Physics and Astronomy Calendar

All future


Monday, November 27th 2017
12:15 pm:
Speaker: Nader Mirabolfathi, Texas A&M University
Subject: From Single-Electron Resolution Phonon-Mediated Detectors To Directional Dark Matter Searches

Direct detection dark matter experiments are striving to develop technologies that allow for ultra low-threshold large modular mass detectors. After a brief overview of the current efforts in the field, I will discuss our new studies suggesting that at the quantum electronic excitation level, solid state detectors exhibit significant directional sensitivity to DM interactions. The solar neutrino-nucleus elastic coherent scattering will soon become the irreducible background for direct detection experiments. Directional sensitivity offers a solution to further gain in DM sensitivity beyond this so called "neutrino floor".

Faculty Host: Priscilla Cushman

Wednesday, November 29th 2017
Speaker: Marvin Marshak, University of Minnesota
Subject: Neutrino Experiments at the Soudan Underground Laboratory

I will discuss the 38-year history of proton decay and neutrino experiments
at the Soudan Underground Laboratory, with a focus on the early history
of how and why the lab started and how it developed an extensive program
of physics experiments.

7:00 pm:
Speaker: Philip Kim, Harvard University
Subject: Stacking atomic layers: quest for new materials and physics

Modern electronics has been heavily relied on the technology to confine electrons in the interface layers of semiconductors. In recent years, scientists discovered that various atomically thin materials including graphene, a single atomic carbon layer, can be isolated. In these atomically thin materials, quantum physics allows electrons to move only in an effective 2-dimensional (2D) space. By stacking these 2D quantum materials, one can also create atomic-scale heterostructures with a wide variety of electronic and optical properties. I will discuss the creation of new heterostructures based on atomically thin materials and emerging new physics with technological implications therein.


Thursday, November 30th 2017
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: David Odde, University of Minnesota
Subject: To be announced.
Speaker: Vihang Mehta and Tom Jones
3:35 pm:
Speaker: Philip Kim, Harvard University
Subject: Unusual quasiparticle correlation in graphene
Fall 2017 Van Vleck Lecturer

Interactions between particles in quantum many-body systems can lead to a collective behavior. In a condensed matter system consisting of weakly interacting particles, a propagating particle interacting with its surroundings can be viewed as a ‘dressed’ quasiparticle with renormalized mass and other dynamic properties. The lack of screening enables strong Coulomb interactions between charged particles, leading to new collective dynamics. In this talk, I will discuss three examples concerning strongly interacting quasiparticles in graphene. In the first example, it will be shown that the thermally populated electrons and holes to realize Dirac fluid, where a huge violation of Wiedemann-Franz law is observed. The second example is realizing magnetoexcitons to correlated the quasiparticles in quantized Landau levels to form magnetoexcitons, which can condense into Bose-Einstein condensation. Finally, we will also discuss another way of correlated quasi-particles in graphene using superconducting proximity effect. Here, we employ the crossed Andreev reflection across thin type II superconducting electrodes to correlated spatially separated quasiparticles. Under strong magnetic fields, the quantum Hall edge states can carry these quasiparticles.


Friday, December 1st 2017
10:10 am:
Nuclear Physics Seminar in Tate 301-20
Speaker: Rajan Gupta, LANL
Subject: Probing TeV physics with precision calculation of nucleon Structure using lattice QCD.

This talk will present a number of high precision results on matrix
elements of quark bilinear operators between nucleon states using
lattice QCD. From these, we extract a number of exciting quantities,
at the intersection of nuclear and particle physics. We show that the
accuracy with which axial charge gA- , a fundamental parameter encapsulating the weak interaction of nucleons, can be calculated. Results for the scalar and tensor charges, g_S and g_T, which combined with precision neutron decay distribution probe novel scalar and tensor interactions at the TeV scale. Vector form factors are probed in electron scattering, while axial vector form factors are used in the calculation of the cross-section of neutrinos on nuclear
targets. These energy dependent cross-sections are needed to determine the neutrino flux, an important systematic in neutrino oscillation experiments. Finally we will present results for flavor diagonal charges that provide the contribution of the quark spin to the nucleon spin, the quark EDM to the neutron EDM, and needed to determine the cross-section of dark matter with nuclear targets.

Speaker: Vitaly Vanchurin (UMN Duluth)
Subject: General Relativity from Non-Equilibrium Thermodynamics of Quantum Information

In this talk I will argue that general relativity may be viewed as a useful limit of quantum mechanics with many degrees of freedom, very much like thermodynamics is a useful limit of classical mechanics with many degrees of freedom. First, I will construct statistical ensembles of ket-vectors using spatially covariant dual field theories with a metric tensor playing the role of a conjugate thermodynamic variable to the so-called information tensor (which is related to both Fisher matrix and Fubini-Study metric). Secondly, I will analyze evolution of the ensembles of ket-vectors to argue that an approximate space-time covariance of the dual field theories can be achieved if certain quantum computational complexities are minimized. And finally, I will show that minimization of a non-equilibrium entropy production can lead to the Einstein-Hilbert dynamics of the metric tensor for a particularly simple and highly symmetric form of the Onsager tensor.

Speaker: Shea Brown, U of Iowa
Refreshments to be served in the MIfA Interaction Area (Tate 285-11) following the colloquium.
Faculty Host: Lawrence Rudnick
Speaker: Nora Berenstain, Department of Philosophy - University of Tennessee-Knoxville
Subject: Active Ignorance and the Rhetoric of Biological Race Realism
Refreshments served at 3:15 p.m.

Biological race realism is frequently assumed in scientific investigations into presumed connections between race and physical and psychological features such as intelligence, temperament, criminality, and athleticism. I analyze ways scientists and philosophers actively cultivate ignorance surrounding biological race science by using rhetorical tools to portray critiques of biological race realism as in opposition to science itself. These rhetorical strategies involve painting substantive scientific criticisms—such as questions about empirical and methodological issues with data interpretation, unjustified background assumptions, and failure to rule out alternative explanations of data—as motivated purely by ideological concerns. These rhetorical strategies invoke an assumed distinction between epistemic and non-epistemic values in science and misrepresent criticisms of biological race realism as existing wholly outside the realm of epistemic values.

4:40 pm:
Speaker: Bob Lysak, University of Minnesota
Subject: To be announced.

Monday, December 4th 2017
12:15 pm:
Speaker: Larry Rudnick, UMN

Wednesday, December 6th 2017
08:00 am:
Untitled in Physics
1:25 pm:
Speaker: Mark Bowick, KITP, Santa Barbara

What determines shape? Energy minimization in flexible systems with competition between order and shape change can lead to a wide variety of shapes including highly faceted singular structures. I will discuss the of molecularly-thin vesicles with liquid crystalline order.

Faculty Host: Boris Shklovskii

Thursday, December 7th 2017
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Renee Frontiera, University of Minnesota
Subject: To be announced.
Speaker: Sharan Banagin and Claudia Scarlata
3:35 pm:
Speaker: Mark Bowick, KITP Santa Barbara
Subject: Fragile Objects: The Hard Science of Soft Matter

The natural and synthetic world has an extremely rich variety of states of matter. Many of these are fragile structures that are both flexible and complex and they range from atomic in scale to the very large. I will present four vignettes from the world of fragile objects (soft matter) that illustrate their counter-intuitive behavior and the intellectual challenge they present. I will demonstrate how the concept “state of matter” is often not as simple as one might think and show how fluctuations can lead to rather surprising behavior.

Faculty Host: Boris Shklovskii

Friday, December 8th 2017
Speaker: Matthew Johnson (Perimeter Institute and York University)
Subject: TBA
Speaker: Jeremy Webb, Indiana U
Refreshments to be served in the MIfA Interaction Area (Tate 285-11) following the colloquium.
Faculty Host: Liliya L.R. Williams
Speaker: Andy Bruno
Subject: Eurasianism in Soviet Science: The Environmental Views of Aleksandr Fersman
Refreshments served at 3:15 p.m.

Thoroughly a product of imperial Russia’s aristocratic culture, the mineralogist and geochemist Aleksandr Fersman rose to the top of the country’s scientific establishment after the Bolsheviks took control. He then remained a staunch supporter of various industrial projects through much of the Stalinist period. This talk puts Fersman’s thinking about the natural world in conversation with a quite distinctive mode of intellectual inquiry that developed contemporaneously. Eurasianism was a philosophical doctrine of a group of Russian émigrés who emphasized Russia’s unique status straddling Europe and Asia. While Fersman did not belong to this group of thinkers, a number of his ideas drew on specific experiences in the environments of the Eurasian landmass. Indeed, I argue that Fersman’s dualistic understanding of nature, his advocacy for the field of geochemistry, his definition of deserts, and a scheme he proposed for industrial operations owed much to the Eurasian settings of the science he practiced. Furthermore, this case of a Eurasian mineralogist illuminates novel aspects of the interplay between national and global sciences.

4:40 pm:
Speaker: To be announced.

Monday, December 11th 2017
12:15 pm:
Speaker: Patrick Kelly, UMN

Wednesday, December 13th 2017
Speaker: Wolfram Brenig, Technical University Braunschweig

Mott insulators with strong spin orbit coupling have become a testbed for exotic quantum phases, spin liquids and emergent Majorana matter. In this context we present results for the thermal conductivity of the Kitaev-Heisenberg model on ladders and the Kitaev model on honeycomb lattices. In the pure Kitaev limit, and in contrast to other integrable spin systems, the ladder represents a perfect heat insulator. This is shown to be a direct fingerprint of fractionalization into mobile Majorana matter and a static Z2 gauge field. We
find a full suppression of the Drude weight and a pseudogap in the conductivity. With Heisenberg exchange, we find a crossover from a heat insulator to conductor, due to recombination of fractionalized spins into triplons. Increasing the dimension, and for the 2D honeycomb lattice, we show that very similar behavior occurs with however dissipative heat transport resulting in the thermodynamic limit. Our findings rest on several approaches comprising a mean-field theory, complete summation over all gauge sectors, exact diagonalization, and quantum typicality calculations.

Faculty Host: Natalia Perkins

Friday, December 29th 2017
2:00 pm:
Thesis Defense in M10 library
Speaker: Pamela Sooriyan, University of Minnesota
Subject: Dose enhancement in bone due to the 16O(γ,n)15O reaction
This is the public portion of Ms. Sooriyan's thesis defense. Her thesis advisor is John Broadhurst.

External beam radiation therapy is the most common option in the treatment of malignant tumors. It mainly uses Bremsstrahlung photons produced when highly accelerated electrons are incident on a target of high atomic number, gamma rays produced by radionuclides, and electrons beams. In the mega-voltage range of photon beams, the dose absorbed by the tumor is primarily by the incident photons losing their energy to the tissues of the tumor by Compton scattering and pair production. Enhancing photonuclear disintegrations offers the possibility of increasing the dose to the tumor (for the same delivered dose) by introducing secondary charged particles in the irradiated region.
The dose delivered by secondary charged particles from the 16O(γ,n)15O reaction in bone was measured in an attempt to explore the feasibility of local dose enhancement due to photo nuclear disintegrations.

For an externally delivered dose of 13 Gray, the additional dose due to positrons was measured to be 0.18 mGray in bone and 0.025 mGray in tissue, using a photon beam that had about 1.3% of photons of energy needed to initiate the 16O(γ,n)15O reaction.


Wednesday, January 17th 2018
1:25 pm:
Speaker: Jeff Derby (CEMS)
Subject: TBD
Faculty Host: Paul Crowell

Wednesday, January 24th 2018
1:30 pm:
Speaker: Fiona Burnell (University of Minnesota)
Subject: TBD
Faculty Host: Paul Crowell

Thursday, January 25th 2018
Speaker: TBD
Subject: TBD

Friday, January 26th 2018
Speaker: Jorn Kersten (Bergen U., Norway)
Subject: TBA

Wednesday, January 31st 2018
1:30 pm:
Speaker: Sergey Frolov (Pittsburgh)
Subject: Quantum dot chains as emulators of topological superconductors

Tunneling spectroscopy measurements on one-dimensional superconducting hybrid materials have revealed signatures of Majorana fermions which are the edge states of a bulk topological superconducting phase. We couple strong spin-orbit semiconductor InSb nanowires to conventional superconductors (NbTiN, Al) to obtain additional signatures of Majorana fermions and to explore the magnetic-field driven topological phase transition. Specifically, we map out the phase diagram of the topological phase in the space of Zeeman energy and chemical potential, and investigate the apparent closing and re-opening of the superconducting gap. We investigate how the topological superconducting phase would manifest in finite size systems, by electrostatically splitting the wire into segments of varied length. By chaining up several segments of a nanowire, we are realizing a quantum simulator of the Kitaev chain with tunable on-site energies and couplings between the sites, a step towards quantum simulation with semiconductor nanostructures.

Faculty Host: Vlad Pribiag

Thursday, February 1st 2018
Speaker: TBD
Subject: TBD

Friday, February 2nd 2018
Speaker: Liliana Velasco-Sevilla (Bergen U., Norway)
Subject: TBA

Wednesday, February 7th 2018
1:30 pm:
Speaker: Cristian Batista (Tennessee)
Faculty Host: Natalia Perkins

Thursday, February 8th 2018
Speaker: Cristian Batista (Tennessee)
Subject: TBD
Faculty Host: Natalia Perkins

Friday, February 9th 2018
Speaker: TBA
Subject: TBA

Wednesday, February 14th 2018
1:30 pm:
Speaker: Damjan Pelc (University of Minnesota)
Faculty Host: Paul Crowell

Thursday, February 15th 2018
08:00 am:
Speaker: TBD
Subject: TBD

Friday, February 16th 2018
Speaker: TBA
Subject: TBA

Wednesday, February 21st 2018
1:25 pm:
Speaker: Erez Berg (U of Chicago)
Faculty Host: Rafael Fernandes

Thursday, February 22nd 2018
Speaker: Erez Berg (University of Chicago)
Subject: TBD
Faculty Host: Paul Crowell

Friday, February 23rd 2018
Speaker: TBA
Subject: TBA

Wednesday, February 28th 2018
Speaker: Antoine Georges (College de France & Simons Foundation)
Subject: To be announced.
Faculty Host: Martin Greven
4:30 pm:
See Joint Quantum Materials & Condensed Matter Seminar on Thursday this week only.

Thursday, March 1st 2018
Speaker: Joint Colloquium with Earth Sciences (Nier Lecture)
Subject: Exoplanets
Speaker: Sara Seager, MIT

Friday, March 2nd 2018
Speaker: TBA
Subject: TBA

Thursday, March 8th 2018
Speaker: TBD
Subject: TBD

Friday, March 9th 2018
Speaker: TBA
Subject: TBA

Thursday, March 15th 2018
Subject: There will be no colloquium this week due to Spring Break

Friday, March 16th 2018
SPRING BREAK - No seminar this week

Wednesday, March 21st 2018
1:25 pm:
Speaker: Pablo Jarillo-Herrero, MIT
Subject: TBD
Faculty Host: Vlad Pribiag

Thursday, March 22nd 2018
Speaker: Pablo Jarillo-Herrero (MIT)
Subject: TBD
Faculty Host: Paul Crowell

Friday, March 23rd 2018
Speaker: TBA
Subject: TBA

Wednesday, March 28th 2018
1:30 pm:
Speaker: Paul Canfield (Iowa State)
Subject: TBD
Faculty Host: Martin Greven

Thursday, March 29th 2018
Speaker: TBD
Subject: TBD

Friday, March 30th 2018
Speaker: TBA
Subject: TBA

Thursday, April 5th 2018
Speaker: TBD
Subject: TBD

Friday, April 6th 2018
Speaker: TBA
Subject: TBA

Thursday, April 12th 2018
Speaker: TBD
Subject: TBD

Friday, April 13th 2018
Speaker: TBA
Subject: TBA

Wednesday, April 18th 2018
1:30 pm:
Speaker: Ali Yazdani (Tentative)
Faculty Host: Paul Crowell

Thursday, April 19th 2018
Speaker: Ali Yazdani (Princeton University)
Subject: TBD
Faculty Host: Paul Crowell

Friday, April 20th 2018
Speaker: TBA
Subject: TBA

Thursday, April 26th 2018
Speaker: TBD
Subject: TBD

Friday, April 27th 2018
Speaker: TBA
Subject: TBA

Thursday, May 3rd 2018
Speaker: TBD
Subject: TBD

Friday, May 4th 2018
Speaker: TBA
Subject: TBA

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