Past Pizza Lunches

Número de entradas: 152

21
Febrero 2020

Intelligent Arxiv: Sort daily papers by learning users topic preferences


Inicio: 12:15h
Ponente: Manuel Szewc (ICAS, ARG)
Lugar: Alberto Lobo Room

We present and discuss some novel applications of the Linear Discriminant Analysis (LDA) technique of Machine Learning (ML). First in the field of New Physics (NP) searches at the LHC, where we are currently applying this unsupervised ML technique to find NP as emerging topics. Motivated by this powerful…
Inicio: 12:15h
Ponente: Manuel Szewc (ICAS, ARG)
Lugar: Alberto Lobo Room

We present and discuss some novel applications of the Linear Discriminant Analysis (LDA) technique of Machine Learning (ML). First in the field of New Physics (NP) searches at the LHC, where we are currently applying this unsupervised ML technique to find NP as emerging topics. Motivated by this powerful tool  we pursued the goal of sorting daily Arxiv papers in given field(s) according to individual user preference.  We model a scientific paper to be built as a combination of different scientific knowledge from diverse topics into a new problem. We apply then the (unsupervised) Machine Learning technique LDA to construct and extract topics from the corpus of papers. We obtain the topic weights of the available and new papers in the Arxiv,  and determine each user preference in topics according to each user preference in papers. This allows to determine the personal preference on new papers according to their topics weight distribution.  We have created the web interface IArxiv.org where users can read personally-sorted daily Arxiv releases (and more) while the algorithm learns his/her preferences.  Yielding therefore a more accurate sorting every day. Current IArxiv.org version runs on categories astro-ph, gr-qc, hep-ph and hep-th.
14
Febrero 2020

The Arp299B-AT1 puzzle: First resolved imaging of a tidal disruption event


Inicio: 12:15h
Ponente: Miguel Pérez Torres (Instituto de Astrofísica de Andalucía (IAA-CSIC))
Lugar: Sala Alberto Lobo (ICE building, Campus UAB)

Tidal disruption events (TDEs) are transient flares produced when a star is ripped apart by the gravitational field of a supermassive black hole (SMBH). While indirect evidence has pointed out that some candidates to being TDEs may have formed a relativistic jet, no direct imaging has confirmed this…
Inicio: 12:15h
Ponente: Miguel Pérez Torres (Instituto de Astrofísica de Andalucía (IAA-CSIC))
Lugar: Sala Alberto Lobo (ICE building, Campus UAB)

Tidal disruption events (TDEs) are transient flares produced when a star is ripped apart by the gravitational field of a supermassive black hole (SMBH). While indirect evidence has pointed out that some candidates to being TDEs may have formed a relativistic jet, no direct imaging has confirmed this hypothesis. I will present the discovery of an energetic nuclear transient in the central regions of the nearby galaxy merger Arp299B. The transient radiated at least 1.5E+52 erg in the infrared but remained elusive at optical and X-ray wavelengths. We interpret its properties to arise from the tidal disruption of a massive (2-6 solar masses) star that passed close to the supermassive black hole. Very-long-baseline interferometry monitoring over a decade shows unambiguous evidence for an evolving jet-like morphology. This is the first case of a confirmed resolved radio jet in a TDE ever, thus validating theoretical predictions. I will briefly discuss the implications of our results in the context of theoretical and observed rates of TDEs, as well as the possible impact of this result in terms of radiative feedback. 
07
Febrero 2020

THE SIZE OF OUR UNIVERSE


Inicio: 12:15h
Ponente: Enrique Gaztañaga
Lugar: Alberto Lobo Room

Cosmic acceleration is telling us that Newton's gravitational law is different from the one we learn in school. I will show how this could imply that our universe is smaller than what we thought. This explains why vacuum energy does not gravitate and can also explain cosmic acceleration without the…
Inicio: 12:15h
Ponente: Enrique Gaztañaga
Lugar: Alberto Lobo Room

Cosmic acceleration is telling us that Newton's gravitational law is different from the one we learn in school. I will show how this could imply that our universe is smaller than what we thought. This explains why vacuum energy does not gravitate and can also explain cosmic acceleration without the need dark energy or modified gravity.
31
Enero 2020

Nuclear activity and star formation in local Luminous Infrared Galaxies


Inicio: 12:15h
Ponente: Rubén Herrero (European Southern Observatory)
Lugar: Sala Alberto Lobo (ICE building, Campus UAB)

Luminous infrared galaxies (LIRGs) dominate the cosmic infrared background, and hence their study is crucial to understand galaxy formation and evolution. Furthermore, their extreme environments make them ideal laboratories to probe both star formation, nuclear activity, and the interplay between both…
Inicio: 12:15h
Ponente: Rubén Herrero (European Southern Observatory)
Lugar: Sala Alberto Lobo (ICE building, Campus UAB)

Luminous infrared galaxies (LIRGs) dominate the cosmic infrared background, and hence their study is crucial to understand galaxy formation and evolution. Furthermore, their extreme environments make them ideal laboratories to probe both star formation, nuclear activity, and the interplay between both phenomena. On this talk I will give an overview on the main physical processes taking place in local LIRGs from a multi-wavelength perspective at different spatial scales, from their overall structure to their central hundred-parsec regions, where extreme processes take place hidden behind the dust.
24
Enero 2020

Electromagnetic counterpart of gravitational wave events


Inicio: 12:15h
Ponente: Nancy Elias Rosa
Lugar: Sala Alberto Lobo (ICE building, Campus UAB)

In the last few years, the gravitational wave (GW) interferometers LIGO and Virgo proved their ability to detect compact mergers and, with the spectacular case of GW 170817. Thanks to them, it is clear that there is a lot to learn from the prompt identification of the electromagnetic counterpart of…
Inicio: 12:15h
Ponente: Nancy Elias Rosa
Lugar: Sala Alberto Lobo (ICE building, Campus UAB)


In the last few years, the gravitational wave (GW) interferometers LIGO and Virgo proved their ability to detect compact mergers and, with the spectacular case of GW 170817. Thanks to them, it is clear that there is a lot to learn from the prompt identification of the electromagnetic counterpart of the GW trigger. This event marked the beginning of a new era for multi-messenger astronomy with a pressing quest for electromagnetic follow up at all wavelengths, particularly in optical bands. During this talk, I will review some of the observations efforts to search and classify possible optical counterparts of GW, including an brief overview of GW 170817.
17
Enero 2020

STARS: Telescope and space mission scheduling towards a multi-observatory framework


Inicio: 12:15h
Ponente: Josep Colomé Ferrer
Lugar: Alberto Lobo Room

Efficient scheduling of astronomical observatories and space missions is a challenge with an increasing complexity as the observation strategies are becoming more sophisticated and operational costs are higher. Astronomical surveys require a huge number of observations, implying the need to use efficient…
Inicio: 12:15h
Ponente: Josep Colomé Ferrer
Lugar: Alberto Lobo Room

Efficient scheduling of astronomical observatories and space missions is a challenge with an increasing complexity as the observation strategies are becoming more sophisticated and operational costs are higher. Astronomical surveys require a huge number of observations, implying the need to use efficient schedulers to fulfill and optimize specific constraints. STARS (Scheduling Telescopes as Autonomous Robotic Systems) is a software suite developed at the institute that provides optimal schedulers for diverse infrastructures, and has been successfully applied in several ground and space-based observatories (TJO, CARMENES, CTA, ARIEL,...). STARS is based on AI algorithms and is extended to cover multi-observatory coordinated scheduling, a challenging and complex optimization problem that will allow an optimal operation of large astrophysical infrastructures to promote multi-messenger science. A light tour through the framework layers will be presented in this talk: from the requirements for different projects to the optimization algorithms used.
10
Enero 2020

White dwarfs as Advanced Physics laboratories: the axion case


Inicio: 12:15h
Ponente: Jordi Isern Vilaboy
Lugar: Alberto Lobo Room

The shape of the luminosity function of white dwarfs (WDLF) is sensitive to the characteristic cooling time and, therefore, it can be used to test the existence of additional sources or sinks of energy such as those predicted by alternative physical theories. However, because of the degeneracy between…
Inicio: 12:15h
Ponente: Jordi Isern Vilaboy
Lugar: Alberto Lobo Room

The shape of the luminosity function of white dwarfs (WDLF) is sensitive to the characteristic cooling time and, therefore, it can be used to test the existence of additional sources or sinks of energy such as those predicted by alternative physical theories. However, because of the degeneracy between the physical properties of white dwarfs and the properties of the Galaxy, the star formation history (SFH) and the IMF, it is almost always possible to explain any anomaly as an artifact introduced by the star formation rate. To circumvent there are at least two possibilities, the analysis of the WDLF in populations with different stories, like disc and halo, and the search of effects not correlated with the SFH. These procedures are illustrated with the case of axions.
17
Diciembre 2019

Especial Christmas Seminar: The 'Climate Emergency': scientific basis, impacts and possible solutions to the first planetary human problem


Inicio: 12:00h
Ponente: Eric Galbraith (Universitat Autònoma de Barcelona (UAB))
Lugar: Alberto Lobo Room

Humanity has been causing environmental problems forever, and has often resolved them with great success. But in the past, these were problems faced by local populations, which were able to coordinate their activities in order to resolve them locally. Climate change is fundamentally different, in that…
Inicio: 12:00h
Ponente: Eric Galbraith (Universitat Autònoma de Barcelona (UAB))
Lugar: Alberto Lobo Room

Humanity has been causing environmental problems forever, and has often resolved them with great success. But in the past, these were problems faced by local populations, which were able to coordinate their activities in order to resolve them locally. Climate change is fundamentally different, in that it is a collective problem played out in the well-mixed global atmosphere, and which can only be addressed through globally-coordinated policy that addresses the majority of our species. Thus far, we have made essentially no tangible progress on this challenge. I will briefly discuss the scientific basis of climate change, including how greenhouse gases work, evidence for natural climate change in the past, and human emissions. I will then review expected impacts of climate change on a range of timescales, focusing on temperatures, food production, sea level rise and ecosystem alterations, as well as the reasons why the impacts will almost certainly exceed expectations. I will then discuss the possible means by which climate change can be mitigated or reversed, and how these might interact with other aspects of human activities and well-being. I will conclude that, although a daunting challenge, the climate emergency may provide the impetus required to develop global policy that could benefit humanity in the long-term.
13
Diciembre 2019

ELGAR: The European Laboratory for Gravitation and Atom-interferometric Research


Inicio: 12:15h
Ponente: Carlos Sopuerta (ICE)
Lugar: Alberto Lobo Conference Room

After the inauguration of Gravitational Wave Astronomy with the first direct detection of Gravitational Waves from a binary black hole coalescence by the Laser Interferometer Gravitational-wave Observatory (LIGO), the race to cover the most relevant parts of the Gravitational-wave spectrum is currently…
Inicio: 12:15h
Ponente: Carlos Sopuerta (ICE)
Lugar: Alberto Lobo Conference Room

After the inauguration of Gravitational Wave Astronomy with
the first direct detection of Gravitational Waves from a binary black
hole coalescence by the Laser Interferometer Gravitational-wave
Observatory (LIGO), the race to cover the most relevant parts of the
Gravitational-wave spectrum is currently at full speed.  Indeed, after
eleven detections  (10 Binary Black Holes and 1 Binary Neutron Star),
the LIGO-Virgo collaboration, operating in the high-frequency band, is
immersed in the third observation run with a lot of new potential
candidates. On the other hand, LISA is the future ESA-L3 mission for
low-frequency gravitational-wave astronomy. Pulsar Timing Arrays,
covering the very-low frequency band, have sensitivities within the
discovery region of the predicted parameter space. And finally, CMB
polarization experiments continue their developments for the ultra-low
frequency band.

Despite these efforts there are still gaps to fill in the gravitational
wave spectrum.  In particular, the deciHertz band is not well covered
neither by the ground-based detectors nor by LISA. In this talk I will
present new efforts to fill the deciHertz band with a new technology,
atom interferometry, and I will talk about the great science that can be
done with the proposed detector ELGAR.

Reference: http://arxiv.org/abs/1911.03701
29
Noviembre 2019

Black hole in globular clusters


Inicio: 12:15h
Ponente: Mark Gieles
Lugar: Alberto Lobo room

Globular clusters (GCs) are the outcome of the earliest phases of star and galaxy formation in the Universe. Their high densities foster the formation and hardening of binary black holes (BHs) that can merge via gravitational wave in-spiral. The contribution of this `dynamical channel' to gravitational…
Inicio: 12:15h
Ponente: Mark Gieles
Lugar: Alberto Lobo room

Globular clusters (GCs) are the outcome of the earliest phases of star and galaxy formation in the Universe. Their high densities foster the formation and hardening of binary black holes (BHs) that can merge via gravitational wave in-spiral. The contribution of this `dynamical channel' to gravitational wave detections - relative to other channels - is not understood, because it sensitively depends on the poorly constrained BH natal kicks and the unknown properties of infant GCs. I will present results of efforts to infer the BH content of Milky Way GCs by comparing dynamical mass models to kinematics and star counts. We find the signal of a BH population in several Milky Way GCs and I will discuss the implications of these findings for the BH merger rate across cosmic time.
Institute of Space Sciences (IEEC-CSIC)

Campus UAB, Carrer de Can Magrans, s/n
08193 Barcelona.
Phone: +34 93 737 9788
Email: ice@ice.csic.es
Website developed with RhinOS

Síguenos


An institute of the Consejo Superior de Investigaciones Científicas

An institute of the Consejo Superior de Investigaciones Científicas
Affiliated with the Institut d'Estudis Espacials de Catalunya

Affiliated with the Institut d'Estudis Espacials de Catalunya