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Manuel C.,Institute Ciencias Del Espacio IEEC CSIC | Soto J.,University of Barcelona | Stetina S.,University of Washington
EPJ Web of Conferences | Year: 2017

We show that effective field theory techniques can be applied in the high temperature T regime of plasmas to improve the accuracy of the physics of the hard scales (or scales of order T), and as a by-product, also that of the soft scales (or scales of order gT). At leading order in the coupling constant the hard scales of the plasma can be viewed as on-shell classical particles. Based on this observation, and without any reference to the state of the system, we derive an effective field theory describing the quantum fluctuations around an on-shell fermion with energy p, described as a set of high dimension operators over the on-shell energy p. When applied to systems close to thermal equilibrium, where for most on-shell particles p ∼ T, we show that the on-shell effective field theory (OSEFT) properly describes the HTL photon polarization tensor of QED, and its 1/T corrections. For the soft scales the first non-vanishing power correction turns out to be a perturbative correction to the HTL result. © The Authors, published by EDP Sciences, 2017.

Torres-Rincon J.M.,CNRS Laboratory of Subatomic Physics and Associated Technologies | Abreu L.M.,Federal University of Bahia | Cabrera D.,Goethe University Frankfurt | Romanets O.,University of Groningen | And 2 more authors.
Journal of Physics: Conference Series | Year: 2016

We review the recent results of heavy meson diffusion in thermal hadronic matter. The interactions of D and B mesons with other hadrons (light mesons and baryons) are extracted from effective field theories based on chiral and heavy-quark symmetries. When these guiding principles are combined with exact unitarity, physical values of the cross sections are obtained. These cross sections (which contain resonant contributions) are used to calculate the drag and diffusion coefficients of heavy mesons immersed in a thermal and dense medium. The transport coefficients are computed using a Fokker-Planck reduction of the Boltzmann equation.

Watts A.L.,University of Amsterdam | Andersson N.,University of Southampton | Chakrabarty D.,Massachusetts Institute of Technology | Feroci M.,Istituto di Astrofisica Spaziale e Fisica Cosmica | And 18 more authors.
Reviews of Modern Physics | Year: 2016

One of the primary science goals of the next generation of hard x-ray timing instruments is to determine the equation of state of matter at supranuclear densities inside neutron stars by measuring the radius of neutron stars with different masses to accuracies of a few percent. Three main techniques can be used to achieve this goal. The first involves waveform modeling. The flux observed from a hotspot on the neutron star surface offset from the rotational pole will be modulated by the star's rotation, and this periodic modulation at the spin frequency is called a pulsation. As the photons propagate through the curved spacetime of the star, information about mass and radius is encoded into the shape of the waveform (pulse profile) via special and general-relativistic effects. Using pulsations from known sources (which have hotspots that develop either during thermonuclear bursts or due to channeled accretion) it is possible to obtain tight constraints on mass and radius. The second technique involves characterizing the spin distribution of accreting neutron stars. A large collecting area enables highly sensitive searches for weak or intermittent pulsations (which yield spin) from the many accreting neutron stars whose spin rates are not yet known. The most rapidly rotating stars provide a clean constraint, since the limiting spin rate where the equatorial surface velocity is comparable to the local orbital velocity, at which mass shedding occurs, is a function of mass and radius. However, the overall spin distribution also provides a guide to the torque mechanisms in operation and the moment of inertia, both of which can depend sensitively on dense matter physics. The third technique is to search for quasiperiodic oscillations in x-ray flux associated with global seismic vibrations of magnetars (the most highly magnetized neutron stars), triggered by magnetic explosions. The vibrational frequencies depend on stellar parameters including the dense matter equation of state, and large-area x-ray timing instruments would provide much improved detection capability. An illustration is given of how these complementary x-ray timing techniques can be used to constrain the dense matter equation of state and the results that might be expected from a 10 m2 instrument are discussed. Also discussed are how the results from such a facility would compare to other astronomical investigations of neutron star properties. © 2016 American Physical Society.

Norberg P.,University of Edinburgh | Gaztanaga E.,Institute Ciencias del Espacio IEEC CSIC | Baugh C.M.,Durham University | Croton D.J.,Swinburne University of Technology
Monthly Notices of the Royal Astronomical Society | Year: 2011

For galaxy clustering to provide robust constraints on cosmological parameters and galaxy formation models, it is essential to make reliable estimates of the errors on clustering measurements. We present a new technique, based on a spatial jackknife (JK) resampling, which provides an objective way to estimate errors on clustering statistics. Our approach allows us to set the appropriate size for the JK subsamples. The method also provides a means to assess the impact of individual regions on the measured clustering, and thereby to establish whether or not a given galaxy catalogue is dominated by one or several large structures, preventing it to be considered as a 'fair sample'. We apply this methodology to the two- and three-point correlation functions measured from a volume-limited sample of M* galaxies drawn from Data Release 7 of the Sloan Digital Sky Survey (SDSS). The frequency of JK subsample outliers in the data is shown to be consistent with that seen in large N-body simulations of clustering in the cosmological constant plus cold dark matter cosmology. We also present a comparison of the three-point correlation function in SDSS and Two-degree-Field Galaxy Redshift Survey using this approach and find consistent measurements between the two samples. © 2011 The Authors. Monthly Notices of the Royal Astronomical Society © 2011 RAS.

Cabre A.,University of Pennsylvania | Gaztanaga E.,Institute Ciencias del Espacio IEEC CSIC
Monthly Notices of the Royal Astronomical Society: Letters | Year: 2011

Recent publications claim that there is no convincing evidence for measurements of the baryonic acoustic oscillation (BAO) feature in galaxy samples using either monopole or radial information. Different claims seem contradictory: data are either not consistent with the BAO model or data are consistent with both the BAO model and featureless models without BAO. We investigate this point with a set of 216 realistic mock galaxy catalogues extracted from MICE 7680, one of the largest volume dark matter simulation run to date, with a volume of 1300 cubical gigaparsecs. Our mocks cover similar volume, densities and bias as the real galaxies and provide 216 realizations of the lambda or ω = -1 cold dark matter (ωCDM) BAO model. We find that only 20 per cent of the mocks show a statistically significant (3σ) preference for the true (input) ωCDM BAO model as compared to a featureless (non-physical) model without BAO. Thus the volume of current galaxy samples is not yet large enough to claim that the BAO feature has been detected. Does this mean that we cannot locate the BAO position? Using a simple (non-optimal) algorithm we show that in 50 per cent (100 per cent) of the mocks, we can find the BAO position within 5 per cent (20 per cent) of the true value. These two findings are not in contradiction: the former is about model selection and the later is about parameter fitting within a model. We conclude that current monopole and radial BAO measurements can be used as standard rulers if we assume ωCDM type of models. © 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS.

Yamagata-Sekihara J.,Japan National Institute of Advanced Industrial Science and Technology | Garcia-Recio C.,University of Granada | Nieves J.,Institute Fisica Corpuscular centro mixto CSIC UV | Salcedo L.L.,University of Granada | And 2 more authors.
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2016

We investigate the structure and formation of charmed meson-nucleus systems, with the aim of understanding the charmed meson-nucleon interactions and the properties of the charmed mesons in the nuclear medium. The D- mesic nuclei are of special interest, since they have tiny decay widths due to the absence of strong decays for the D-N pair. Employing an effective model for the D-N and DN interactions and solving the Klein-Gordon equation for D- and D in finite nuclei, we find that the D--11B system has 1s and 2p mesic nuclear states and that the D0-11B system binds in a 1s state. In view of the forthcoming experiments by the PANDA and CBM Collaborations at the future FAIR facility and the J-PARC upgrade, we calculate the formation spectra of the [D--11B] and [D0-11B] mesic nuclei for an antiproton beam on a 12C target. Our results suggest that it is possible to observe the 2p D- mesic nuclear state with an appropriate experimental setup. © 2016 The Authors.

Crocce M.,Institute Ciencias del Espacio IEEC CSIC | Gaztanaga E.,Institute Ciencias del Espacio IEEC CSIC | Cabre A.,University of Pennsylvania | Carnero A.,CIEMAT | Sanchez E.,CIEMAT
Monthly Notices of the Royal Astronomical Society | Year: 2011

The possibility of measuring redshift-space distortions (RSDs) using photometric data has been recently highlighted. This effect complements and significantly alters the detectability of baryon acoustic oscillations (BAO) in photometric surveys. In this paper we present measurements of the angular correlation function of luminous red galaxies (LRGs) in the photometric catalogue of the final data release [data release 7 (DR7)] of the Sloan Digital Sky Survey II (SDSS-II). The sample compromises ~1.5 × 106 LRGs distributed in 0.45 < z < 0.65, with a characteristic photometric error of ~0.05. Our measured correlation centred at z= 0.55 is in very good agreement with predictions from standard Λcold dark matter (ΛCDM) in a broad range of angular scales, 05 < θ < 6°. We find that the growth of structure can indeed be robustly measured, with errors matching expectations. The velocity growth rate is recovered as fσ8= 0.53 ± 0.42 when no prior is imposed on the growth factor and the background geometry follows a ΛCDM model with 7-year Wilkinson Microwave Anisotropy Probe (WMAP7)+SNIa priors. This is compatible with the corresponding General Relativity (GR) prediction fσ8= 0.45 for our fiducial cosmology. If we adopt a parametrization such that f=Ωγm(z), with γ≈ 0.55 in GR, and combine our fσ8 measurement with the corresponding ones from spectroscopic LRGs at lower redshifts, we obtain γ= 0.54 ± 0.17. In addition we find evidence for the presence of the baryon acoustic feature matching the amplitude, location and shape of ΛCDM predictions. The photometric BAO feature is detected with 98 per cent confidence level at z= 0.55. © 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS.

Wilson-Hodge C.A.,NASA | Case G.L.,Louisiana State University | Cherry M.L.,Louisiana State University | Rodi J.,Louisiana State University | And 14 more authors.
Astrophysical Journal, Supplement Series | Year: 2012

The Gamma-ray Burst Monitor (GBM) on board Fermi has been providing continuous data to the astronomical community since 2008 August 12. In this paper, we present the results of the analysis of the first three years of these continuous data using the Earth occultation technique to monitor a catalog of 209 sources. From this catalog, we detect 99 sources, including 40 low-mass X-ray binary/neutron star systems, 31 high-mass X-ray binary/neutron star systems, 12 black hole binaries, 12 active galaxies, and 2 other sources, plus the Crab Nebula, and the Sun. Nine of these sources are detected in the 100-300keV band, including seven black hole binaries, the active galaxy CenA, and the Crab. The Crab and CygX-1 are also detected in the 300-500keV band. GBM provides complementary data to other sky-monitors below 100keV and is the only all-sky monitor above 100keV. Up-to-date light curves for all of the catalog sources can be found online. © © 2012. The American Astronomical Society. All rights reserved.

Mannarelli M.,Institute Ciencias del Espacio IEEC CSIC | Giannuzzi F.,National Institute of Nuclear Physics, Italy | Giannuzzi F.,University of Bari
Acta Physica Polonica B, Proceedings Supplement | Year: 2010

We investigate the properties of charmonia in a thermal medium, showing that with increasing temperature the decay widths of these mesons behave in a non-trivial way. Employing a potential model with interaction potential extracted from thermal lattice QCD calculations of the free-energy of a static quark-antiquark pair, we study some decay processes in the crossover region. We find that at temperatures T ∼ Tc the decay widths of the J/Ψ that depend on the value of the wave function at the origin are enhanced with respect to the values in vacuum. In the same temperature range the decay width of the process ΧcJ → J/Ψ + γ is enhanced by approximately a factor 6 with respect to the value in vacuum. At higher temperatures the charmonia states dissociate and the widths of both decay processes become vanishing small.

Manuel C.,Institute Ciencias Del Espacio IEEC CSIC | Soto J.,University of Barcelona | Stetina S.,University of Washington
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2016

We show that effective field theory techniques can be efficiently used to compute power corrections to the hard thermal loops in a high temperature T expansion. To this aim, we use the recently proposed on-shell effective field theory, which describes the quantum fluctuations around on-shell degrees of freedom. We provide the on-shell effective field theory Lagrangian up to third order in the energy expansion for QED and use it for the computation of power corrections to the retarded photon polarization tensor for soft external momenta. Here soft denotes a scale of order eT, where e is the gauge coupling constant. We develop the necessary techniques to perform these computations and study the contributions to the polarization tensor proportional to e2T2, e2T, and e2T0. The first one describes the hard thermal loop contribution, the second one vanishes, while the third one provides corrections of order e2 to the soft photon propagation. We check that the results agree with the direct calculation from QED, up to local pieces, as expected in an effective field theory. © 2016 American Physical Society.

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