Cosmology Seminar - Wednesday

• Date: 2/12/25
• Speaker: Prajwal Mohan Murthy
• Institution: Massachusetts Institute of Technology
• Faculty Host: Ricardo Alarcon 

Title: A New Search for the Electric Dipole Moment of the Neutron and “what will it take to discover a CPV EDM”?

Abstract: CP violation and consequently T violation endows the neutron with a non-zero electric dipole moment. Thus far, the known sources of CP violation in the Standard Model have been insufficient to explain the observed baryon asymmetry of the universe. Measuring a statistically significant nEDM is one way to gain a handle on the sources of CP violation in the SM and beyond. Therefore, a search for a permanent nEDM has been an ongoing effort for well over half a century.

The Paul Scherrer Institute Neutron Electric Dipole Moment (PSI nEDM) experiment is a room temperature experiment using the Ramsey technique of separated oscillating fields to search for a permanent electric dipole moment in neutrons. The PSI nEDM experiment uses ultracold neutrons (UCNs) and a cohabiting 199Hg magnetometer. The key upgrades of the PSI nEDM over previous generations of the experiments come in the form of a simultaneous spin analyzer and an array of 133Cs magnetometers. These upgrades provided PSI nEDM with an unprecedented control over systematics, thereby improving the systematics budget by a factor of 6. The PSI UCN source also is the most intense source of UCNs in the world, and this gave the experiment the best statistical sensitivity. The PSI nEDM experiment collected data from 2015 to 2017 and represents the most precise measurement of the EDM of the neutron. We will describe the background of nEDM in light of a plethora of other EDM searches and the result along with systematics.

Nuclear magnetic quadrupole moment (MQM), is also CP, P, and T violating. But the nuclear MQM is dramatically enhanced if the nuclei are structurally quadrupole deformed. If the nuclei are octupole deformed, in addition to quadrupole deformation, their CPV nuclear Schiff moment (NSM) can also be enhanced by 2-3 orders of magnitude. We will address questions like "which nuclei are the most enhanced systems in which to measure an EDM in?" and "when we measure an EDM, how can we tell apart the various sources contributing to it?".  We will also discuss modern approaches being investigated to search for CP violating moments in deformed nuclei and atoms, where the moments are vastly enhanced, along with quantum techniques. We will explore the various steps required to chart a path to measure a CPV EDM, and then interpret it, by bringing together techniques from Atomic and Low Energy Nuclear Physics. This path invariably goes through nuclear structure land!
 

• Date: 2/19/25
• Speaker: Yongda Zhu
• Institution: University of Arizona
• Faculty Host: Chris Cain 

Title:  Building a self-consistent picture between galaxies and gas on multiple scales

Abstract: Galaxies mark the peaks of the cosmic density field, while the vast, “invisible” reservoirs of intergalactic and circumgalactic medium (IGM/CGM) hold nearly 95% of the universe’s baryonic matter. Understanding the connection and evolution of these components is one of the key goals outlined in the Astro2020 Decadal Survey.
In this talk, I will present my work on studying the interplay between galaxies and their surrounding gas using observations from Keck, VLT, ALMA, and JWST. On the largest scales, I will discuss when and how reionization progressed from the Lya/Lyb forest data. On galactic scales, I will highlight our efforts to study multi-phase feedback using NIRCam and NIRSpec on JWST. Finally, on the smallest scales, I will share some new results on how accretion-driven winds link to galaxy-wide feedback processes in high-z quasars.  

• Date: 2/26/25
• Speaker: Timothy Heckman
• Institution: John Hopkins University
• Faculty Host: Sanchayeeta Borthakur 

Title: What quenches star formation in massive galaxies?

Abstract: The existence of a population of massive quiescent galaxies with little to no star-formation poses a challenge to our understanding of galaxy evolution. The most popular possibility is that feedback from supermassive black holes lifts or heats the gas that would otherwise be used to form stars. In this talk I will evaluate this idea by comparing the cumulative growth in the cosmic inventory of the total stellar mass in quiescent galaxies to the corresponding growth in the amount of kinetic energy carried by radio jets driven by supermassive black holes. These two inventories are remarkably well-synchronized, with about 50% of the total amounts being created in the epoch from z ≈ 1 to 2. I will also show that these agree extremely well with the corresponding growth in the cumulative number of major mergers that result in massive (> 1011 M_sun) galaxies. I will therefore argue that major mergers trigger the radio jets which heat/expel gas and quench star-formation. I will also evaluate the total amount of kinetic energy delivered by jets and compare it to this to the baryonic binding energy of the galaxies. This shows that the jet kinetic energy is more than sufficient to quench star-formation, and the quenching process should be more effective in more massive galaxies.

Date: 3/19/25

Speaker:  Curits Peterson

Institution: Michigan State University 

Faculty Host: Rich Lebed 

Title: Gradient flow renormalization: from beyond Standard Model physics to the precision frontier

Abstract: Gradient flow is a continuous smearing operation that can be interpreted as a real-space renormalization group transformation on coarse-grained expectation values. As such, gradient flow can be used to predict the non-perturbative renormalization group beta-function of a gauge-fermion system using techniques from lattice quantum field theory. In this seminar, I will show how gradient flow beta-functions can be used to determine both infrared fixed points in systems of interest to beyond Standard Model physics and the strong coupling constant of quantum chromodynamics.

Date: 3/26/25

Speaker: Anson D'Aloisio

Institution: UC Riverside 

Faculty Host: Chris Cain 

Title:  Cosmological Reionization: New Insights, New Puzzles

Abstract: When the first galaxies formed, their starlight reionized and heated the intergalactic hydrogen that had existed since recombination. In the past few years, there has been significant progress toward understanding the reionization process. I will highlight this progress, including the possibility that we have already observed evidence of reionization's tail end in the spectra of high-redshift quasars. I will also discuss (1) the role that small-scale structure in the cosmic web played in shaping reionization, (2) what we might learn about early galaxy formation and cosmology from reionization observables, and (3) a novel observational approach that may someday be used to map the reionizing intergalactic medium directly. Lastly, the improving constraints on reionization have turned up some new puzzles; I will discuss these too.

Date: 4/16/25

Speaker: Eric Perlmutter

Institution: 

Faculty Host: Cindy

Title:

Abstract: 

• Date: 9/11/24
• Speaker: Allic Sivaramakrishnan
• Institution: Caltech
• Faculty Host: Lars Aalsma

Title: Proper Time Correlators in Field Theory and Gravity

Abstract: Proper time is a simple classical observable, but its correlations are less well understood. We define correlation functions of proper time for massive worldlines coupled to quantum field theory and quantum gravity, and we show how to compute perturbative corrections using Feynman diagrams. 

When the worldline endpoints are held fixed, proper time correlators are derivatives of the on-shell action with respect to mass, or more generally, derivatives of the logarithm of local correlators. This clarifies how CFT correlators encode AdS worldline data. When the worldline endpoints are dynamical and determined relationally in a gravitational system, the proper time delay operator is a smeared graviton operator to leading order. The proper time two-point function computes the leading-order signature of quantum gravity in a toy model of a LIGO-type interferometer. This prediction agrees qualitatively with the experimental observable computed in a more realistic model.

• Date: 9/18/24
• Speaker: Evgenii Ievlev 
• Institution: University of Minnesota 
• Faculty Host: Paul

Title: Black hole radiation through the mirror of classical electrodynamics

Abstract:  Moving mirrors, or Dynamical Casimir effect, is a phenomenon of particle creation induced by a reflective boundary that moves with an acceleration. This phenomenon when considered in 1+1 dimensions can be described by a conformal field theory with a boundary, which allows one to obtain a great variety of exact results concerning particle production.

We will begin with a general introduction into the mechanism of the dynamical Casimir effect in 1+1, and then discuss its connection to black hole radiation. We will also cover the electron-mirror duality that was recently brought into quantitative form, and discuss some unexpected developments related to the neutron beta decay.

Date: 9/25/24

Speaker: Bharat Ratra

Institution: Kansas State University 

Faculty Host: Tanmay Vachaspati

Title: Cosmological Seed Magnetic Field from Inflation

Abstract: A cosmological magnetic field of nG strength on Mpc length scales could be the seed magnetic field needed to explain observed few microG large-scale galactic magnetic fields. I first briefly review the observational and theoretical motivations for such a seed field, two galactic magnetic field amplification models, and some non-inflationary seed field generation scenarios. I then discuss an inflation magnetic field generation model. I conclude by mentioning possible extensions of this model as well as potentially observable consequences.

Date: 10/9/24

Speaker: Haochen Wang

Institution: MIT

Faculty Host: Simon Foreman

Title: New Cross-Correlation Techniques with CHIME

Abstract: The Canadian Hydrogen Intensity Mapping Experiment (CHIME) is a radio interferometer that aims to map out the large-scale structure of the universe through two types of observations: 1) detecting the accumulated hydrogen 21 cm line emission from galaxies, and 2) tracing the baryon distribution along the line of sight of energetic radio transient events called fast radio bursts (FRBs). In this talk, I will introduce new cross-correlation techniques to mitigate challenges for both types of observations. The major roadblock to detecting the 21 cm signal is foreground emissions mostly from the Milky Way. I will present a new family of algorithm, called HyFoReS, that can separate the 21 cm signal from foregrounds by cross correlating linearly filtered data. On the other hand, FRBs are being detected with high signal-to-noise ratio, but we lack mature data processing tools to constrain cosmology from them. I will show the prospect of cross-correlating the dispersion measure of FRB signals with galaxy surveys to probe the electron distribution in the inter-galactic medium, with important cosmological implications such as constraining galaxy feedback and breaking degeneracies for future CMB surveys.

Date: 10/16/24

Speaker: Joshua Foster

Institution: MIT

Faculty Host: Tanmay 

Title: 

Abstract: 

Date: 10/30/2024

Speaker: Benoit Assi

Institution: Fermilab

Faculty Host: Matt Baumgart

Title:  Geometry of Effective Field Theories

Abstract: The geometry of field space governs on-shell scattering amplitudes in effective field theories. Extending previous geometric descriptions for scalars and gauge fields, I will discuss how we developed a framework that incorporates fermions into the geometric formulation of effective field theories. Utilizing this field-space geometry, we reorganize and simplify quantum loop corrections, calculating the one-loop contributions to the renormalization group equations for bosonic operators in the SMEFT up to mass dimension eight. I will further discuss structures in EFT not captured by the geometric framework, namely energy-enhanced effects arising from higher-dimensional operators. In particular, I will present our study on Higgs boson production via VBF at the LHC, and capturing the leading energy-enhanced contributions within the SMEFT up to mass dimension eight. Employing energy-scaling arguments, we predict the magnitude of each higher-dimensional operator's contribution and incorporate dimension-eight operators not previously considered. Our findings suggest that dimension-eight operators can have significant effects in regimes where the SMEFT remains valid for lower cutoff scales than expected.

Date: 11/06/2024

Speaker: Temple He

Institution: Caltech

Faculty Host: Lars Aalsma

Title:  From 't Hooft to BMS: Connecting Shockwaves and Memories

Abstract: We study the infrared on-shell action of Einstein gravity in asymptotically flat spacetimes, obtaining an effective, gauge-invariant boundary action for memory and shockwave spacetimes. We show that the phase space is in both cases parameterized by the leading soft variables in asymptotically flat spacetimes, thereby obtaining an equivalence between shockwave and soft commutators. We then demonstrate that our on-shell action is equal to three quantities studied separately in the literature: (i) the soft supertranslation charge; (ii) the shockwave effective action; and (iii) the soft effective action. 

Date: 11/13/2024

Speaker: Yuri Shirman

Institution: UC Irvine

Faculty Host: Matt Baumgart

Title:  Chirality changing RG flows dynamics and models

Abstract: In this talk I will discuss chiral properties of strongly interacting supersymmetric gauge theories. A long standing lore states that the mass for chiral fermions can only be generated if chiral symmetry is broken, either explicitly or spontaneously. There are, however, examples of supersymmetric chiral models where non-perturbative dynamics can change the chiral structure of the theory. We will carefully analyze the strong coupling dynamics responsible leading to chirality change and clarify the condition under which chirality flows are consistent with existence of the stable vacua. We will point out consequences of our result for string model building.

• 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: The interplay between gravitational wave astrophysics and cosmological observations

Abstract: From the population of coalescing compact objects observable as gravitational wave transients, it is clear that cosmological effects will have a great impact as both a novel way to explore cosmological measurements and as a strong piece of inference to anchor much of our astrophysical understanding.

I will present an overview of cosmological measurements only possible through gravitational wave observations, as well as methods of inferring the astrophysics governing the population of black holes and neutron stars we’re observing where its direct dependance on cosmological variation and evolution provides the crucial foundation on which the inference is based.

Date: 5/1/2024

Speaker: Muldrow Etheredge

Institution: UMass Amherst/KITP

Faculty Host: Lars 

Title: Sharpening Swampland Conjectures

Abstract: The Swampland program aims to distinguish theories that can come from string theory from those that cannot. This program involves mathematical experiments, where conjectures are formulated, mathematically tested in string compactifications, and sometimes refined. The ultimate aim is to a) make predictions about experiments in our universe and b) better understand what string theory and quantum gravity fundamentally are. In recent years, many of these conjectures have become stronger and more constraining. In this talk, I will give an introduction to the Swampland program and discuss some recent progress in strengthening Swampland conjectures.