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Showing 1 - 25 of 25.
Anonymous (not verified) Supercomputation applied to Nuclear Physics Assumpta Parreño Universitat de Barcelona assum@fqa.ub.edu The dynamics of matter in high energy processes can be studied by using the analytic techniques of quantum field theory. Unfortunately, the complicated quark-gluon dynamics precludes the analytic calculation of low-energy nuclear reactions, as well as the nuclear structure, directly from the underlying theory of the strong interaction, QCD. During this talk, I will explain how we use supercomputers to calculate strong interaction processes relevant for nuclear physics. I will describe the numerical technique of Lattice QCD, which uses a four-dimensional lattice containing as degrees of freedom the basic building blocks of matter, quarks and gluons, and I will update you on our recent achievements in the field.
Anonymous (not verified) Pealing off layers of data contamination when measuring the 3D galaxy power spectrum Benedict Kalus ICCUB benedict.kalus@icc.ub.edu I consider techniques to remove contaminants when calculating the 3D galaxy power spectrum. The commonly used naïve template subtraction technique estimates the power spectrum quickly but in a biased way. The mode deprojection scheme is designed to give an unbiased power spectrum, but it requires huge costly matrix operations. Prior to normalisation, template subtraction and mode deprojection yield identical results. I, therefore, argue that one can remove contaminants from the 3D galaxy power spectrum using template subtraction, and then remove the bias either using the normalisation of
the quadratic maximum likelihood (QML) estimator as one would do for mode deprojection, or to use a new and computationally cheaper method that is an extension to the FKP estimator and also debases the power
spectrum estimate, but slightly increases the error bars by not weighting each mode optimally. However, the increase of the error is small in the test cases that we analyse and is less severe than many
other sub-optimal assumptions commonly employed. I show how this can be applied to the systematic contaminants in BOSS galaxy data.
Anonymous (not verified) Type Ia Supernovae: The Search for the Progenitors Carles Badenes University of Pittsburgh / ICCUB badenes@pitt.edu Type Ia Supernovae are still the best standard candles for the measurement of cosmological distances, but the precise nature of their stellar progenitors remains a mystery. While we are reasonably sure that the exploding star is a white dwarf composed of carbon and oxygen, the mechanism by which this star becomes unstable and explodes has never been established. I will review the current observational evidence on Type Ia SN progenitors, the challenges in this field, and a few recent advances.
Anonymous (not verified) Core-crust transition and crustal properties in neutron stars Claudia Gonzalez Boquera University of Barcelona, ICCUB claugb@fqa.ub.edu An accurate determination of the core-crust transition is necessary in the modelling of neutron
stars for astrophysical purposes. The properties of the core-crust transition are
intimately related to the isospin dependence of the nuclear force at low baryon densities.
We obtain the core-crust transition density, asymmetry and pressure
by studying the thermodynamical stability of the core.
Next, we analyze the correlation of these transition properties with the
slope of the symmetry energy associated to the nuclear equation of state.
Finally, we integrate the Tolman-Oppenheimer-Volkov equations in order to
obtain the relation between the neutron star masses and radii.
Knowing the core-crust transition point,
we are also able to predict the mass, thickness and moment of inertia of the neutron star crust.
Anonymous (not verified) prova esther esther ICCUB estpallgui@icc.ub.edu Hola que tal
Anonymous (not verified) Gravitational waves and the nature of spacetime Gustavo E. Romero IAR, CONICET gustavo.esteban.romero@gmail.com Gravitational waves are a natural prediction of General Relativity. The direct detection of these waves has been a major confirmation that the theory can make accurate predictions in the strong gravity regime. In this talk I will review some of the implications of this discovery for the hypothesis that spacetime is a real entity.
Anonymous (not verified) Gaia astrometric instrument calibration and image processing Javier Castañeda ICCUB jcastapo@fqa.ub.edu Gaia is an extremely ambitious astrometric space mission. It aims to measure with very high accuracy the positions, motions and parallaxes of a large number of stars and galactic objects, including also for almost all the objects information about their brightness, colour, radial velocity, orbits and astrophysical parameters. Gaia requires a demanding data processing system on both data volume and processing power. The treatment of the Gaia data has been designed as an iterative process between several systems each one solving different aspects of the data reduction system. In this talk I will explain one of the instrument calibration and astrometric data processing system more demanding in data volume and processing power. The design and implementation of this system presents several challenges; covering not only the purely scientific problems that appear in any data reduction but also the technical issues for the processing of the huge amount of data that Gaia is providing. The design has also been driven by the characteristics and restrictions of the execution environment and resources -- Marenostrum supercomputer hosted by the Barcelona Supercomputing Center (BSC) (Spain).
Anonymous (not verified) TBD Lluis Mas Ribas University of Oslo lluismasribas@gmail.com TBD
Anonymous (not verified) The Connection Between Galaxies and the Intergalactic Medium Lluis Mas Ribas University of Oslo lluismasribas@gmail.com The evolution of galaxies and the large-scale intergalactic medium go hand in hand due to their interaction, which takes place in a region around galaxies called circumgalactic medium. I will present new approaches for probing this region, and how we can extract valuable information from it to reveal some cosmic properties across the history of our Universe.
Anonymous (not verified) Entanglement and squeezing of one and two impurities in a BEC M.A. García-March ICFO – Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, 08860 Castelldefels (Barcelona), Spai garciamarchma@gmail.com Quantum Brownian motion represents a paradigmatic model of complex quantum system. It describes the dynamics of a quantum particle coupled to a bath made up by a huge number of harmonic oscillators. We employ such a model to investigate the physics of one impurity and two distinguishable impurities embedded in a Bose-Einstein condensate (BEC). The case of one particle resembles that of the Bose polaron and has been recently realized in experiments. In an open quantum system context the impurity plays the role of the Brownian particle and the bath is constituted by the Bogoliubov excitations of the condensate. We show that the motion of the impurity is described by means of a Langevin quantum equation, with a time non-local damping, i.e. carrying a certain amount of memory effects. We solve this stochastic equation for the case in which the impurity is trapped and the BEC is homogeneous. We find genuine position squeezing, i.e. the impurity position variance takes values lower than that imposed by the Heisenberg principle. This effect occurs at low temperatures and is enhanced by the strength of the interactions between the impurity and the BEC. We find the regimes of experimentally realistic parameters in which the model is valid and these effects can be observed. We also study a system of two distinguishable impurities in independent traps embedded in a BEC. We evaluate first how the impurity position variance is affected by the presence of the second impurity. We discuss the entanglement between the two impurities that occurs as a consequence of their independent interaction with the BEC. We detail how this entanglement depends on the distance between their traps, interactions, temperature, trapping frequency etc.
Anonymous (not verified) High and low energy probes for a composite Higgs Marc Riembau IFAE/DESY marc.riembau@desy.de Particle physics is going through a watershed moment. The LHC is exploring directly the TeV scale for the first time, where the true nature of the mechanism that breaks the electroweak symmetry is expected to be unraveled. I'll make a review and show why we think that the Higgs has to be just the tip of the iceberg, and a bigger structure is yet to be discovered. As an example, one of such scenarios may consist of a new strong interaction, the Higgs being a composite state of this sector. I'll present the interplay between high and low energy experiments in order to test this possibility.
Anonymous (not verified) GGD 27 MM1: is it an archetype of an accretion disk around a massive YSO? Nacho Añez Institut de Ciències de l'Espai anyez@ice.csic.es The massive star forming region GGD27(IRAS -181622048) is located at a distance of 1.7Kpc. It shows the spectacular and highly collimated radio jet known, HH 80-81-80N, with is powered by a massive (early B-type) protostar. We have found for first time evidences of the presence of an accretion disk surrounding the massive protostar, through (sub)millimetre high-angular resolution interferometric observations. HH80-81 represents a unique case showing that high-mass protostar form through an accretion disk.
We modeled accretion disk around massive protostar GGD27 MM1 using the irradiated Alpha-acretion disk models with dust settling developed by D’Alession et al. 2006 and updated latter in Osorio et al 2016. In this model the temperature and density structure is calculated self-consistently and the main heating sources are stellar irradiation and viscous dissipation.
By comparing the models with high angular resolution observation at 1.1 mm with ALMA we find a very massive disk, what could mean that relationship between stellar and disk mass is different in massive stars.
We found significant substructure in the disk. Here, we compare these substructures with the ones found in low mass disks.
Anonymous (not verified) Primordial Black Holes in Cosmology Nicola Bellomo ICCUB nicola.bellomo@icc.ub.edu The model in which Primordial Black Holes (PBHs) constitute a non-negligible fraction of the dark matter has (re)gained popularity after the first detections of binary black hole mergers. Most of the observational constraints to date have been derived assuming a single mass for all the PBHs, although some more recent works tried to generalize constraints
to the case of extended mass distributions (EMD). In this talk we present a general methodology to obtain constraints for any PBHs EMD and any observables in the desired mass range, starting from those obtained for a monochromatic distribution. We apply this methodology to the study of PBHs effects on the cosmic microwave background in order to put constraints on the fraction of dark matter in PBHs, not only for monochromatic PBH mass distributions but also for popular EMD. Finally we present a way to discriminate if BHs progenitors has primordial or stellar origin by using galaxy surveys.
Anonymous (not verified) A new model for realistic 3-D simulations of solar energetic particle events Nicolas Wijsen KU Leuven Nicolas.wijsen@kuleuven.be The Sun is a highly dynamical object, producing energetic phenomena like bright solar flares and violent eruptions called coronal mass ejections (CMEs). During these eruptions, the Sun hurls a billion-ton cloud of charged particles into space. There is a consensus in the Heliophysics community that CMEs play a leading role in governing the Sun-Earth System (SES) as a consequence of their direct interaction with the space environment near the Earth. As CMEs evolve in the solar corona and interplanetary space, they drive shock waves which act as powerful accelerators of charged particles in the inner solar system. These particles, known as solar energetic particles (SEPs), can strike our planet where they may disrupt satellites and endanger human life in outer space. That is why it is important to understand and predict the ever-changing environmental conditions in outer space due to solar storms – the Space Weather.

A physics-based model for predicting shock-accelerated energetic particles requires a realistic inner heliospheric model for the solar wind and the evolution of CMEs. In view of this, Dr. Jens Pomoell (Univ. of Helsinki) recently developed EUHFORIA (‘European heliospheric forecasting information asset’). This numerical model consists of 1) a semi-empirical coronal model driven by observations of the photospheric magnetic field and 2) an advanced MHD code from 0.1 au onwards to accurately capture the time-dependent three-dimensional evolution of the solar wind plasma in the inner heliosphere.

For reliable SEP modelling one needs not only a heliospheric model for the solar wind and the evolution of CMEs, but also a particle transport code. The propagation of SEPs in the heliosphere can be described by the so-called focused transport equation. One way to solve this five-dimensional parabolic partial differential equation is by integrating a set of corresponding first order Itô stochastic differential equations. In doing so, one can obtain the SEP distributions in interplanetary space.

This talk will consist of three parts. In the first part, we will introduce the solar eruptive events that are thought to be the main accelerators of SEPs. In the next part, we will show how these events can be modelled using the EUHFORIA model. Finally, in the last part of the talk, we will discuss how we can model the transport of SEPs in the heliosphere, once they escaped their acceleration site.
Anonymous (not verified) Mass-loading and non-thermal emission from AGN jets interacting with stellar populations Núria Torres-Albà Universitat de Barcelona (ICCUB) ntorres@fqa.ub.edu
Supermassive blackholes, present in the innermost regions of galaxies, may accrete the material surrounding them, becoming AGN. Some AGN produce jets, which propagate through the complex environment characteristic of the central regions of the host galaxy. This may lead to the jet interacting with a variety of obstacles; including stars, gas and dense clouds. These interactions may affect the jet dynamically, mass-loading and even decelerating it. In addition, when the jet collides with the obstacles, a shock is formed in which particles can be accelerated to relativistic speeds, emitting non-thermal high-energy radiation, potentially detectable for nearby sources.
Anonymous (not verified) Astrophysics with The Evryscopes: the first simultaneous all-sky high-cadence survey Octavi Fors ICCUB / University of North Carolina at Chapel Hill octavi.fors@gmail.com The Evryscope is a unique type of telescopes array which monitors the entire accessible sky in each exposure. The system, with 700 MPix covering an 8000-square-degree field of view, is building many-year-length, two-minute cadence light curves for every accessible object down to g'∼16mag.
This opens a new parameter space in time-domain astronomy, trading instantaneous depth and sky sampling (~13"/pixel) for continuous coverage (97% survey time efficiency) of the largest sky area of any active survey.
The photometric performance g'~10mag is 1%-level precision, and improves to 6 mmags when 30-minute binning is applied.
The resulting data products span multiple science cases, e.g., detection of transiting exoplanets in multiple host star vs. planet configuration, census of stellar activity by flares detection, planetary microlensing events, exoplanets detection by precision timing of eclising binaries, nearby extragalactic transients (SNs, GRBs), and a wide range of other short timescale events (accreting compact objects, exotic pulsators, FRBs, optical GW counterparts).
The Evryscope-South at CTIO was deployed in May 2015 and has already collected 250TB of raw data, 14 millions light curves in DB with ~4x10^11 photometric measurements.
A second identical system is under completion for deployment at Mount Laguna Observatory in California in Spring 2018. Both systems will be provided with r' and g' filters, so that simultaneous two-color photometry over the 4000 square degree overlapping region or single-color all-sky photometry will be possible, operating as a combined discovery and follow-up network for transient phenomena on all nearby stars and many nearby galaxies.

I will present the status of current Evryscope system, the big-data analysis required to explore the petabyte-scale data set we are collecting over the next few years, and the first science results.
Anonymous (not verified) The Star Formation Rate of Molecular Clouds Paolo Padoan ICC & ICREA ppadoan@icc.ub.edu We compute the star formation rate (SFR) in molecular clouds (MCs) that originate ab initio in a high-resolution simulation of supernova-driven turbulence. Because of the large number of well-resolved clouds with self-consistent boundary and initial conditions, we obtain a large range of cloud physical parameters with realistic statistical distributions, an unprecedented sample of star-forming regions to test SFR models and to interpret observational surveys. We confirm the dependence of the SFR per free-fall time, SFRff, on the virial parameter, αvir, found in previous simulations, and compare a revised version of our turbulent fragmentation model with the numerical results. The dependences on Mach number, gas to magnetic pressure ratio and compressive to solenoidal power ratio at fixed αvir are not well constrained, because of random scatter due to time and cloud-to-cloud variations in SFRff. We find that SFRff in MCs can take any value in the range 0-0.2, and its probability distribution peaks at a value SFRff~0.025, consistent with observations. The values of SFRff and the scatter in the SFRff-αvir relation are consistent with recent measurements in nearby MCs and in clouds near the Galactic center.
Anonymous (not verified) Flavour Anomalies Pere Arnan ICCUB arnan@icc.ub.edu Recent measurements of $b\to s\mu^+\mu^-$ processes at LHCb and BELLE have revealed tensions at 2-3$\sigma$ level between the Standard Model (SM) prediction and the experimental results. There are also measurements of $b\to s\tau\nu$ processes with a tension up to 4$\sigma$ respect to the SM, Combined global fits to the available data suggest that these tensions might have their common origin in New Physics (NP) beyond the SM. These tensions are known as the Flavour Anomalies.

In this talk, I review some of the observables which are in tension with the SM, discussing which ones are better to work with due to their cleanliness. I also mention NP models such as $Z',W'$ models, leptoquarks, or models with new scalars and fermions that try to solve these tensions between the SM and the experiment.
Anonymous (not verified) Winds and Jets from the Lighthouse Nebula Pol Bordas ICCUB pbordas@fqa.ub.edu The Lighthouse Nebula is powered by an ultra-fast runaway pulsar, IGR J11014-6103, which is traveling through the interstellar medium at a velocity greater than 1000 km/s. Deep observations of the Nebula with the Chandra satellite have revealed the presence of jet-like structures extending for more than 10 psc, becoming the longest jets ever seen in the Galaxy. A classical jet scenario cannot account however for the observed unbending of these linear structures, nor for its spectral properties. In this talk, I will review the observational data available on the source and the different scenarios proposed to explain its morphology, including the escape of high-energy particles from the pulsar bow-shock and their diffusion into the interstellar magnetic field.
Anonymous (not verified) The usage of photon detectors at ICCUB research Ricardo Graciani ICCUB/Universitat de Barcelona graciani@fqa.ub.edu The usage of photon detectors, and its associated electronics, at different research projects participated by ICCUB will be summarised. A previous introduction to the different families of photon detectors, their operation principles and main characteristic will also be reviewed.
Anonymous (not verified) News on the structure and evolution of our Galaxy from stellar kinematics Teresa Antoja ICCUB tantoja@fqa.ub.edu I will explain some recent discoveries about our Galaxy coming from measurements of the stellar kinematics. We have gathered kinematic data for stars located in a relatively small volume around the Sun coming from the RAVE survey and from the first Gaia data release. With these data, we have been able to determine the pattern speed of the central bar of the Galaxy, to discover the unexpected effects of the bar on the thick disk, and to measure asymmetries that may be related to the orbital effects of the spiral arms.
Anonymous (not verified) Breaking of Translational Invariance in AdS/CFT Tomas Andrade University of Barcelona tandradew@gmail.com Motivated by applications to condensed matter physics, we introduce breaking of translational invariance in the context of AdS/CFT. On the gravity side,
this entails constructing black branes solutions which are not homogeneous along the directions parallel to the brane. We discuss some applications
such as the presence of holographic phonons and the appearance of metal-insulator transitions.
Anonymous (not verified) Open Clusters in the Milky Way with Gaia Tristan Cantat-Gaudin ICCUB tcantat@fqa.ub.edu Open Clusters are convenient tracers of the properties and structure of the Milky Way, because their ages and distances can be estimated more easily than individual stars. The upcoming second data release of the Gaia mission will provide data of unprecedented quality for more than a billion stars, enabling us to better characterise stellar clusters and to discover new ones, providing more insight on the history and structure of our Galaxy.
Anonymous (not verified) Holographic collisions near a critical point Yago Bea Besada Universitat de Barcelona yago.bea.b@gmail.com The phase diagram of quantum chromodynamics (QCD) at finite temperature and chemical potential remains largely unknown. There is certain theoretical evidence for the existence of a critical point in this phase diagram, and currently there are ongoing heavy ion collision experiments devoted to its search. From a theoretical point of view, the study of the critical point physics is very limited, because perturbative methods or lattice QCD are not applicable. Fortunately, holography is a very useful tool that allows not only to study the equilibrium physics near the critical point, but also out-of-equilibrium physics. Holography was born from string theory in the nineties, and it establishes a duality between quantum field theories and gravity theories. We use holography to model heavy ion collisions in a toy theory with phase transitions of different orders. We obtain qualitative insights that could be a possibility for QCD.