Past Pizza Lunches

Number of entries: 153

13
April 2018

The Autonomous F(R) Gravity Phase space: From Late-time Evolution to Neutron Stars Dynamics


Start: 12:15h
Speaker: V.K.Oikonomou (Thessaloniki Univ., Greece)
Place: Sala Alberto Lobo (ICE building, Campus UAB)

The f(R) gravity phase space is quite rich in structure, and if correctly constructed it can yield useful information for both astrophysical and cosmological applications. In this work we construct the autonomous dynamical system of vacuum f(R) gravity and we investigate the behavior of the dynamical…
Start: 12:15h
Speaker: V.K.Oikonomou (Thessaloniki Univ., Greece)
Place: Sala Alberto Lobo (ICE building, Campus UAB)

The f(R) gravity phase space is quite rich in structure, and if correctly constructed it can yield useful information for both astrophysical and cosmological applications. In this work we construct the autonomous dynamical system of vacuum f(R) gravity and we investigate the behavior of the dynamical evolution focusing on de Sitter attractors. Also we investigate the case that the late-time attractor develops a Big Rip singularity. As we demonstrate, the late-time attractor is a stable de Sitter attractor which inevitably leads to a Big Rip singularity. We also demonstrate a novel property of the f(R) gravity phase space near Big Rip singularities. For our analysis we employ a powerful theorem that holds true for polynomial autonomous dynamical systems, so the dynamical system must be formed in the above way. Finally, we demonstrate how this theorem can find application in the neutron stars dynamics, and how it can yield useful information for the formation of a singularity at the center of the star.
06
April 2018

Stephen Hawking (1942-2018): The Scientific Legacy


Start: 12:15h
Speaker: Carlos Sopuerta
Place: Sala Alberto Lobo (ICE building, Campus UAB)

In this talk I will try to summarize, from my own personal perspective, the main scientific contributions of Stephen Hawking, taking into account the context of the developments in Relativistic Astrophysics, Cosmology and the quest for a Quantum Theory of Gravitation. 
Start: 12:15h
Speaker: Carlos Sopuerta
Place: Sala Alberto Lobo (ICE building, Campus UAB)

In this talk I will try to summarize, from my own personal perspective, the main scientific contributions of Stephen Hawking, taking into account the context of the developments in Relativistic Astrophysics, Cosmology and the quest for a Quantum Theory of Gravitation. 
23
March 2018

Resolving the polarized dust emission of the disk around the massive star powering the HH~80-81 radio jet


Start: 12:15h
Speaker: Josep Miquel Girart Medina
Place: Work shop room L3-01 (third floor) - But subject to change!

The presence of accretion disks around low mass young stellar objects appears to be ubiquitous. However, it is not clear whther massive stars (M>8Msun) are also formed surrounded by a accretion disks, and if they do, how similar are these disks with respect to the lower mass counterparts.  Here I present…
Start: 12:15h
Speaker: Josep Miquel Girart Medina
Place: Work shop room L3-01 (third floor) - But subject to change!

The presence of accretion disks around low mass young stellar objects appears to be ubiquitous. However, it is not clear whther massive stars (M>8Msun) are also formed surrounded by a accretion disks, and if they do, how similar are these disks with respect to the lower mass counterparts.  Here I present deep (16 μJy beam−1), very high (40 mas) angular resolution 1.14 mm, polarimetric, ALMA observations towards the massive protostar driving the HH 80-81 radio jet (arXiv:1803.06165).  In this talk, I will discuss how polarization can be used a tool to better understand the disk properties, and in particular the disk around the massive star powering the HH~80-81 radio jet.
 
16
March 2018

Unifying interpretation of the high energy spectra of pulsars


Start: 12:15h
Speaker: Diego F. Torres (ICE (CSIC-IEEC))
Place: Alberto Lobo Seminar Room (ICE, UAB Campus)

Pulsars were discovered 50 years ago, after being hypothesized to exist shortly before. We learned a lot about them in these decades, yet critical questions are unanswered. One of the most interesting features of pulsars is their multi-frequency spectral variety. Pulsars that look very similar in one…
Start: 12:15h
Speaker: Diego F. Torres (ICE (CSIC-IEEC))
Place: Alberto Lobo Seminar Room (ICE, UAB Campus)

Pulsars were discovered 50 years ago, after being hypothesized to exist shortly before. We learned a lot about them in these decades, yet critical questions are unanswered. One of the most interesting features of pulsars is their multi-frequency spectral variety. Pulsars that look very similar in one band can be very different in another. For instance, from the hundreds of gamma-ray pulsars known, just a few show non-thermal X-ray pulsations. A few others pulse in X-rays, but lack a high-energy counterpart. Are their emission scenarios the same? What order parameters can be used to describe their spectral variety?
09
March 2018

X-ray reverberation-mapping of the inner flow around accreting black holes


Start: 12:15h
Speaker: Dr. Barbara de Marco (N. Copernicus Astronomical Centre PAN, Warsaw, Poland)
Place: Work shop room L3-01 (third floor)

Strong flux variability is one of the observational manifestations of black hole (BH) accretion. Some of the fastest variations are detected in the X-ray band, where the inner accretion flow is probed. Short time delays are expected between primary X-rays and reprocessed emission in the disc. These “X-ray…
Start: 12:15h
Speaker: Dr. Barbara de Marco (N. Copernicus Astronomical Centre PAN, Warsaw, Poland)
Place: Work shop room L3-01 (third floor)

Strong flux variability is one of the observational manifestations of black hole (BH) accretion. Some of the fastest variations are detected in the X-ray band, where the inner accretion flow is probed. Short time delays are expected between primary X-rays and reprocessed emission in the disc. These “X-ray reverberation lags” map the relative distance between the X-ray source and the accretion disc, therefore they are a powerful tool to map the geometry of the inner regions of the accretion flow. I will review observations of X-ray reverberation in accreting BH systems, and illustrate how such studies with current and upcoming observing facilities can inform our understanding of the structure and dynamics of the accretion flow.
02
March 2018

Pulsars: magnetic monsters, gravitational wave emitters and detectors, and GPS for future deep space travels


Start: 12:15h
Speaker: Nanda Rea (Institute of Space Science (ICE))
Place: L3-01 (Note the change of room for this week only).

Pulsars turned 50 years! Pulsars turned 3000! These relativistic stars are unique laboratories where not only the most extreme gravity and electromagnetism can be probed, but also the strong and weak interaction can be studied in regimes that have no hope of being explored on Earth. The study of these…
Start: 12:15h
Speaker: Nanda Rea (Institute of Space Science (ICE))
Place: L3-01 (Note the change of room for this week only).

Pulsars turned 50 years! Pulsars turned 3000! These relativistic stars are unique laboratories where not only the most extreme gravity and electromagnetism can be probed, but also the strong and weak interaction can be studied in regimes that have no hope of being explored on Earth. The study of these objects transcends the traditional astrophysical approach and requires a multidisciplinary effort that spans from particle and nuclear physics to astrophysics, from gravitational waves to the electromagnetic spectrum, from experiment to theory.
I will review in this talk the most important discoveries in the neutron star field, and what we aim for in the next decade. Particular attention will be given i) to magnetars - the biggest magnets in the Universe, ii) to millisecond pulsars - the fastest rotating astrophysical objects, iii) to pulsars as gravitational wave emitters and detectors, and iv) to pulsars as GPS systems for future deep space travels.
23
February 2018

Beyond General Relativity: exponential gravity as a particular case


Start: 12:15h
Speaker: Diego Sáez-Chillón Gómez (Institute of Space Sciences)
Place: Sala Alberto Lobo

In this talk I will review the basis of some types of modified gravities, their pros and cons and the possibility of reproducing late-time acceleration and their viability. A particular case will be analysed, based on exponential terms in the gravitational action. This type of models may be capable of…
Start: 12:15h
Speaker: Diego Sáez-Chillón Gómez (Institute of Space Sciences)
Place: Sala Alberto Lobo

In this talk I will review the basis of some types of modified gravities, their pros and cons and the possibility of reproducing late-time acceleration and their viability. A particular case will be analysed, based on exponential terms in the gravitational action. This type of models may be capable of reproducing both inflation as the late-time acceleration. I will discuss the constraints coming from different sources of data, both at the inflationary epoch as at late times by using Sne Ia, BAO and Hubble data. As will be shown, exponential gravity may be kept as a promising candidate for dark energy and inflation.
23
February 2018

Pulsars: magnetic monsters, gravitational wave emitters and detectors, and GPS for future space travels


Start: 12:15h
Speaker: Nanda Rea (Institute of Space Science (ICE))
Place: Alberto Lobo room

Pulsars turned 50 years! Pulsars turned 3000! These relativistic stars are unique laboratories where not only the most extreme gravity and electromagnetism can be probed, but also the strong and weak interaction can be studied in regimes that have no hope of being explored on Earth. The study of these…
Start: 12:15h
Speaker: Nanda Rea (Institute of Space Science (ICE))
Place: Alberto Lobo room

Pulsars turned 50 years! Pulsars turned 3000! These relativistic stars are unique laboratories where not only the most extreme gravity and electromagnetism can be probed, but also the strong and weak interaction can be studied in regimes that have no hope of being explored on Earth. The study of these objects transcends the traditional astrophysical approach and requires a multidisciplinary effort that spans from particle and nuclear physics to astrophysics, from gravitational waves to the electromagnetic spectrum, from experiment to theory.
I will review in this talk the most important discoveries in the neutron star field, and what we aim for in the next decade. Particular attention will be given i) to magnetars - the biggest magnets in the Universe, ii) to millisecond pulsars - the fastest rotating astrophysical objects, iii) to pulsars as gravitational wave emitters and detectors, and iv) to pulsars as GPS systems for future deep space travels.
16
February 2018

Communication Signals Used for Remote Sensing


Start: 12:15h
Speaker: Serni Ribó (ICE (CSIC-IEEC))
Place: Alberto Lobo Seminar Room (ICE, UAB Campus)

The Earth is illuminated in the microwave frequency range by hundreds of communication and broadcasting satellites from geostationary orbit. Their potential for remote sensing of the Earth is enormous, as the collective power and frequency range of the transmitted signals surpasses that of earth-observation…
Start: 12:15h
Speaker: Serni Ribó (ICE (CSIC-IEEC))
Place: Alberto Lobo Seminar Room (ICE, UAB Campus)


The Earth is illuminated in the microwave frequency range by hundreds of communication and broadcasting satellites from geostationary orbit. Their potential for remote sensing of the Earth is enormous, as the collective power and frequency range of the transmitted signals surpasses that of earth-observation satellites, and their broad frequency range makes them suitable for atmosphere, land, ocean and cryosphere applications. I will present an overview of the potentialities of such signals for remote sensing and the recent activities we have carried out at our institute.
09
February 2018

Filling up the gaps: on the beginning of modern cosmology


Start: 12:15h
Speaker: Emili Elizalde (ICE-CSIC and IEEC)
Place: Alberto Lobo Room

In this talk, I will give final shape to a number of reflections that I addressed in previous pizza seminars and wich have to do with the origins of modern cosmology. I will provide a list of additional references that have eventually filled up the still existing gaps. I will argue now, in particular,…
Start: 12:15h
Speaker: Emili Elizalde (ICE-CSIC and IEEC)
Place: Alberto Lobo Room


In this talk, I will give final shape to a number of reflections that I addressed in previous pizza seminars and wich have to do with the origins of modern cosmology. I will provide a list of additional references that have eventually filled up the still existing gaps. I will argue now, in particular, in favor of the Year 1912 as the one presumably marking the beginning of modern cosmology, and will present my final conclusions on the actual meaning of the words `Big Bang’. For a written reference of my presentation, see “All That Matter ... in One Big Bang ...,” & Other Cosmological Singularities. arXiv:1801.09550 [physics.hist-ph] 25 Jan 2018 https://arxiv.org/pdf/1801.09550.pdf; Preprints 2018, 2018010251 (doi: 10.20944/preprints201801.0251.v1). Elizalde, E. https://www.preprints.org/manuscript/201801.0251/v1
 
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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