Recent Postings from astro-ph

The PDF4LHC report on PDFs and LHC data: Results from Run I and preparation for Run II [Cross-Listing]

The accurate determination of the Parton Distribution Functions (PDFs) of the proton is an essential ingredient of the Large Hadron Collider (LHC) program. PDF uncertainties impact a wide range of processes, from Higgs boson characterisation and precision Standard Model measurements to New Physics searches. A major recent development in modern PDF analyses has been to exploit the wealth of new information contained in precision measurements from the LHC Run I, as well as progress in tools and methods to include these data in PDF fits. In this report we summarise the information that PDF-sensitive measurements at the LHC have provided so far, and review the prospects for further constraining PDFs with data from the recently started Run II. This document aims to provide useful input to the LHC collaborations to prioritise their PDF-sensitive measurements at Run II, as well as a comprehensive reference for the PDF-fitting collaborations.

Massive $2$-form field and holographic ferromagnetic phase transition

In this paper, we investigate in some detail the holographic ferromagnetic phase transition in an AdS${_4}$ black brane background by introducing a massive 2-form field coupled to the Maxwell field strength in the bulk. In the two probe limits, one is to neglect the back reaction of the 2-form field to the background geometry and to the Maxwell field, and the other to neglect the back reaction of both the Maxwell field and the 2-form field, we find that the spontaneous magnetization and the ferromagnetic phase transition always happen when the temperature gets low enough with similar critical behavior. We calculate the DC resistivity in a semi-analytical method in the second probe limit and find it behaves as the colossal magnetic resistance effect in some materials. In the case with the first probe limit, we obtain the off-shell free energy of the holographic model near the critical temperature and compare with the Ising-like model. We also study the back reaction effect and find that the phase transition is always second order. In addition, we find an analytical Reissner-Norstr\"om-like black brane solution in the Einstein-Maxwell-2-form field theory with a negative cosmological constant.

Massive $2$-form field and holographic ferromagnetic phase transition [Cross-Listing]

In this paper, we investigate in some detail the holographic ferromagnetic phase transition in an AdS${_4}$ black brane background by introducing a massive 2-form field coupled to the Maxwell field strength in the bulk. In the two probe limits, one is to neglect the back reaction of the 2-form field to the background geometry and to the Maxwell field, and the other to neglect the back reaction of both the Maxwell field and the 2-form field, we find that the spontaneous magnetization and the ferromagnetic phase transition always happen when the temperature gets low enough with similar critical behavior. We calculate the DC resistivity in a semi-analytical method in the second probe limit and find it behaves as the colossal magnetic resistance effect in some materials. In the case with the first probe limit, we obtain the off-shell free energy of the holographic model near the critical temperature and compare with the Ising-like model. We also study the back reaction effect and find that the phase transition is always second order. In addition, we find an analytical Reissner-Norstr\"om-like black brane solution in the Einstein-Maxwell-2-form field theory with a negative cosmological constant.

Heliosphere for a wide range of interstellar magnetic field strengths as a source of energetic neutral atoms

Observations of the energetic neutral atoms (ENAs) of heliospheric origin by IBEX differ from expectations based on heliospheric models. It was proposed that the structure of the heliosphere may be similar to the "two-stream" model derived in 1961 by Parker for the case of strong interstellar magnetic field. Using MHD simulations, we examine possible structure of the heliosphere for a wide range of interstellar magnetic field strengths, with different choices of interstellar medium and solar wind parameters. For the model heliospheres, we calculate the fluxes of ENAs created in the inner heliosheath, and compare with IBEX observations. We find that the plasma flow in the model heliospheres for strong interstellar field ($\sim$20 $\mu$G) has a "two-stream" structure, which remains visible down to $\sim$5 $\mu$G. The obtained ENA flux distribution show the features similar to the "split tail" effect observed by IBEX. In our model, the main cause of this effect is the two component (fast and slow) solar wind structure.

Relationship between the column density distribution and evolutionary class of molecular clouds as viewed by ATLASGAL

We present the first study of the relationship between the column density distribution of molecular clouds within nearby Galactic spiral arms and their evolutionary status as measured from their stellar content. We analyze a sample of 195 molecular clouds located at distances below 5.5 kpc, identified from the ATLASGAL 870 micron data. We define three evolutionary classes within this sample: starless clumps, star-forming clouds with associated young stellar objects, and clouds associated with HII regions. We find that the N(H2) probability density functions (N-PDFs) of these three classes of objects are clearly different: the N-PDFs of starless clumps are narrowest and close to log-normal in shape, while star-forming clouds and HII regions exhibit a power-law shape over a wide range of column densities and log-normal-like components only at low column densities. We use the N-PDFs to estimate the evolutionary time-scales of the three classes of objects based on a simple analytic model from literature. Finally, we show that the integral of the N-PDFs, the dense gas mass fraction, depends on the total mass of the regions as measured by ATLASGAL: more massive clouds contain greater relative amounts of dense gas across all evolutionary classes.

Detecting gravitational-wave transients at five sigma: a hierarchical approach

As second-generation gravitational-wave detectors prepare to analyze data at unprecedented sensitivity, there is great interest in searches for unmodeled transients, commonly called bursts. Significant effort has yielded a variety of techniques to identify and characterize such transient signals, and many of these methods have been applied to produce astrophysical results using data from first-generation detectors. However, the computational cost of background estimation remains a challenging problem; it is difficult to claim a 5{\sigma} detection with reasonable computational resources without paying for efficiency with reduced sensitivity. We demonstrate a hierarchical approach to gravitational-wave transient detection, focusing on long-lived signals, which can be used to detect transients with significance in excess of 5{\sigma} using modest computational resources. In particular, we show how previously developed seedless clustering techniques can be applied to large datasets to identify high-significance candidates without having to trade sensitivity for speed.

Detecting gravitational-wave transients at five sigma: a hierarchical approach [Cross-Listing]

As second-generation gravitational-wave detectors prepare to analyze data at unprecedented sensitivity, there is great interest in searches for unmodeled transients, commonly called bursts. Significant effort has yielded a variety of techniques to identify and characterize such transient signals, and many of these methods have been applied to produce astrophysical results using data from first-generation detectors. However, the computational cost of background estimation remains a challenging problem; it is difficult to claim a 5{\sigma} detection with reasonable computational resources without paying for efficiency with reduced sensitivity. We demonstrate a hierarchical approach to gravitational-wave transient detection, focusing on long-lived signals, which can be used to detect transients with significance in excess of 5{\sigma} using modest computational resources. In particular, we show how previously developed seedless clustering techniques can be applied to large datasets to identify high-significance candidates without having to trade sensitivity for speed.

A divergence free parametrization of deceleration parameter for scalar field dark energy

In this paper, we have considered a spatially flat FRW universe filled with pressureless matter and dark energy. We have considered a phenomenological parametrization of the deceleration parameter $q(z)$ and from this we have reconstructed the equation of state for dark energy $\omega_{\phi}(z)$. Using the combination of datasets (SN Ia + Hubble + BAO/CMB), we have constrained the transition redshift $z_t$ (at which the universe switches from a decelerating to an accelerating phase) and have found the best fit value of $z_t$. We have also found that the reconstructed results of $q(z)$ and $\omega_{\phi}(z)$ are in good agreement with the recent observations. The potential term for the present toy model is found to be functionally similar to a Higgs potential.

A divergence free parametrization of deceleration parameter for scalar field dark energy [Cross-Listing]

In this paper, we have considered a spatially flat FRW universe filled with pressureless matter and dark energy. We have considered a phenomenological parametrization of the deceleration parameter $q(z)$ and from this we have reconstructed the equation of state for dark energy $\omega_{\phi}(z)$. Using the combination of datasets (SN Ia + Hubble + BAO/CMB), we have constrained the transition redshift $z_t$ (at which the universe switches from a decelerating to an accelerating phase) and have found the best fit value of $z_t$. We have also found that the reconstructed results of $q(z)$ and $\omega_{\phi}(z)$ are in good agreement with the recent observations. The potential term for the present toy model is found to be functionally similar to a Higgs potential.

Super Massive Black Holes and the Origin of High-Velocity Stars

The origin of high velocity stars observed in the halo of our Galaxy is still unclear. In this work we test the hypothesis, raised by results of recent high precision $N$-body simulations, of strong acceleration of stars belonging to a massive globular cluster orbitally decayed in the central region of the host galaxy where it suffers of a close interaction with a super massive black hole, which, for these test cases, we assumed $10^8$ M$_\odot$ in mass.

Quantum spectral curve for (q,t)-matrix model

We derive quantum spectral curve equation for (q,t)-matrix model, which turns out to be a certain difference equation. We show that in Nekrasov-Shatashvili limit this equation reproduces the Baxter TQ equation for the quantum XXZ spin chain. This chain is spectral dual to the Seiberg-Witten integrable system associated with the AGT dual gauge theory.

Solar and Heliospheric Physics with the Square Kilometre Array

The fields of solar radiophysics and solar system radio physics, or radio heliophysics, will benefit immensely from an instrument with the capabilities projected for SKA. Potential applications include interplanetary scintillation (IPS), radio-burst tracking, and solar spectral radio imaging with a superior sensitivity. These will provide breakthrough new insights and results in topics of fundamental importance, such as the physics of impulsive energy releases, magnetohydrodynamic oscillations and turbulence, the dynamics of post-eruptive processes, energetic particle acceleration, the structure of the solar wind and the development and evolution of solar wind transients at distances up to and beyond the orbit of the Earth. The combination of the high spectral, time and spatial resolution and the unprecedented sensitivity of the SKA will radically advance our understanding of basic physical processes operating in solar and heliospheric plasmas and provide a solid foundation for the forecasting of space weather events.

The Most Intensive Gamma-Ray Flare of Quasar 3C 279 with the Second-Order Fermi Acceleration

The very short and bright flare of 3C 279 detected with {\it Fermi}-LAT in 2013 December is tested by a model with stochastic electron acceleration by turbulences. Our time-dependent simulation shows that the very hard spectrum and asymmetric lightcurve are successfully reproduced by changing only the magnetic field from the value in the steady period. The maximum energy of electrons drastically grows by the decrease of the magnetic field, which yields hard photon spectrum as observed. Succeeding rapid cooling due to the inverse Compton scattering with the external photons reproduces the decaying feature of the lightcurve. The inferred energy density of the magnetic field is much less than the electron and photon energy densities. The low magnetic field and short variability timescale are unfavorable for the jet acceleration model by the gradual Poynting flux dissipation.

Evolution of Primordial Magnetic Fields: From Generation Till Today

In this presentation we summarize our previous results concerning the evolution of primordial magnetic fields with and without helicity during the expansion of the Universe. We address different magnetogenesis scenarios such as inflation, electroweak and QCD phase transitions magnetogenesis. A high Reynolds number in the early Universe ensures strong coupling between magnetic field and fluid motions. After generation the subsequent dynamics of the magnetic field is governed by decaying hydromagnetic turbulence. We claim that primordial magnetic fields can be considered as a seeds for observed magnetic fields in galaxies and clusters. Magnetic field strength bounds obtained in our analysis are consistent with the upper and lower limits of extragalactic magnetic fields.

QCD-aware partonic jet clustering for truth-jet flavour labelling

We present an algorithm for deriving partonic flavour labels to be applied to truth par- ticle jets in Monte Carlo event simulations. The inputs to this approach are final pre- hadronization partons, to remove dependence on unphysical details such as the order of matrix element calculation and shower generator frame recoil treatment. These are clus- tered using standard jet algorithms, modified to restrict the allowed pseudojet combina- tions to those in which tracked flavour labels are consistent with QCD and QED Feynman rules. The resulting algorithm is shown to be portable between the major families of shower generators, and largely insensitive to many possible systematic variations: it hence offers significant advantages over existing ad hoc labelling schemes. However, it is shown that contamination from multi-parton scattering simulations can disrupt the labelling results. Suggestions are made for further extension to incorporate more detailed QCD splitting function kinematics, robustness improvements, and potential uses for truth-level physics object definitions and tagging.

Effect of Stellar Encounters on Comet Cloud Formation

We have investigated the effect of stellar encounters on the formation and disruption of the Oort cloud using the classical impulse approximation. We calculate the evolution of a planetesimal disk into a spherical Oort cloud due to the perturbation from passing stars for 10 Gyr. We obtain the empirical fits of the $e$-folding time for the number of Oort cloud comets using the standard exponential and Kohlrausch formulae as functions of the stellar parameters and the initial semimajor axes of planetesimals. The $e$-folding time and the evolution timescales of the orbital elements are also analytically derived. In some calculations, the effect of the Galactic tide is additionally considered. We also show the radial variations of the $e$-folding times to the Oort cloud. From these timescales, we show that if the initial planetesimal disk has the semimajor axes distribution ${\rm d}n/{\rm d}a\propto a^{-2}$, which is produced by planetary scattering (Higuchi et al. 2006), the $e$-folding time for planetesimals in the Oort cloud is $\sim$10 Gyr at any heliocentric distance $r$. This uniform $e$-folding time over the Oort cloud means that the supply of comets from the inner Oort cloud to the outer Oort cloud is sufficiently effective to keep the comet distribution as ${\rm d}n/{\rm d}r\propto r^{-2}$. We also show that the final distribution of the semimajor axes in the Oort cloud is approximately proportional to $a^{-2}$ for any initial distribution.

Distributed image reconstruction for very large arrays in radio astronomy

Current and future radio interferometric arrays such as LOFAR and SKA are characterized by a paradox. Their large number of receptors (up to millions) allow theoretically unprecedented high imaging resolution. In the same time, the ultra massive amounts of samples makes the data transfer and computational loads (correlation and calibration) order of magnitudes too high to allow any currently existing image reconstruction algorithm to achieve, or even approach, the theoretical resolution. We investigate here decentralized and distributed image reconstruction strategies which select, transfer and process only a fraction of the total data. The loss in MSE incurred by the proposed approach is evaluated theoretically and numerically on simple test cases.

ANNz2 - Photometric redshift and probability density function estimation using machine learning methods

We present ANNz2, a new implementation of the public software for photometric redshift (photo-z) estimation of Collister and Lahav (2004). Large photometric galaxy surveys are important for cosmological studies, and in particular for characterizing the nature of dark energy. The success of such surveys greatly depends on the ability to measure photo-zs, based on limited spectral data. ANNz2 utilizes multiple machine learning methods, such as artificial neural networks, boosted decision/regression trees and k-nearest neighbours. The objective of the algorithm is to dynamically optimize the performance of the photo-z estimation, and to properly derive the associated uncertainties. In addition to single-value solutions, the new code also generates full probability density functions (PDFs) in two different ways. In addition, estimators are incorporated to mitigate possible problems of spectroscopic training samples which are not representative or are incomplete. ANNz2 is also adapted to provide optimized solutions to general classification problems, such as star/galaxy separation. We illustrate the functionality of the code using data from the tenth data release of the Sloan Digital Sky Survey and the Baryon Oscillation Spectroscopic Survey. The code is available for download at https://github.com/IftachSadeh/ANNZ

Super Virasoro Algebras From Chiral Supergravity

In this note, we construct Noether charges for the chiral supergravity, which contains the Lorentz Chern-Simons term, by applying Wald’s prescription to the vielbein formalism. We investigate the AdS3/CFT2 correspondence by using the vielbein formalism. The asymptotic symmetry group is carefully examined by taking into account the local Lorentz transformation, and we construct super Virasoro algebras with central extensions from the chiral supergravity.

Two-Hadron Saturation for the Pseudoscalar-Vector-Vector Correlator and Phenomenological Applications [Cross-Listing]

The pseudoscalar-vector-vector correlator is constructed using two meson multiplets in the vector and two in the pseudoscalar channel. The parameters are constrained by the operator product expansion at leading order where two or all three momenta are considered as large. Demanding in addition the Brodsky-Lepage limit one obtains (in the chiral limit) a pion-vector-vector correlator with only one free parameter. The singly virtual pion transition form factor and the decay width of omega to pion and photon are independent of this parameter and can serve as cross-checks of the results. The free parameter is determined from a fit of the omega-pion transition form factor. The resulting pion-vector-vector correlator is used to calculate the decay widths of omega to pion and dielectron and to pion and dimuon and finally the widths of the rare decay pion to dielectron and of the Dalitz decay pion to photon and dielectron. Incorporating radiative QED corrections the calculations of neutral-pion decays are compared to the KTeV results. We find a deviation of 2 sigma or less for the rare pion decay.

Two-Hadron Saturation for the Pseudoscalar-Vector-Vector Correlator and Phenomenological Applications

The pseudoscalar-vector-vector correlator is constructed using two meson multiplets in the vector and two in the pseudoscalar channel. The parameters are constrained by the operator product expansion at leading order where two or all three momenta are considered as large. Demanding in addition the Brodsky-Lepage limit one obtains (in the chiral limit) a pion-vector-vector correlator with only one free parameter. The singly virtual pion transition form factor and the decay width of omega to pion and photon are independent of this parameter and can serve as cross-checks of the results. The free parameter is determined from a fit of the omega-pion transition form factor. The resulting pion-vector-vector correlator is used to calculate the decay widths of omega to pion and dielectron and to pion and dimuon and finally the widths of the rare decay pion to dielectron and of the Dalitz decay pion to photon and dielectron. Incorporating radiative QED corrections the calculations of neutral-pion decays are compared to the KTeV results. We find a deviation of 2 sigma or less for the rare pion decay.

The Cauchy problem in General Relativity: An algebraic characterization

In this paper we shall analyse the structure of the Cauchy Problem (CP briefly) for General Relativity (GR briefly) by applying the theory of first order symmetric hyperbolic systems.

Detailed photospheric abundances of 28 Peg and HD 202240

The atmospheric parameters and chemical abundances of two neglected A-type stars, 28 Peg and HD 202240, were derived using high resolution spectra obtained at the TUBITAK National Observatory. We determined the photospheric abundances of eleven elements for 28 Peg and twenty for HD 202240, using equivalent-width measurement and spectral synthesis methods. Their abundance patterns are in good agreement with those of chemically normal A-type stars having similar atmospheric parameters. We pinpoint the position of these stars on the H-R diagram and estimate their masses and ages as; $2.60\pm0.10\ M_\odot$ and $650\pm50\ Myr$ for 28 Peg and $4.50\pm0.09\ M_\odot$ and $150\pm10\ Myr$ for HD 202240. To compare our abundance determinations with those of stars having similar ages and atmospheric parameters, we select members of open clusters. We notice that our target stars exhibit similar abundance patterns with these members.

Variation of the baryon-to-photon ratio due to decay of dark matter particles

The influence of dark matter particle decay on the baryon-to-photon ratio has been studied for different cosmological epochs. We consider different parameter values of dark matter particles such as mass, lifetime, the relative fraction of dark matter particles. It is shown that the modern value of the dark matter density $\Omega_{\rm CDM}=0.26$ is enough to lead to variation of the baryon-to-photon ratio up to $\Delta \eta / \eta \sim 0.01 \div 1$ for decays of the particles with masses 10 GeV $\div$ 1 TeV. However, such processes can also be accompanied by emergence of an excessive gamma ray flux. The observational data on the diffuse gamma ray background are used to making constraints on the dark matter decay models and on the maximum possible variation of the baryon-to-photon ratio $\Delta\eta/\eta\lesssim10^{-5}$. Detection of such variation of the baryon density in future cosmological experiments can serve as a powerful means of studying properties of dark matter particles.

Boundary Operators of BCFW Recursion Relation

We show that boundary contributions of BCFW recursions are related to some composite operators which we call ‘boundary operators’. These boundary operators can be extracted from the operator product expansion of deformed fields. We present an algorithm to derive boundary operators and then demonstrate it in several examples, including scalar theories, non-linear sigma model and Yukawa theory.

Dark matter, Mach's ether and the QCD vacuum [Cross-Listing]

Here is proposed the idea of linking the dark matter issue, (considered as a major problem of contemporary research in physics) with two other open theoretical questions, one, almost centenary about the existence of an unavoidable ether in general relativity agreeing with the Mach’s principle, and one more recent about the properties of the quantum vacuum of the quantum field theory of strong interactions, QuantumChromodynamics (QCD). According to this idea, on the one hand, dark matter and dark energy that, according to the current standard model of cosmology represent about 95% of the universe content, can be considered as two distinct forms of the Mach’s ether, and, on the other hand, dark matter, as a perfect fluid emerging from the QCD vacuum could be modeled as a Bose Einstein condensate.

Can Family Gauge Bosons Be Visible by Terrestrial Experiments?

It is investigated whether observations of family gauge bosons by terrestrial experiments are possible or not. We propose an extended version of Sumino’s family gauge boson model based on U(3) family symmetry. Then, we can expect the lowest family gauge boson $A_1^1$ with $M \sim 4.3$ TeV.

Exact results for Wilson loops in orbifold ABJM theory [Cross-Listing]

We investigate the exact results for circular 1/4 and 1/2 BPS Wilson loops in the d=3 N=4 super Chern-Simons-matter theory that could be obtained by orbifolding Aharony-Bergman-Jafferis-Maldacena (ABJM) theory. In literature there is the partition function of the N=4 orbifold ABJM theory, and we re-derive it in a slightly different method. We calculate the vacuum expectation values of the circular 1/4 and 1/2 BPS Wilson loops in both the saddle point approach and Fermi gas approach, and the results are in accord to the gravity ones.

Exact results for Wilson loops in orbifold ABJM theory

We investigate the exact results for circular 1/4 and 1/2 BPS Wilson loops in the d=3 N=4 super Chern-Simons-matter theory that could be obtained by orbifolding Aharony-Bergman-Jafferis-Maldacena (ABJM) theory. In literature there is the partition function of the N=4 orbifold ABJM theory, and we re-derive it in a slightly different method. We calculate the vacuum expectation values of the circular 1/4 and 1/2 BPS Wilson loops in both the saddle point approach and Fermi gas approach, and the results are in accord to the gravity ones.

Effects of the scalar mesons in a Skyrme model with hidden local symmetry

We study the effects of light scalar mesons on the skyrmion properties by first constructing a mesonic model including pion, rho and omega mesons as well as a two-quark and a four-quark scalar states. In our model, the physical scalar mesons are defined as mixing states of the two- and four-quark states. We find that the scalar mesons reduce the skyrmion mass as expected and the lighter scalar meson is, the smaller soliton mass and larger soliton size become when there are no direct coupling between the scalar mesons and the vector mesons. When the direct coupling becomes stronger, the soliton becomes heavier and the charge radius of the baryon number density becomes larger since the repulsive force arising from the $\omega$ meson becomes stronger. For the effect of the mixing, we find that, when the magnitude of the two-quark component of the lighter scalar meson is increased, the soliton mass becomes smaller and the soliton size becomes larger.

Ellerman bombs at high resolution III. Simultaneous observations with IRIS and SST

Ellerman bombs are transient brightenings of the extended wings of the solar Balmer lines in emerging active regions. We describe their properties in the ultraviolet lines sampled by the Interface Region Imaging Spectrograph (IRIS), using simultaneous imaging spectroscopy in H$\alpha$ with the Swedish 1-m Solar Telescope (SST) and ultraviolet images from the Solar Dynamics Observatory for Ellerman bomb detection and identification. We select multiple co-observed Ellerman bombs for detailed analysis. The IRIS spectra strengthen the view that Ellerman bombs mark reconnection between bipolar kilogauss fluxtubes with the reconnection and the resulting bi-directional jet located within the solar photosphere and shielded by overlying chromospheric fibrils in the cores of strong lines. The spectra suggest that the reconnecting photospheric gas underneath is heated sufficiently to momentarily reach stages of ionization normally assigned to the transition region and the corona. We also analyze similar outburst phenomena that we classify as small flaring arch filaments and ascribe to higher-located reconnection. They have different morphology and produce hot arches in million-Kelvin diagnostics.

Spontaneous parametric down conversion with a depleted pump as an analogue for black hole evaporation/particle production [Cross-Listing]

We present an analytical formulation of the recent one-shot decoupling model of Br\`adler and Adami [arXiv:1505.0284] and compute the resulting "Page Information" curves, for the reduced density matrices for the evaporating black hole internal degrees of freedom, and emitted Hawking radiation pairs entangled across the horizon. We argue that black hole evaporation/particle production has a very close analogy to the laboratory process of spontaneous parametric down conversion, when the pump is allowed to deplete.

Spontaneous parametric down conversion with a depleted pump as an analogue for black hole evaporation/particle production [Cross-Listing]

We present an analytical formulation of the recent one-shot decoupling model of Br\`adler and Adami [arXiv:1505.0284] and compute the resulting "Page Information" curves, for the reduced density matrices for the evaporating black hole internal degrees of freedom, and emitted Hawking radiation pairs entangled across the horizon. We argue that black hole evaporation/particle production has a very close analogy to the laboratory process of spontaneous parametric down conversion, when the pump is allowed to deplete.

The Calcium Triplet metallicity calibration for galactic bulge stars

We present a new calibration of the Calcium II Triplet equivalent widths versus [Fe/H], constructed upon K giant stars in the Galactic bulge. This calibration will be used to derive iron abundances for the targets of the GIBS survey, and in general it is especially suited for solar and supersolar metallicity giants, typical of external massive galaxies. About 150 bulge K giants were observed with the GIRAFFE spectrograph at VLT, both at resolution R~20,000 and at R~6,000. In the first case, the spectra allowed us to perform direct determination of Fe abundances from several unblended Fe lines, deriving what we call here high resolution [Fe/H] measurements. The low resolution spectra allowed us to measure equivalent widths of the two strongest lines of the near infrared Calcium II triplet at 8542 and 8662 A. By comparing the two measurements we derived a relation between Calcium equivalent widths and [Fe/H] that is linear over the metallicity range probed here, -1<[Fe/H]<+0.7. By adding a small second order correction, based on literature globular cluster data, we derived the unique calibration equation [Fe/H]$_{CaT} = -3.150 + 0.432W’ + 0.006W’^2$, with a rms dispersion of 0.197 dex, valid across the whole metallicity range -2.3<[Fe/H]<+0.7.

Physical Dust Models for the Extinction toward Supernova 2014J in M82

Type Ia supernovae (SNe Ia) are powerful cosmological "standardizable candles" and the most precise distance indicators. However, a limiting factor in their use for precision cosmology rests on our ability to correct for the dust extinction toward them. SN 2014J in the starburst galaxy M82, the closest detected SN~Ia in three decades, provides unparalleled opportunities to study the dust extinction toward an SN Ia. In order to derive the extinction as a function of wavelength, we model the color excesses toward SN 2014J, which are observationally derived over a wide wavelength range in terms of dust models consisting of a mixture of silicate and graphite. The resulting extinction laws steeply rise toward the far ultraviolet, even steeper than that of the Small Magellanic Cloud (SMC). We infer a visual extinction of $A_V \approx 1.9~\rm mag$, a reddening of $E(B-V)\approx1.1~ \rm mag$, and a total-to-selective extinction ratio of $R_V \approx 1.7$, consistent with that previously derived from photometric, spectroscopic, and polarimetric observations. The size distributions of the dust in the interstellar medium toward SN 2014J are skewed toward substantially smaller grains than that of the Milky Way and the SMC.

Spectral breaks of Alfvenic turbulence in a collisionless plasma [Cross-Listing]

Recent observations reveal that magnetic turbulence in the nearly colisionless solar wind plasma extends to scales smaller than the plasma microscales, such as ion gyroradius and ion inertial length. Measured breaks in the spectra of magnetic and density fluctuations at high frequencies are thought to be related to the transition from large-scale hydromagnetic to small-scale kinetic turbulence. The scales of such transitions and the responsible physical mechanisms are not well understood however. In the present work we emphasize the crucial role of the plasma parameters in the transition to kinetic turbulence, such as the ion and electron plasma beta, the electron to ion temperature ratio, the degree of obliquity of turbulent fluctuations. We then propose an explanation for the spectral breaks reported in recent observations.

Automated Kinematic Modelling of Warped Galaxy Discs in Large Hi Surveys: 3D Tilted Ring Fitting of HI Emission Cubes

Kinematical parameterisations of disc galaxies, employing emission line observations, are indispensable tools for studying the formation and evolution of galaxies. Future large-scale HI surveys will resolve the discs of many thousands of galaxies, allowing a statistical analysis of their disc and halo kinematics, mass distribution and dark matter content. Here we present an automated procedure which fits tilted-ring models to Hi data cubes of individual, well-resolved galaxies. The method builds on the 3D Tilted Ring Fitting Code (TiRiFiC) and is called FAT (Fully Automated TiRiFiC). To assess the accuracy of the code we apply it to a set of 52 artificial galaxies and 25 real galaxies from the Local Volume HI Survey (LVHIS). Using LVHIS data, we compare our 3D modelling to the 2D modelling methods DiskFit and rotcur. A conservative result is that FAT accurately models the kinematics and the morphologies of galaxies with an extent of eight beams across the major axis in the inclination range 20$^{\circ}$-90$^{\circ}$ without the need for priors such as disc inclination. When comparing to 2D methods we find that velocity fields cannot be used to determine inclinations in galaxies that are marginally resolved. We conclude that with the current code tilted-ring models can be produced in a fully automated fashion. This will be essential for future HI surveys, with the Square Kilometre Array and its pathfinders, which will allow us to model the gas kinematics of many thousands of well-resolved galaxies. Performance studies of FAT close to our conservative limits, as well as the introduction of more parameterised models will open up the possibility to study even less resolved galaxies.

Resurgence in sine-Gordon quantum mechanics: Exact agreement between multi-instantons and uniform WKB

We compute multi-instanton amplitudes in the sine-Gordon quantum mechanics (periodic cosine potential) by integrating out quasi-moduli parameters corresponding to separations of instantons and anti-instantons. We propose an extension of Bogomolnyi–Zinn-Justin prescription for multi-instanton configurations and an appropriate subtraction scheme. We obtain the multi-instanton contributions to the energy eigenvalue of the lowest band at the zeroth order of the coupling constant. For the configurations with only instantons (anti-instantons), we obtain unambiguous results. For those with both instantons and anti-instantons, we obtain results with imaginary parts, which depend on the path of analytic continuation. We show that the imaginary parts of the multi-instanton amplitudes precisely cancel the imaginary parts of the Borel resummation of the perturbation series, and verify that our results completely agree with those based on the uniform-WKB calculations, thus confirming the resurgence : divergent perturbation series combined with the nonperturbative multi-instanton contributions conspire to give unambiguous results. We also study the neutral bion contributions in the ${\mathbb C}P^{N-1}$ model on ${\mathbb R}^1\times S^{1}$ with a small circumference, taking account of the relative phase moduli between the fractional instanton and anti-instanton. We find that the sign of the interaction potential depends on the relative phase moduli, and that both the real and imaginary parts resulting from quasi-moduli integral of the neutral bion get quantitative corrections compared to the sine-Gordon quantum mechanics.

Resurgence in sine-Gordon quantum mechanics: Exact agreement between multi-instantons and uniform WKB [Cross-Listing]

We compute multi-instanton amplitudes in the sine-Gordon quantum mechanics (periodic cosine potential) by integrating out quasi-moduli parameters corresponding to separations of instantons and anti-instantons. We propose an extension of Bogomolnyi–Zinn-Justin prescription for multi-instanton configurations and an appropriate subtraction scheme. We obtain the multi-instanton contributions to the energy eigenvalue of the lowest band at the zeroth order of the coupling constant. For the configurations with only instantons (anti-instantons), we obtain unambiguous results. For those with both instantons and anti-instantons, we obtain results with imaginary parts, which depend on the path of analytic continuation. We show that the imaginary parts of the multi-instanton amplitudes precisely cancel the imaginary parts of the Borel resummation of the perturbation series, and verify that our results completely agree with those based on the uniform-WKB calculations, thus confirming the resurgence : divergent perturbation series combined with the nonperturbative multi-instanton contributions conspire to give unambiguous results. We also study the neutral bion contributions in the ${\mathbb C}P^{N-1}$ model on ${\mathbb R}^1\times S^{1}$ with a small circumference, taking account of the relative phase moduli between the fractional instanton and anti-instanton. We find that the sign of the interaction potential depends on the relative phase moduli, and that both the real and imaginary parts resulting from quasi-moduli integral of the neutral bion get quantitative corrections compared to the sine-Gordon quantum mechanics.

Post-newtonian analysis of precessing convention for spinning compact binaries

A precessing source frame, constructed using the Newtonian orbital angular momentum ${\bf L_{\rm N}}$, can be invoked to model inspiral gravitational waves from generic spinning compact binaries. An attractive feature of such a precessing convention is its ability to remove all spin precession induced modulations from the orbital phase evolution. However, this convention usually employs a post-Newtonian (PN) accurate precessional equation, appropriate for the PN accurate orbital angular momentum ${\bf L}$, to evolve the ${\bf L_{\rm N}}$-based precessing source frame. This influenced us to develop inspiral waveforms for spinning compact binaries in a precessing convention that explicitly employ ${\bf L}$ to describe the binary orbits. Our approach introduces certain additional 3PN order terms in the evolution equations for the orbital phase and frequency with respect to the usual ${\bf L_{\rm N}}$-based implementation of the precessing convention. We examine the practical implications of these additional terms by computing the match between inspiral waveforms that employ ${\bf L}$ and ${\bf L_{\rm N}}$-based precessing conventions. The match estimates are found to be smaller than the optimal value, namely $0.97$, for a non-negligible fraction of unequal mass spinning compact binaries.

How to build a compact brane [Cross-Listing]

This work deals with braneworld models in a five dimensional curved geometry with a single extra dimension of infinite extent. The investigation introduces a new family of models, generated from a source scalar field that supports kinklike structures described through the presence of a real parameter, capable of controlling the thickness of the warp factor that describes the five dimensional geometry. The mechanism shows how to get a brane that engenders a compact profile.

How to build a compact brane

This work deals with braneworld models in a five dimensional curved geometry with a single extra dimension of infinite extent. The investigation introduces a new family of models, generated from a source scalar field that supports kinklike structures described through the presence of a real parameter, capable of controlling the thickness of the warp factor that describes the five dimensional geometry. The mechanism shows how to get a brane that engenders a compact profile.

How to build a compact brane [Cross-Listing]

This work deals with braneworld models in a five dimensional curved geometry with a single extra dimension of infinite extent. The investigation introduces a new family of models, generated from a source scalar field that supports kinklike structures described through the presence of a real parameter, capable of controlling the thickness of the warp factor that describes the five dimensional geometry. The mechanism shows how to get a brane that engenders a compact profile.

A practical parametrization for line shapes of near-threshold states

We propose a practical parametrization for the line shapes of near-threshold states compatible with all requirements of unitarity and analyticity. The coupled-channel system underlying the proposed parametrization includes a bare pole and an arbitrary number of elastic and inelastic channels treated fully nonperturbatively. The resulting formulas are general enough to be used for a simultaneous analysis of the data in all available production and decay channels of a given (system of) state(s) for a quite wide class of reactions. As an example, we fit the experimental data currently available for several decay channels for the charged $Z_b(10610)$ and $Z_b(10650)$ states in the spectrum of bottomonia and find a remarkably good overall description of the data.

The I-Q relations for rapidly rotating neutron stars in $f(R)$ gravity

In the present paper we study the behavior of the normalized $I$-$Q$ relation for neutron stars in a particular class of $f(R)$ theories of gravity, namely the $R^2$ gravity that is one of the most natural and simplest extensions of general relativity in the strong field regime. We study both the slowly and rapidly rotating cases. The results show that the $I$-$Q$ relation remain nearly equation of state independent for fixed values of the normalized rotational parameter, but the deviations from universality can be a little bit larger compared to the general relativistic case. What is the most interesting in our studies, is that the differences with the pure Einstein’s theory can be large reaching above 20\%. This is qualitative different from the majority of alternative theories of gravity, where the normalized $I$-$Q$ relations are almost indistinguishable from the general relativistic case, and can lead to observational constraints on the $f(R)$ theories in the future.

The I-Q relations for rapidly rotating neutron stars in $f(R)$ gravity [Cross-Listing]

In the present paper we study the behavior of the normalized $I$-$Q$ relation for neutron stars in a particular class of $f(R)$ theories of gravity, namely the $R^2$ gravity that is one of the most natural and simplest extensions of general relativity in the strong field regime. We study both the slowly and rapidly rotating cases. The results show that the $I$-$Q$ relation remain nearly equation of state independent for fixed values of the normalized rotational parameter, but the deviations from universality can be a little bit larger compared to the general relativistic case. What is the most interesting in our studies, is that the differences with the pure Einstein’s theory can be large reaching above 20\%. This is qualitative different from the majority of alternative theories of gravity, where the normalized $I$-$Q$ relations are almost indistinguishable from the general relativistic case, and can lead to observational constraints on the $f(R)$ theories in the future.

The chiral phase transition for lattice QCD with 2 colour-sextet quarks

QCD with 2 flavours of massless colour-sextet quarks is studied as a possible walking-Technicolor candidate. We simulate the lattice version of this model at finite temperatures near to the chiral-symmetry restoration transition, to determine whether it is indeed a walking theory (QCD-like with a running coupling which evolves slowly over an appreciable range of length scales) or if it has an infrared fixed point, making it a conformal field theory. The lattice spacing at this transition is decreased towards zero by increasing the number $N_t$ of lattice sites in the temporal direction. Our simulations are performed at $N_t=4,6,8,12$, on lattices with spatial extent much larger than the temporal extent. A range of small fermion masses is chosen to make predictions for the chiral (zero mass) limit. We find that the bare lattice coupling does decrease as the lattice spacing is decreased. However, it decreases more slowly than would be predicted by asymptotic freedom. We discuss whether this means that the coupling is approaching a finite value as lattice $N_t$ is increased — the conformal option, or if the apparent disagreement with the scaling predicted by asymptotic freedom is because the lattice coupling is a poor expansion parameter, and the theory walks. Currently, evidence favours QCD with 2 colour-sextet quarks being a conformal field theory. Other potential sources of disagreement with the walking hypothesis are also discussed. We also report an estimate of the position of the deconfinement transition for $N_t=12$, needed for choosing parameters for zero-temperature simulations.

Equations of state in the Hartle-Thorne model of neutron stars selecting acceptable variants of the resonant switch model of twin HF QPOs in the atoll source 4U 1636-53

The Resonant Switch (RS) model of twin high-frequency quasi-periodic oscillations (HF QPOs) observed in neutron star binary systems, based on switch of the twin oscillations at a resonant point, has been applied to the atoll source 4U 1636-53 under assumption that the neutron star exterior can be approximated by the Kerr geometry. Strong restrictions of the neutron star parameters M (mass) and a (spin) arise due to fitting the frequency pairs admitted by the RS model to the observed data in the regions related to the resonant points. The most precise variants of the RS model are those combining the relativistic precession frequency relations with their modifications. Here, the neutron star mass and spin estimates given by the RS model are confronted with a variety of equations of state (EoS) governing structure of neutron stars in the framework of the Hartle-Thorne theory of rotating neutron stars applied for the observationally given rotation frequency f_rot~580 Hz (or alternatively f_rot~290 Hz) of the neutron star at 4U 1636-53. It is shown that only two variants of the RS model based on the Kerr approximation are compatible with two EoS applied in the Hartle-Thorne theory for f_rot~580 Hz, while no variant of the RS model is compatible for f_rot~290 Hz. The two compatible variants of the RS model are those giving the best fits of the observational data. However, a self-consistency test by fitting the observational data to the RS model with oscillation frequencies governed by the Hartle-Thorne geometry described by three spacetime parameters M, a and (quadrupole moment) q related by the two available EoS puts strong restrictions. The test admits only one variant of the RS model of twin HF QPOs for the Hartle-Thorne theory with the Gandolfi et al. (2010) EoS predicting the parameters of the neutron star $M \sim 2.10 \mathrm{M}_{\odot}$, $a \sim 0.208$, and $q/a^2 \sim 1.77$.

Vacuum condensates as a mechanism of spontaneous supersymmetry breaking

A possible mechanism for the spontaneous breaking of SUSY, based on the presence of vacuum condensates, is reviewed. Such a mechanism could occur in many physical examples, both at the fundamental and emergent level, and would be formally analogous to spontaneous SUSY breaking at finite temperature in the TFD formalism, in which case it can be applied as well. A possible experimental setup for detecting such a breaking through measurement of the Anandan-Aharonov invariants associated with vacuum condensates in an optical lattice model is proposed.

Simulator of Galaxy Millimeter/Submillimeter Emission (SIGAME): The [CII]-SFR Relationship of Massive z=2 Main Sequence Galaxies

We present SIGAME simulations of the [CII] 157.7 {\mu}m fine structure line emission from cosmological smoothed particle hydrodynamics (SPH) simulations of main sequence galaxies at z = 2. Using sub-grid physics prescriptions the gas in our galaxy simulations is modelled as a multi-phased interstellar medium (ISM) comprised of molecular gas residing in the inner regions of giant molecular clouds, an atomic gas phase associated with photodissociation regions at the surface of the clouds, and a diffuse, fully ionized gas phase. Adopting a density profile of the clouds and taking into account heating by the local FUV radiation field and cosmic rays – both scaled by the local star formation rate density – we calculate the [CII] emission from each of the aforementioned ISM phases using a large velocity gradient approach for each cloud, on resolved and global scales. The [CII] emission peaks in the central (<~ 1 kpc) regions of our galaxies where the star formation is most intense, and we find that the majority (>~ 60%) of the emission in this region originates in the molecular gas phase. At larger galactocentric distances (>~2 kpc), the atomic gas is the main contributor to the [CII] emission (>~ 80%), and at all radii the ionized gas provides a negligible amount (<~ 5%) to the [CII] budget. Our simulations predict a log-linear relationship between the integrated [CII] luminosity and star formation rate with a slope (0.80 +/- 0.12) in agreement with observationally determined slopes (~ 0.85 – 1.00) but with a ~ 3 times higher normalization than the observed z ~ 0 relation.

 

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