Cosmology Seminar - Wednesday

• Date: 1/3/24
• Speaker: Glennys Farrar
• Institution: NYU
• Faculty Host: Lars Aalsma

Title: Breakthrough on the source(s) of UHECRs

Abstract: The origin of Ultrahigh Energy Cosmic Rays has been one of the most elusive problems in astrophysics for more than half a century since their existence started to be established.  Thanks to the serendipitous arrival direction of the Amaterasu particle with nominal energy of 244 EeV (2.4 $10^{20}$ eV), recently reported by the Telescope Array, and recent advances in our understanding of the Galactic magnetic field, we can localize its source to a volume which is practically devoid of any sufficiently powerful steady-source candidates.  This is a smoking gun that at least this UHECR was produced by a transient event in an otherwise undistinguished galaxy, such as a Tidal Disruption Event or compact binary merger.  I will describe this analysis as well as some complementary recent population-level constraints pointing in a similar direction, and discuss some of the most pressing open issues for the field.

• Date: 2/21/04
• Speaker: Joel Meyers
• Institution: SMU
• Faculty Host: Simon Foreman

Title: New Opportunities and New Challenges with Upcoming CMB Surveys

Abstract: Future surveys will map the cosmic microwave background (CMB) with unprecedented precision.  The high fidelity of the data will present new opportunities to extract deep insights about the history, contents, and evolution of our universe.  However, new tools and techniques will be required to maximize the potential of the forthcoming data.  I will describe the techniques necessary to address the emerging challenges and to harness the exciting opportunities provided by future CMB observations.

Date: 2/28/04

Speaker: William Munizzi

Institution: ASU

Faculty Host: Raphaela Wutte

Title: Holographic Dual of Magic

Abstract: Not all quantum computations are created equal. Certain systems, e.g. stabilizer states, can be efficiently simulated on a classical computer, while others require advanced fault-tolerant quantum computers to accurately describe. One measure of simulation difficulty, known as quantum magic, quantifies the non-stabilizerness in a particular system. While magic is intimately related to entanglement, the two properties do not give equivalent predictions of quantum complexity. Nonetheless, both features play a complementary role when describing emergent gravity in AdS/CFT. For holographic conformal field theories, the classical gravity dual of entanglement is a set of bulk geodesics, known as Ryu-Takayanagi surfaces. In this talk I will present an analogous holographic dual for magic, and discuss the relationship between magic and entanglement.

Date: 3/13/24

Speaker: Michael Wagman

Institution: ASU

Faculty Host: Matt 

Title: Do dark nuclei bind?

Abstract: Since almost all of the energy density of visible matter is carried by quarks and gluons bound into nucleons and nuclei, it is natural to wonder if much of dark matter can be described by a strongly interacting gauge theory. Whether analogs of big bang nucleosynthesis occur in the dark sector and the structure of dark matter today depend on how the analogs of nuclear forces behave for gauge theories beyond QCD. I will discuss lattice QCD and effective field theory calculations that explore how nuclear forces depend on the masses of strongly interacting fermions.

Date: 3/20/24

Speaker: Axel Brandenberg

Institution: Nordita, Stockholm

Faculty Host: Tanmay 

Title: Why are astrophysical plasmas always magnetized?

Abstract: Long ago, magnetic fields in astrophysics used to be something
for specialists. This has drastically changed over the past few
decades. Nowadays, many scientists invoke magnetic fields in simulations
of astrophysical flows. In fact, the concept of purely hydrodynamic
turbulence without magnetic fields seems to be an idealization that
hardly exists anywhere. We now understand that this is because of the
universality of dynamo action in many types of flows. Dynamos convert
kinetic energy into magnetic; they are self-excited and work without
wires, but without short-circuiting themselves in spite of their high
conductivity everywhere.

In my talk, I will start with a historical perspective, going back to
the days when the existence and origin of magnetic fields was still
very obscure. We knew about the Earth's magnetic field since the 1600s,
and astronomical observations have revealed magnetic fields in sunspots
and eventually in other stars and galaxies during the last century. To
understand their origin, people had to struggle with Cowling's anti-dynamo
theorem that magnetic fields cannot be generated from kinetic energy
in a simple axisymmetric geometry. Gradually, it became clear that in
three-dimensional settings, self-excited dynamos do actually work.

Meanwhile, with the emergence of three-dimensional simulations, where
the plasma motions tend to be turbulent, dynamo action appears to
be a natural by-product. Dynamos have also been realized in the lab
in various configurations. But some basic questions in astrophysical
applications are still troubling us: why exactly is the Sun's magnetic
field exhibiting equatorward migration and why do the most realistic
simulations not yet reproduce the large-scale magnetic fields observed
in spiral galaxies by the present time. I will finish with applications
to the early Universe, where decaying magnetic turbulence governs the
entire radiation-dominated era and many of the relationships can be
understood from dimensional arguments.

Date: 3/27/24

Speaker: Zack Li

Institution: UC Berkeley 

Faculty Host: Simon 

Title: Cosmology at redshifts 50 and 1100

Abstract: 

At high redshift, we can cleanly separate physics from astrophysics. Things were simpler back then. I'll discuss two upcoming experiments that chase those good old days before star formation changed everything. 

LuSEE-Night is a pathfinder 21 cm experiment with four monopoles headed to the lunar farside in 2026, seeking the redshifted 21 cm line from the Dark Ages. In a similar timeframe, the Simons Observatory will make incredibly precise maps of the Cosmic Microwave Background from the Atacama Desert. I'll discuss the status of these experiments and the challenges they face in uncovering new physics.

Date: 4/10/2024

Speaker: Biplab Dey

Institution: Cern

Faculty Host: Rich 

Title:  Journeys beyond the Standard Model in the flavor and dark sectors at the LHC

Abstract: I will discuss a proposal to probe New Physics beyond the Standard Model via a two-prong approach at the LHC. New heavy particles, beyond the reach of direct searches at ATLAS/CMS, can leave behind their imprints in rare, loop-induced decays of the beauty quark to strange or down quark. I will describe the ongoing efforts and challenges in the flavor sector at LHCb. A particular thrust is multi-dimensional amplitude analyses to cleanly separate New Physics effects from QCD-induced “pollution” in such processes. New Physics can also exist in a hidden/dark sector at lower energies, if the new particles have very long-lifetimes and thereby escape detection at the LHC, since the detectors and triggers are tuned for particle decays close to the interaction point. Such long-lived particles arise ubiquitously in almost every extension of the Standard Model. To ensure that the upcoming High-Luminosity LHC runs can probe long-lived particles that travel several meters before decaying, a new sub-detector, CODEX-b, is proposed to be installed in a shielded region inside the LHCb cavern. I will describe the status and future plans of the CODEX-b project, aligned with the LHCb future upgrades effort.

Date: 4/17/2024

Speaker: Mainak Mukhopadhyay

Institution: The Pennsylvania State University

Faculty Host: Tanmay 

Title:  Multi-messenger signatures from extreme astrophysical phenomena

Abstract:  In the current era of multi-messenger astronomy, gravitational wave (GW), neutrino, photon, and cosmic ray observations are combined to extract information about astrophysical sources and phenomena in the Universe. In this talk, I will discuss some aspects of multi-messenger observations associated with tidal disruption events (TDEs) and binary neutron star (BNS) mergers. In particular, recent radio observations and coincident neutrino detections suggest that some tidal disruption events (TDEs) exhibit late-time activities relative to the optical emission peak. I will discuss the multi-messenger implications of delayed choked jets in TDEs, which could be a plausible explanation for the late-time activity (https://arxiv.org/abs/2309.02275). Additionally, I will discuss the possibility and prospects of performing stacked triggered searches for high-energy neutrinos from BNS mergers using the next generation GW detectors at IceCube-Gen2 (https://arxiv.org/abs/2310.16875).

Date: 4/24/2024

Speaker: Carl Hester

Institution: UNLV

Faculty Host: Simon 

Title: 

Abstract: 

Date: 5/1/2024

Speaker: Muldrow Etheredge

Institution: UMass Amherst/KITP

Faculty Host: Lars 

Title: 

Abstract: