# Found 7 talks width keyword *gravitation*

## Abstract

In the local universe most of the stellar mass is in passive galaxies, where star formation is

absent or at very low levels. Understanding what are the mechanisms that have been

responsible for quenching star formation in galaxies, and transforming them into passive,

quiescent systems, is one of the main observational and theoretical challenges of extragalactic

astrophysics. I will give a brief overview of the several possible quenching causes and physical

processes that have been proposed so far, ranging from feedback from black hole accretion and

starburst activity, to effects associated with the large scale environment in which galaxies live.

Although most of these mechanisms and causes play a role in different classes of galaxies and

at different epochs, multi-band observations are providing growing evidences that just a few of

them play the key, dominant role.

I will conclude by providing prospects for further investigating these aspects and tackling open

questions with the next generation of observing facilities.

## Abstract

## Abstract

Bosonic ultra-light dark matter (ULDM) in the mass range m ~ $10^{-22} - 10^{-21} \rm eV$ has been invoked as a motivated candidate with new input for the small-scale `puzzles' of cold dark matter. Numerical simulations show that these models form cored density distributions at the center of galaxies ('solitons'). These works also found an empirical scaling relation between the mass of the large-scale host halo and the mass of the central soliton. We show that this relation predicts that the peak circular velocity of the outskirts of the galaxy should approximately repeat itself in the central region. Contrasting this prediction to the measured rotation curves of well-resolved near-by galaxies, we show that ULDM in the mass range m ~ $10^{-22} - 10^{-21} \rm eV$ is in tension with the data.

## Abstract

Things should be made simple, but not simpler.

What we want to show is that General Relativity, as it stands today, can be considered as a gravitational theory of low velocity spinless matter, and therefore a restricted theory of gravitation.

Gravity is understood as a geometrization of spacetime. But spacetime is also the manifold of the boundary values of the spinless point particle in a variational approach. Since all known elementary matter, baryons, leptons and gauge bosons are spinning objects, it means that the manifold, which we call the kinematical space, where we play the game of the variational formalism of a classical elementary particle must be greater than spacetime.

Mathematics shows that this manifold for any arbitrary mechanical system is always a Finsler metric space, such that the variational formalism can be interpreted as a geodesic problem on this metric space.

This manifold is just the flat Minkowski space for the free spinless particle. Any interaction modifies its flat Finsler metric as gravitation does.

The same thing happens for the spinning objects, but now the Finsler metric space has more dimensions and its metric is modified by any interaction, so that to reduce gravity to the modification only of the metric of the spacetime submanifold is to make a simpler theory, the gravitational theory of spinless matter.

Even the usual assumption that the modification of the metric only produces a Riemannian metric of the spacetime is also a restriction because in general the coefficients for a Finsler metric, are also dependent on the velocities. Removal of the velocity dependence of metric coefficients is equivalent to consider the restriction to low velocity matter.

In the spirit of unification of all forces, gravity cannot produce, in principle, a different and simpler geometrization than any other interaction.

References: arXiv: 1203.4076

## Abstract

Contrary to popular belief, on very large distance scales visible matter stubbornly refuses to "fall" according to the laws of gravity of both Newton and Einstein. The paradox has led to the introduction of dark matter, purporting to explain the observed surplus of gravitational pull. The logical possibility remains that there is no dark matter, what you see is all there is, and that the paradox simply signals the break down of the Einstein-Newton theory of gravity. I will review alternative theories of gravity that do away with the need for dark matter. Surprisingly Solar system gravitational experiments, such as those associated with the LISA Pathfinder mission, might settle the score between the two approaches.## Abstract

A Friedman-like cosmological model, based on noncommutative geometry, is presented. Its Planck level is totally nonlocal with no space and no time. The dynamics on this level is strongly probabilistic which makes the initial singularity statistically insignificant. Space, time and the standard dynamics emerge when one goes from the non-commutative regime (on the Planck level) to the usual "commutative physics".

## Abstract

The standard model of cosmology -- the ``Lambda cold dark matter'' model -- is based on the idea that the dark matter is a collisionless elementary particle, probably a supersymmetric particle. This model (which mostly dates back to an early workshop in Santa Barbara in the 1980s) has been famously verified by observations of the cosmic microwave background radiation and the large-scale distribution of galaxies. However, the model has yet to be tested conclusively on the small scales appropriate to most astronomical objects, such as galaxies and clusters. I will review our current understanding of the distribution of dark matter on small scales which derives largely from large cosmological N-body simulations and I will discuss prospects for detecting dark matter, either through its gravitational effect on galaxies and clusters or, more directly, through gamma-ray annihilation radiation.« Newer Older »

## Upcoming talks

**TODAY:**(Almost) Thirty Years of the Sq-Polytropic Connection – An Overview on Some Basic Aspects of the Sq-based TherostatisticsProf. Ángel Ricardo PlastinoThursday May 26, 2022 - 10:30 GMT+1 (Aula)- Descripción y estado actual de GRANCAINDr. José Miguel Delgao HernándezFriday May 27, 2022 - 12:00 GMT+1 (Aula)