« fall 2017 - spring 2018 - summer 2018 »

This week | Next week | This semester | All future | Print view

This week | Next week | This semester | All future | Print view

Tuesday, January 23rd 2018

2:30 pm:

Nuclear matter has a complex phase structure, with a deconfined Quark-Gluon Plasma (QGP) expected to be present under conditions of extreme pressure and temperature. The hot QGP filled the universe about few microseconds after the Big Bang. This hot nuclear matter can be generated in the laboratory via the collision of heavy atomic nuclei at high energy. I will review recent theoretical progress in studying the transport properties the QGP at almost zero baryon density. The recent beam energy scan experiments at the Relativistic Heavy-Ion Collider (RHIC) offer a unique opportunity to study the nuclear phase diagram in a hot and baryon-rich environment. I will focus on the development of a comprehensive framework that is able to connect the fundamental theory of strong interactions with the RHIC experimental observations. This dynamical framework paves the way for quantitative characterization of the QGP and for locating the critical point in the nuclear phase diagram. These studies will advance our understanding of strongly interacting many-body systems and build interconnections with other areas of physics, including string theory, cosmology, and cold atomic gases.

Friday, January 26th 2018

10:10 am:

Friday, February 2nd 2018

10:10 am:

Tuesday, February 6th 2018

2:30 pm:

How are neutron stars formed and what is inside them? What is the

engine powering short gamma-ray bursts? What is the astrophysical site

of production of heavy elements? Multimessenger observations of

compact binary coalescence and core-collapse supernovae might provide

us with the key to answer these and other important open questions in

theoretical astrophysics. However, multimessenger astronomy also poses

new challenges to the theorists who need to develop models for the

joint interpretation of all data channels. In this talk, I will

present recent theoretical results. I will review the landmark

multimessenger observation of merging neutron stars, and I will

discuss its interpretation and implication in the light of results

from first-principles simulations. Finally, I will discuss future

challenges and prospective for this nascent field.

Friday, February 9th 2018

10:10 am:

Friday, February 16th 2018

10:10 am:

Tuesday, February 20th 2018

2:30 pm:

Microseconds after the Big Bang, the Universe cooled into an exotic phase of matter. There the fundamental building blocks of Quantum Chromodynamics (QCD), known as quarks and gluons, were not confined inside the core of atomic nuclei. Tiny specks of this early Universe matter, called the Quark-Gluon Plasma (QGP), are now being copiously produced in heavy ion collisions at both RHIC and the LHC. These experiments provide overwhelming evidence that the QGP flows like a nearly frictionless strongly coupled liquid over distance scales not much larger than the size of a proton. Thus, the QGP formed in particle colliders is the hottest, smallest, densest, most perfect liquid known to humanity. Yet, the theoretical underpinnings behind the liquid-like behavior of QCD matter remain elusive.

In this talk I will present first principles calculations performed within string theory and relativistic kinetic theory that have shed new light on the emergence of hydrodynamic behavior in QCD and challenged the very foundations of fluid dynamics. New techniques to determine the real time, far-from-equilibrium dynamics of QCD in the large baryon density regime will also be discussed to lead current experimental efforts to discover critical phenomena in the fundamental theory of strong interactions.

Friday, February 23rd 2018

10:10 am:

Friday, March 2nd 2018

10:10 am:

Tuesday, March 6th 2018

2:30 pm:

The first detection in August 2017 of a binary neutron star merger in gravitational and electromagnetic waves marked the beginning of the era of multi-messenger astronomy. Future detections of neutron star-neutron star (NSNS) and neutron star-black hole (NSBH) mergers will allow astrophysicists to understand these systems in unprecedented detail, and test key theories about these exotic events. Two questions are especially interesting from a nuclear physics standpoint. First, what is the structure of ultra-dense neutron stars? Second, what is mergers' role in seeding the Universe with heavy elements synthesized via rapid neutron capture (the r-process)?

I will discuss how observations of mergers can help us answer these questions.

I will focus particularly on the radioactive transients that accompany mergers (the so-called "kilonovae"), and explain how recent theoretical advances allow us to use kilonova observations to constrain open questions in nuclear astrophysics.

Friday, March 9th 2018

10:10 am:

Wednesday, March 21st 2018

2:30 pm:

The phases of matter at extreme temperatures and densities are essentially determined by strong nuclear interactions. But for most temperatures and densities, we lack the theoretical tools to efficiently study QCD, the quantum field theory describing the strong nuclear force. For instance, in much of the phase diagram of QCD, there are very few well-defined order parameters to label its phases. I will describe recent advances in understanding the symmetries and order parameters of QCD, with a focus on the implications for understanding the phase diagram of nuclear matter as a function of temperature and density.

Friday, March 23rd 2018

10:10 am:

Friday, March 30th 2018

10:10 am:

Friday, April 6th 2018

10:10 am:

Friday, April 13th 2018

10:10 am:

Friday, April 20th 2018

10:10 am:

Friday, May 4th 2018

10:10 am:

Friday, May 11th 2018

10:10 am:

Tuesday, September 11th 2018

11:15 am:

Tuesday, September 18th 2018

11:15 am:

Tuesday, September 25th 2018

11:15 am:

Primordial black holes form in the early universe when over-dense regions gravitationally collapse upon horizon reentry. While there are many proposed formation mechanisms, inflation is an attractive candidate due to curvature perturbations that are generated. Inflation models that exhibit an inflection point in their potentials are seen to give rise to enhancements in the power spectrum during horizon exit, which can produce PBHs, that are long-lived, at sufficient abundances- while also satisfying observational constraints. Lastly, if not all, a fraction of current dark matter content may be comprised of PBHs.

Tuesday, October 2nd 2018

11:15 am:

It is believed that cold dense quark matter is a "color-superconducting" state of matter. What does that mean? Is this sharply different from a standard "confirmed" nuclear superfluid? I'll give a basic overview of recent progress on these formal questions, with a warm up discussion of standard electromagnetic aupercondtivity the answers to the above questions have interesting physical consequences for the quantization of angular momentum of quasiparticle excitations in dense quark matter.

Tuesday, October 9th 2018

11:15 am:

Supernova explosions of massive stars provide an important

contribution to the chemical enrichment of the galaxy and neutrinos

and their interactions with nuclei play a crucial role in that

environment. I will give an overview of the role of neutrinos for

supernova explosions and present recent progress in nucleosynthesis

calculations for the neutrino process, that combine state-of-the art

nuclear models and astrophysical modelling.

Tuesday, October 16th 2018

11:15 am:

Cold dense quark matter is a superfluid, but not quite the

familiar one we learned about in textbooks. Instead, it is a

"topologically-enriched" superfluid. I'll explain how to derive a

local effective action for this gapless phase of matter, which

involves coupling the superfluid to a topological quantum field theory

(TQFT). Along the way we'll talk about continuum "BF" actions for

four-dimensional discrete gauge theories, as well certain peculiar

five-dimensional cousins of these TQFTs relevant for our superfluids.

This talk is a more technical follow-up to a talk from two weeks ago,

but will be aimed to be followable by people who didn't attend the

first talk.

Tuesday, October 23rd 2018

11:15 am:

Tuesday, November 6th 2018

11:15 am:

Tuesday, November 13th 2018

11:15 am:

Tuesday, November 20th 2018

11:15 am:

In this talk I will discuss the effects of hydrodynamic

fluctuations in non-relativistic and relativistic setups. Within the

framework of stochastic hydrodynamics I obtain a number of model

independent results, including the long-time tail of different

transport coefficients, and the leading non-analyticity of the

correlators of energy, momentum and particle density in

non-relativistic and relativistic setups. The presence of hydrodynamic

fluctuations induce lower bounds on the transport coefficients by

analyzing the low frequency limit of different correlation functions.

I determine the lower bounds of the bulk viscosity over entropy ratio

in a cold Fermi gas near unitarity. When extending this analysis to

the case of a U(1) conformal relativistic expanding fluid we observe

that the values of the shear viscosity and heat conductivity are

bounded from below. In both setups, non-relativistic and relativistic

one, the lower bounds on the transport coefficients are weakly

dependent on assumptions regarding the range of applicability of fluid

dynamics.

Tuesday, November 27th 2018

11:15 am:

Since the incident nuclei in heavy-ion collisions do not

carry strangeness, the global net strangeness of the detected hadrons

has to vanish. We show that there is an intimate relation between

strangeness neutrality and baryon-strangeness correlations. In the

context of heavy-ion collisions, the former is a consequence of quark

number conservation of the strong interactions while the latter are

sensitive probes of the character of QCD matter. We investigate the

sensitivity of baryon-strangeness correlations on the freeze-out

conditions of heavy-ion collisions by studying their dependence on

temperature, baryon- and strangeness chemical potential. The impact of

strangeness neutrality on the QCD equation of state at finite chemical

potentials will also be discussed. We model the low-energy sector of

QCD by an effective Polyakov loop enhanced quark-meson model with 2+1

dynamical quark flavors and use the functional renormalization group

to account for the non-perturbative quantum fluctuations of hadrons.

Tuesday, December 4th 2018

11:15 am:

During a supernova vast numbers of neutrinos are released.

The energy of this neutrino emission dwarfs that of the light from the

explosion, yet the neutrinos are much more difficult to detect. I will

provide an overview of supernova neutrino detection techniques, and

discuss some of the information that might be learned from such a

detection.

Tuesday, December 11th 2018

11:15 am:

Tuesday, December 18th 2018

11:15 am:

The weekly calendar is also available via subscription to the physics-announce mailing list, and by RSS feed.