June 3, 2021 Dynamical Tests of Dark
Matter in the Milky Way
Speaker: Robyn
Sanderson, University
of Pennsylvania, Flatiron
Institute

The results of the Gaia
astrometric mission have ushered
in a new era of "precision
Galactic dynamics". Using this
new phase-space map of Galactic
stars with unprecedented volume
and accuracy, we are beginning
to obtain new insights into the
dark matter distribution in our
Galaxy as well as its formation
history. Thanks to significant
advances on the computational
front, meanwhile, we can now
compare these insights directly
with, and test our modeling
strategies on, simulations of
Milky-Way-mass galaxies where
the influence of baryons and the
cosmological context on the dark
matter structure are
realistically taken into
account. I will demonstrate how
this convergence of new data and
better models improves our
understanding of the Milky Way's
dark matter distribution,
leading to better constraints on
the nature of dark matter.
Watch the lecture.

June 10, 2021 Atmospheric Dynamics of
Hot-Jupiters
Speaker: James Cho, Flatiron
Institute

Close-in “hot
planets” present a new
opportunity for enriching our
understanding of atmospheric
dynamics of all planets. Not
only are they presently the most
well observed exoplanets,
subject to an unusual forcing
arrangement (i.e., steady
irradiation on the same side of
the planet throughout its orbit,
leading to “perpetual day and
night sides”), the dynamics on
these planets is also unlike
that on any of the solar system
planets. Moreover,
characterizing the flow pattern
and temperature distribution on
the extrasolar planets is
critical for reliable
interpretation of data currently
being collected, as well as of
data from large missions soon to
come online (e.g., JWST and
Ariel). In this talk, the flow
structures (e.g., storms and
jets) and the variability they
induce on a large class of
exoplanets, known as
“hot-Jupiters”, will be
discussed.
Watch the lecture.

June 17, 2021 Modeling the Within Host
Dynamics of SARS-CoV-2
Infection
Speaker: Alan S Perelson, Los
Alamos National Laboratory

SARS-CoV-2
has infected more than 170
million people and caused more
than 3.5 million deaths.
Mathematical modeling of the
infection dynamics within
individual hosts can provide
quantitative information about
disease pathogenesis and
host-viral interactions.
Here I will discuss recent
modeling work involving simple
target cell-limited models and
then more complex models with
innate immune responses, models
involving both upper and lower
respiratory tract infection, and
models of the effects of
antiviral agents given either
prophylactically or as
treatment. If time permits, I
will also discuss a mechanistic
model that aims to relate the
amount of virus in the upper
respiratory tract to the
probability of transmitting the
virus to another person during a
contact, and how this then
relates to issues of importance
in epidemiology.
Watch the lecture.

June 24, 2021 Searching for Massive Black
Holes in Dwarf Galaxies
Speaker: Vivienne Baldassare,Washington State University

The present-day population of
supermassive black holes in
low-mass galaxies offers a
window into massive black hole
formation in the early universe.
While we cannot yet observe the
formation of "black hole seeds"
at high redshift, the fraction
of small galaxies that host a
massive black hole -- and the
properties of those black holes
-- are thought to depend on the
mechanism by which they form.
However, black holes in the
smallest galaxies can be
difficult to find, requiring
creative new approaches. I will
present recent work showing that
long-term optical photometric
variability in low-mass galaxies
can identify active galactic
nuclei that are missed by other
selection techniques. I will
also discuss implications for
black hole formation and future
opportunities for progress with
upcoming surveys and facilities.
Watch the lecture.

July 1, 2021 Measuring the Radii of
Neutron Stars
Speaker: Coleman Miller,
University of Maryland

The last few
years have seen remarkable
progress in astronomical
measurements of neutron stars
that have bearing on the
properties of matter beyond
nuclear saturation
density. These
measurements include the
gravitational-wave constraint on
tidal deformability from the
double neutron star coalescence
GW170817, and measurements of
the radii of two neutron stars
of significantly different
masses (PSR J0030+0451 at ~1.4
solar masses, using data from
the NICER X-ray telescope, and
PSR J0740+6620 at ~2.1 solar
masses, using a combination of
NICER, XMM-Newton, and radio
data). I will discuss
these results and their
implications, with a particular
focus on the methods used to
obtain radii from X-ray
measurements, including an
evaluation of possible
systematic errors.
Watch the lecture.

July 8, 2021 Topological Quantum
Computation with
Majorana Zero Modes
Speaker: Roman Lutchyn,
Microsoft Station Q

Research in
quantum computing has offered
many new physical insights and a
potential to exponentially
increase the computational power
that can be harnessed to solve
important problems in science
and technology. The largest
fundamental barrier to building
a scalable quantum computer is
errors caused by decoherence.
Topological quantum computing
overcomes this barrier by
exploiting topological materials
which, by their nature, limit
errors. In this colloquium I
will discuss how to engineer
topological superconductors at
the interface of a conventional
superconductor and a
semiconductor with spin-orbit
interaction. I will discuss
recent experiments aiming to
detect Majorana zero-energy
modes at the ends of the
proximitized nanowires. Finally,
I will present designs for
scalable quantum computers
composed of qubits involving
superconducting islands in a
Coulomb blockade regime hosting
aggregates of four or more
Majorana zero modes.

July 15, 2021 The Universe from a
Single Particle
Speaker: Michael
Freedman, Microsoft
Station Q

This
talk derives from a
mathematical look at the
foundations of quantum
mechanics and attempts a
“creation story”. It is
based on joint work with
Modj Shokrian Zini,
arXiv:2011.05917. The
purest question “Why is
there something instead of
nothing?” seems out of
reach; we, instead,
attempt an answer to: “Why
does there appear to be a
multitude of things?” In
more technical language we
propose that spontaneous
symmetry breaking (SSB),
not on the usual level of
states but rather on the
level of (probability
distributions on
Hamiltonian) operators,
can “break” single
particle quantum mechanics
into interacting physics.
I will speculate at then
end on how this story may
eventually dovetail with
the more famous creation
stories: string theory and
ADS/CFT.

July 22, 2021 Supernovae Ignited by
Nuclear Fission: The Aspen
Primer
Speaker: Charles
Horowitz, Indiana
University

Type 1A
supernovae (SN Ia) are giant
stellar explosions that are
important distance indicators in
cosmology. Presently there
is tension between Hubble constant
values determined from SN and
other means. SN Ia are
thought to involve white dwarf
stars, but it is unclear how they
explode. We propose a new
mechanism involving a natural
nuclear fission explosion.
White dwarfs cool and eventually
crystalize. Our
molecular dynamics simulations
find that the first solids to
form, as the star cools, are
greatly enriched in actinides such
as uranium. This is because
actinides have the highest nuclear
charge. These solids may
support a fission chain reaction
that, in turn, could ignite carbon
fusion and explode the star.
This physics parallels that in
terrestrial nuclear weapons.

July 29, 2021 The Measurement Induced Phase
Transition in Open Quantum
Many-Body Systems
Speaker: Jedediah Pixley,
Rutgers University

The ability to control and measure
properties of quantum many-body
systems has reached an unprecedented
level of experimental accuracy. The
dynamical states that emerge in these
systems can be theoretically
characterized by their entanglement
structure. Generically, the unitary
time evolution of a quantum many-body
system couples its microscopic
constituents leading to a highly
entangled quantum state. On the other
hand, performing a global measurement
to learn something about the physical
content of the system will collapse
the wavefunction, destroying any
entanglement. However, if a quantum
system undergoing unitary time
evolution is measured locally at a
small but non-zero rate, it was
recently discovered that the highly
entangled state survives. Only after a
critical measurement rate will the
wavefunction essentially collapse
leading to a measurement induced phase
transition in the structure of the
entanglement. This talk will discuss
the recent progress in our
understanding of this measurement
induced phase transition in a wide
array of open quantum many body
systems. Focusing on a chain of
qubits we demonstrate that this
transition belongs to a novel
universality class that is described
by a non-unitary conformal field
theory with multifractal correlations
in space-time.

August 5, 2021 The Naturally Unnatural
Standard Model of Particle
Physics
Speaker: Nausheen Shah,
Wayne State University

The Standard
Model (SM) of Particle Physics
provides an excellent description of
nature. However, it is very much an
empirical model: Why are there 3
generations of matter with such
large mass hierarchies? What is the
origin of their mixings? What is
dark matter (DM)? What dynamics
govern the Higgs mechanism? If
Ultraviolet symmetry breaking
governs the structure we observe at
the weak scale, apparent
fine-tunings may be a hint of the
global structure dictating beyond
the SM physics. In this talk I will
discuss some fine-tunings that may
be responsible for the structure we
observe in Higgs couplings, fermion
masses and mixings, and possible
connections of the Higgs sector with
DM

August 12, 2021 Searching for New Particles in
the Sky
Speaker: Maria Baryakhtar, New
York University

Theories that seek to explain
the outstanding puzzles of the
Standard Model of particle
physics often predict new,
light, feebly-interacting
particles whose discovery
requires novel search
strategies. Perhaps the most
motivated of these particles
is the QCD axion, which can
elegantly solve the
outstanding strong-CP problem
of the Standard Model; cousins
of the QCD axion can also
appear, and are natural dark
matter candidates.In light of these
particles' small masses and
weak interactions, we turn to
the sky for clues of their
existence. We will see how
extreme astrophysical
environments --- from our Sun
to neutron stars to black
holes --- produce large
numbers of axions which lead
to indirect signatures, or can
be directly measured in the
lab. I will discuss how
rotating black holes source
exponentially large numbers of
gravitationally-bound axions,
creating nature's laboratories
for ultralight particles.
These systems emit
gravitational waves, allowing
observatories such as LIGO to
search for new particles. If
the axions interact with one
another, black holes instead
turn into axionic beacons,
populating the universe with
axion waves.

August 19, 2021 Extracting Dynamics in
Quantum Field Theory from
Conformal Field Theory
Data
Speaker: Andrew Liam
Fitzpatrick, Boston
University

A compelling view of Quantum
Field Theories (QFTs) is that
they are points along the RG
flow between fixed points
described by Conformal Field
Theories (CFTs), which in turn
are fully characterized by a
discrete set of "CFT data".In this talk, we describe
how this picture can be turned
into a useful calculational tool
for studying QFT at strong
coupling in infinite volume in
the continuum limit, by applying
a variational method motivated
by the conformal structure of
the ultraviolet CFT fixed point
of the theory.We demonstrate how
dynamical quantities can be
obtained, including energy
eigenvalue statistics,
Lorentzian correlation
functions, and the evolution of
excited states.

August 26, 2021 Machine Learning Quantum
Emergence
Speaker: Eun-Ah Kim, Cornell
University

Decades of efforts in
improving computing power and
experimental instrumentation
were driven by our desire to
better understand the complex
problem of quantum emergence.
The resulting "data revolution"
presents new challenges. I will
discuss how these challenges can
be embraced and turned into
opportunities through machine
learning. The scientific
questions in the field of
electronic quantum matter
require fundamentally new
approaches to data science for
two reasons: (1) quantum
mechanics restricts our access
to information, (2) inference
from data should be subject to
fundamental laws of physics.
Hence machine learning quantum
emergence requires collective
wisdom of data science and
condensed matter physics. I will
review rapidly developing
efforts by the community in
using machine learning to solve
problems and gain new insight. I
will then present my group’s
results on the
machine-learning-based analysis
of complex experimental data on
quantum matter.

September 2, 2021 NoTORIous Neutrinos
Speaker: Mu-Chun Chen,
University of California
Irvine

The discovery of non-zero
neutrino masses has provided
arguably the
most compelling evidence
for Physics beyond the Standard
Model. Their observed
small masses hint at
Physics at a very high energy
scale, and thus offers a
unique window into the
theory that underlies the
Standard Model of Particle
Physics. In this talk, I
will describe how the pattern of
neutrino masses may be closely
connected to the intricate
mathematics of modular
symmetries.

September 9, 2021 Searching for New Physics in
the Universe's Oldest Light
Speaker: Colin Hill,
Columbia University and Flatiron
Institute

I will
discuss recent and ongoing work
focused on attempts to restore
concordance amongst cosmological
data sets, motivated by
discrepancies amongst some
probes of the cosmic expansion
rate (H0) and the matter
clustering amplitude (S8).
Particular attention will be
paid to models invoking new
physics at or prior to
recombination, including
small-scale baryon-clumping
models (e.g., due to primordial
magnetic fields) and
quasi-accelerating early dark
energy models. In
particular, I will discuss
constraints on these scenarios
derived using the latest data
from the Atacama Cosmology
Telescope (ACT). I will
conclude with a look ahead to
forthcoming CMB measurements
from ACT, which will provide a
powerful test of these models in
the low-noise, high-resolution
regime.

September 16, 2021 Gravitational-wave
Detection, Macroscopic
Quantum Mechanics and Quantum
Gravity in the Lab
Speaker: Yanbei Chen, Caltech

Experimental
progress in quantum optomechanics
has allowed preparing, manipulating,
and probing the mechanical motions
of macroscopic objects in the
quantum regime. For example,
laser interferometer
gravitational-wave detectors are now
sensitive to displacements of
kg-scale test masses near the
free-mass Standard Quantum Limit,
which arises from applying the
Heisenberg Uncertainty Principle to
kg-scale test masses. Upcoming
and future upgrades of these
interferometers will benefit from
techniques that substantially
surpass the Standard Quantum Limit.
Quantum optomechanics also
provides new opportunities for
testing quantum mechanics, quantum
measurement theory, and possibly
studying the quantum nature of
gravity. If these tests confirm
conventional predictions, we will
demonstrate the validity of quantum
mechanics in unprecedented regimes.
Deviations from conventional
predictions will lead to new
physics.