Past Pizza Lunches

Number of entries: 152

20
November 2020

From a Bounce to the Dark Energy Era with F(R) Gravity


Start: 12:15h
Speaker: Prof. Tanmoy, P.
Place: https://us02web.zoom.us/j/85044910172?pwd=bXRmeWx3cTdDSzkrMFFJUXI5eE9hQT09

In this work we consider a cosmological scenario in which the Universe contracts initially having a bouncing-like behavior, and accordingly after it bounces off, it decelerates following a matter dominated like evolution and at very large positive times it undergoes through an accelerating stage. Our…
Start: 12:15h
Speaker: Prof. Tanmoy, P.
Place: https://us02web.zoom.us/j/85044910172?pwd=bXRmeWx3cTdDSzkrMFFJUXI5eE9hQT09

In this work we consider a cosmological scenario in which the Universe contracts initially having a bouncing-like behavior, and accordingly after it bounces off, it decelerates following a matter dominated like evolution and at very large positive times it undergoes through an accelerating stage. Our aim is to study such evolution in the context of F(R) gravity theory, and confront quantitatively the model with the recent observations. Using several reconstruction techniques, we analytically obtain the form of F(R) gravity in two extreme stages of the universe, particularly near the bounce and at the late time era respectively. With such analytic results and in addition by employing appropriate boundary conditions, we numerically solve the F (R) gravitational equation to determine the form of the F (R) for a wide range of values of the cosmic time. The numerically solved F (R) gravity realizes an unification of certain cosmological epochs of the universe, in particular, from a non-singular bounce to a matter dominated epoch and from the matter dominated to a late time dark energy epoch. Correspondingly, we calculate the scalar and tensor perturbations power spectra near the bouncing point, and accordingly we determine the observable quantities like the spectral index of the scalar curvature perturbations, the tensor-to-scalar ratio, and as a result, we directly confront the present model with the latest Planck observations. Furthermore the F (R) gravity dark energy epoch is confronted with the Sne-Ia+BAO+H(z)+CMB data.
13
November 2020

Neutron Stars - Cosmic Superfluids and Superconductors


Start: 12:15h
Speaker: Vanessa Graber (ICE)
Place: Zoom: https://us02web.zoom.us/j/85044910172?pwd=bXRmeWx3cTdDSzkrMFFJUXI5eE9hQT09 Meeting ID: 850 4491 0172 Passcode: 996691

Neutron stars unite many extremes of physics which cannot be recreated on Earth, making them excellent cosmic laboratories to study dense matter. One exciting characteristic is the presence of superfluid and superconducting components in mature neutron stars; macroscopic quantum behaviour that exhibits…
Start: 12:15h
Speaker: Vanessa Graber (ICE)
Place: Zoom: https://us02web.zoom.us/j/85044910172?pwd=bXRmeWx3cTdDSzkrMFFJUXI5eE9hQT09 Meeting ID: 850 4491 0172 Passcode: 996691

Neutron stars unite many extremes of physics which cannot be recreated on Earth, making them excellent cosmic laboratories to study dense matter. One exciting characteristic is the presence of superfluid and superconducting components in mature neutron stars; macroscopic quantum behaviour that exhibits many similarities to terrestrial systems such as superfluid phases in ultra-cold atomic gases, heavy-ion collisions or superconducting transitions in metals. Although many theoretical models of superfluid and superconducting neutron stars have benefited from our understanding of laboratory condensates, several directions in connecting neutron star astrophysics and low-temperature physics remain little explored. In this talk, I will provide an overview of what we know about superfluid and superconducting neutron star components, and specifically focus on two aspects, pulsar spin-glitches and core superconductivity, where the link to laboratory quantum systems can help us improve our understanding of neutron stars.
06
November 2020

The Nüwa project - a Martian city that can sustain its own growth


Start: 12:15h
Speaker: Guillem Anglada Escude (ICE)
Place: https://us02web.zoom.us/j/85044910172?pwd=bXRmeWx3cTdDSzkrMFFJUXI5eE9hQT09

Is it possible to build a human settlement that can sustain its own growth? With the sight put into developing a long term and sustainable presence of human activities in space, a very fundamental question that needs to be addressed is whether a human settlement can be developed and self-sustain on another…
Start: 12:15h
Speaker: Guillem Anglada Escude (ICE)
Place: https://us02web.zoom.us/j/85044910172?pwd=bXRmeWx3cTdDSzkrMFFJUXI5eE9hQT09

Is it possible to build a human settlement that can sustain its own growth? With the sight put into developing a long term and sustainable presence of human activities in space, a very fundamental question that needs to be addressed is whether a human settlement can be developed and self-sustain on another planet. Despite there seems to be no physical barriers to achieve it, it is unclear if all the material cycles and be closed to the required level and if the amount of workload the average human should endure is manageable. To start a conversation on this topic, The Sustainable Offworld Netword (SONet) performed a design exercise to answer a call along this lines issed by the Mars Society. We proceeded in an engineering desing way listing functions, identifying requirements, and drafting solutions to cover both technical and socio-economic aspects in a multi-disciplinary collaboration. I will present you a summary of the findings, the 'costs' in terms of materials and resources, and discuss its feasibility with our current technological level.
30
October 2020

The neutron star population in our Galaxy


Start: 12:15h
Speaker: Nanda Rea ((ICE-CSIC, IEEC))
Place: Zoom: https://us02web.zoom.us/j/85044910172?pwd=bXRmeWx3cTdDSzkrMFFJUXI5eE9hQT09 Meeting ID: 850 4491 0172 Passcode: 996691

I will review the group research activity of the past months, focusing on the recent detection of two interesting new highly magnetic neutron stars in our Galaxy. I will finish with some preliminary studies on the comparison of our neutron star population, with the Universe most extreme events such as…
Start: 12:15h
Speaker: Nanda Rea ((ICE-CSIC, IEEC))
Place: Zoom: https://us02web.zoom.us/j/85044910172?pwd=bXRmeWx3cTdDSzkrMFFJUXI5eE9hQT09 Meeting ID: 850 4491 0172 Passcode: 996691

I will review the group research activity of the past months, focusing on the recent detection of two interesting new highly magnetic neutron stars in our Galaxy. I will finish with some preliminary studies on the comparison of our neutron star population, with the Universe most extreme events such as Gamma Ray Bursts and Fast Radio Bursts.
23
October 2020

Physics Nobel Prize 2020: Black Hole Formation and the Supermassive Black Hole at the Milky Way Galactic Center


Start: 12:15h
Speaker: Carlos Sopuerta (ICE, CSIC and IEEC)
Place: Zoom Meeting: https://us02web.zoom.us/j/85044910172?pwd=bXRmeWx3cTdDSzkrMFFJUXI5eE9hQT09 Meeting ID: 850 4491 0172 Passcode: 996691

The Black Hole idea is a purely relativistic concept: Contrary to stars, which humans see with their own eyes and are in the process of understanding what are they made of and where they come from, the Black Hole concept emerges from the General Theory of Relativity that Albert Einstein completed in…
Start: 12:15h
Speaker: Carlos Sopuerta (ICE, CSIC and IEEC)
Place: Zoom Meeting: https://us02web.zoom.us/j/85044910172?pwd=bXRmeWx3cTdDSzkrMFFJUXI5eE9hQT09 Meeting ID: 850 4491 0172 Passcode: 996691

The Black Hole idea is a purely relativistic concept: Contrary to stars, which humans see with their own eyes and are in the process of understanding what are they made of and where they come from, the Black Hole concept emerges from the General Theory of Relativity that Albert Einstein completed in 1915. The Black Hole concept is also a geometrical concept in the sense that their composition is irrelevant. Moreover, the Black Hole concept is revolutionary: Despite Karl Schwarzschild found the first Black Hole model in 1916 it was not until the late 1950s that we understood their nature. 

Roger Penrose pioneered in the 1970s a new way of studying General Relativity, with new methods and techniques, that clarified the fact that Black Holes are not just weird solutions of the theory but the unavoidable consequence of gravitational collapse and therefore they must be ubiquitous objects in our Universe. On the other hand, the most convincing observational evidence of the existence of Black Holes (left alone the recent observations by the LIGO gravitational wave detector that already got the Nobel Prize) comes from the observations of the Galactic Center made since the early 1990s by the research groups led by Reinhard Genzel and Andrea Ghez. By monitoring stars orbiting the region of Sagittarius A* they concluded that there must be a supermassive black hole pulling those stars into such orbits. And this is the most conservative explanation that we have for this system.
26
June 2020

Rectifying Problematic Modified Gravity Theories in View of GW170817


Start: 12:15h
Speaker: V.K.Oikonomou (Thessaloniki Univ., Greece )
Place: Remote Pizza Seminar

The striking event GW170817 indicated that gravitons are nearly massless, since the gravitational waves and the gamma rays emitted from the two neutron stars merging arrived almost simultaneously. Since there is no fundamental reason for the graviton to change its mass during the inflationary and…
Start: 12:15h
Speaker: V.K.Oikonomou (Thessaloniki Univ., Greece )
Place: Remote Pizza Seminar

The striking event GW170817 indicated that gravitons are nearly massless, since the gravitational waves and the gamma rays emitted from the two neutron stars merging arrived almost simultaneously. Since there is no fundamental reason for the graviton to change its mass during the inflationary and post-inflationary era, several modified gravities predicting a primordial gravity wave speed not equal to that of light, became non-viable. In this talk we shall demonstrate how Einstein-Gauss-Bonnet theories and some classes of Hondeski theories may be revived in view of the GW170817, thus predicting a nearly zero mass for the primordial graviton.
19
June 2020

ETG properties as revealed by MaNGA


Start: 12:15h
Speaker: Helena Domínguez Sánchez (Institut de Ciències de l'Espai (CSIC-IEEC))
Place: Remote Pizza Seminar

In this talk I will (try to!) summarise the findings presented in a series of four papers dedicated to the study of early type galaxies (ETGs) with integral field spectroscopy (IFU) from the MaNGA survey. The formation channels and mass assembly of ETGs is still a matter of debate in current galaxy evolution…
Start: 12:15h
Speaker: Helena Domínguez Sánchez (Institut de Ciències de l'Espai (CSIC-IEEC))
Place: Remote Pizza Seminar

In this talk I will (try to!) summarise the findings presented in a series of four papers dedicated to the study of early type galaxies (ETGs) with integral field spectroscopy (IFU) from the MaNGA survey. The formation channels and mass assembly of ETGs is still a matter of debate in current galaxy evolution models. The combined analysis of galaxy kinematics and stellar population gradients (age, metallicity, alpha-enhancement, initial mass function -IMF-) is a powerful tool to disentangle  between in situ star formation or merger events. We divide our sample into elliptical fast rotators (E-FR), elliptical slow rotators (E-SR) and lenticular (S0). To achieve enough signal to noise to reliably measure IMF variations we need to stack the galaxies in bins of luminosity and central velocity dispersion. We observe significant differences between the three sub-samples — e.g., E-FR are much younger and metal rich than E-SR — , suggesting that kinematics and morphology have a strong impact on galaxy content. In addition, I will show that there are three mass-scales where scaling relations change slope and for which there is also a dramatic change in the number counts and stellar population gradients of ETGs. I will also discuss the implications of IMF variations within galaxies and how this helps reconciling stellar mass with dynamical mass estimates. Finally, I will show that the thickness of the Fundamental Plane depends strongly on morphology. If the sample only includes E-SRs, then the observed scatter is significantly reduced.
05
June 2020

The Driving Mechanisms Of Protostellar Evolution


Start: 12:15h
Speaker: Felipe Alves (Center for Astrochemical Studies, Max-Planck-Institut für extraterrestrische Physik)
Place: Remote Pizza Seminar

Gravity and magnetic fields are competing entities in the formation process of stars like our Sun. While dense cores of molecular clouds collapse under their own gravity, magnetic fields represent a resisting force since charged dust and gas are tied to the field lines. Polarization observations have…
Start: 12:15h
Speaker: Felipe Alves (Center for Astrochemical Studies, Max-Planck-Institut für extraterrestrische Physik)
Place: Remote Pizza Seminar

Gravity and magnetic fields are competing entities in the formation process of stars like our Sun. While dense cores of molecular clouds collapse under their own gravity, magnetic fields represent a resisting force since charged dust and gas are tied to the field lines. Polarization observations have shown that magnetic fields are unambiguously present in the universe and theory predicts their severe impact on the core dynamics. Because the new generation of instruments such as ALMA and SOFIA has been revealing the magnetic field morphology, dust and gas distribution in cores and protostellar cocoons in great detail, we have expanded our understanding of the interplay between magnetic fields and gravity. In this talk, I will review some of the classical and modern aspects of protostellar evolution, and present my contribution to the topic. Specifically, I will focus on our ALMA observations toward one of the nearest regions of low-mass star-forming regions, Barnard 59. 
24
April 2020

The Atacama Large Aperture Submm Telescope (AtLAST): Cosmological and Sunyaev-Zeldovich Effect Applications


Start: 12:15h
Speaker: Tony Mroczkowski (European Southern Observatory )
Place: Remote Pizza Seminar

The thermal and kinematic SZ effects provide a strong and independent complement to X-ray observations of the warm and hot ionised intracluster medium, particularly at high redshift where X-ray counts are limited. Being observable from the ground, new instruments for studying the SZ effects can be developed…
Start: 12:15h
Speaker: Tony Mroczkowski (European Southern Observatory )
Place: Remote Pizza Seminar

The thermal and kinematic SZ effects provide a strong and independent complement to X-ray observations of the warm and hot ionised intracluster medium, particularly at high redshift where X-ray counts are limited. Being observable from the ground, new instruments for studying the SZ effects can be developed more rapidly and can be upgraded more readily than their space-borne counterparts. I will discuss recent results from ALMA and MUSTANG2, as well as a newly-proposed research infrastructure (recently approved by the European Commission as a Design Study) for a 50-meter-class widefield submm/mm telescope called AtLAST. AtLAST will be capable of observing the multifaceted SZ effects and disentangling them from contaminating radio and dusty submm sources. This will provide 10′′ resolution at 150 GHz (near the peak of the thermal SZ decrement) and a 2 degree instantaneous field of view. AtLAST is beginning to garner broad international support, with many US Astro2020 decadal and Canadian Long Range Plan 2020 submissions.
24
April 2020

Online: The Atacama Large Aperture Submm Telescope (AtLAST): Cosmological and Sunyaev-Zeldovich Effect Applications


Start: 12:15h
Speaker: Dr. Tony Mroczkowski (ESO)
Place: Online: Join Zoom Meeting https://zoom.us/j/346578843

The thermal and kinematic SZ effects provide a strong and independent complement to X-ray observations of the warm and hot ionised intracluster medium, particularly at high redshift where X-ray counts are limited. Being observable from the ground, new instruments for studying the SZ effects can be developed…
Start: 12:15h
Speaker: Dr. Tony Mroczkowski (ESO)
Place: Online: Join Zoom Meeting https://zoom.us/j/346578843

The thermal and kinematic SZ effects provide a strong and independent complement to X-ray observations of the warm and hot ionised intracluster medium, particularly at high redshift where X-ray counts are limited. Being observable from the ground, new instruments for studying the SZ effects can be developed more rapidly and can be upgraded more readily than their space-borne counterparts. I will discuss recent results from ALMA and MUSTANG2, as well as a newly-proposed research infrastructure (recently approved by the European Commission as a Design Study) for a 50-meter-class widefield submm/mm telescope called AtLAST. AtLAST will be capable of observing the multifaceted SZ effects and disentangling them from contaminating radio and dusty submm sources. This will provide 10′′ resolution at 150 GHz (near the peak of the thermal SZ decrement) and a 2 degree instantaneous field of view. AtLAST is beginning to garner broad international support, with many US Astro2020 decadal and Canadian Long Range Plan 2020 submissions.
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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