonal group. It acts biholomorphically on a ten dimensional tube domain H_{10}. We found a 715 dimensional space of modular forms with respect to the principal congruence subgroup of level two O^+(L)[2]. It defines an everywhere regular birational embedding of the related modular variety into the 714 dimensional projective space. In this paper, we prove that this space of orthogonal modular forms is related to a space of theta series. The main tool is a modular embedding of H_{10} into the Siegel half space of degree 16. As a consequence the modular forms in the 715 dimensional space can be obtained as restrictions of the simplest among all theta series.Freitag, EberhardFri, 22 Aug 2014 05:51:47 GMThttp://inspirehep.net/record/1311880The Moutard transformation of two-dimensional Dirac operators and the Mobius geometry
http://inspirehep.net/record/1311879
math.DGarXiv:1408.4464<br /><br />by: Taimanov, Iskander A.<br /><strong>Abstract:</strong> <br />We describe the action of the (Mobius) inversion on the data of the Weierstrass representation of surfaces in the three-space and show that the Moutard transformation of two-dimensional Dirac operators has a geometrical meaning: it maps the potential $U$ of a surface $S$ into the potential of its inversion.Taimanov, Iskander A.Fri, 22 Aug 2014 05:51:35 GMThttp://inspirehep.net/record/1311879Ultrastable low-noise current amplifier
http://inspirehep.net/record/1311878
physics.ins-detarXiv:1408.5088<br /><br />by: Drung, Dietmar<br /><strong>Abstract:</strong> <br />An ultrastable low-noise current amplifier (ULCA) is presented. The ULCA is a non-cryogenic instrument based on specially designed operational amplifiers and resistor networks. It involves two stages, the first providing a 1000-fold current gain and the second performing a current-to-voltage conversion via an internal 1 MOhm reference resistor or, optionally, an external standard resistor. The ULCA's transfer coefficient is extremely stable versus time, temperature and current amplitude within the full dynamic range of +/-5 nA. A low noise level of 2.4 fA/sqrt(Hz) helps to keep averaging times low at small input currents. A cryogenic current comparator is used to calibrate both input current gain and output transresistance, providing traceability to the quantum Hall effect. Typically, within one day after calibration, the uncertainty contribution from short-term fluctuations of the transresistance is below one part in 10^7. The long-term stability is expected to be better than one part in 10^5 over a year. A high-precision variant is available that shows a substantially improved stability at the expense of a higher noise level of 7.5 fA/sqrt(Hz). The ULCA also allows the traceable generation of small electrical currents or the calibration of high-ohmic resistors.Drung, DietmarFri, 22 Aug 2014 04:43:51 GMThttp://inspirehep.net/record/1311878