Condensed Matter and CAM Seminars

Our condensed matter seminars are held on Tuesdays at 3:30pm in CP-179, unless otherwise noted below. Please contact the organizers if you would like to meet with a visitor. The CM and CAM seminar series are organized by Doug Strachan and Joe Straley.

This week

April 17

Jeremy Van Cleve and Taylor Kessinger (UK).
" (UK Biology). Host: Kaul
" Quantitative models for the evolution of stochastic switching and tunneling through fitness valleys "

First, we'll discuss how organisms face a difficult trade-off when the future is uncertain. They can either specialize on a single phenotype across a range of environments, hedge their bets by randomly choosing among a set of phenotypes, or invest in physiological machinery to adjust their phenotype plastically. Understanding the evolutionary relationship between these strategies remains a puzzle. Here, we present a simple model for the evolution of specialization, bet-hedging, and plasticity that reveals how these strategies are fundamentally sensitive to the shape of the cost of plasticity. When costs accelerate with plasticity, bet-hedging is the likely outcome. In contrast, decelerating costs can lead to full adaptive plasticity, but only when initial conditions are right. The shape of the cost curve is due to the genetic and metabolic network machinery underlying plastic traits, which means that certain networks are more likely than others to evolve plasticity.

Second, we'll talk about how organisms must often cross "fitness valleys", moving through regions of lower fitness in order to find higher peaks. These valleys can be crossed by sequential fixation of mutations, multiple mutations occurring simultaneously, or "tunneling", a process in which transient lower-fitness subpopulations persist for short times, affording a time window in which a complex adaptation can appear and establish. In many organisms of interest where adaptation is rapid, including many pathogens, the fate of a new mutation depends on its genetic background and is governed not by a process called genetic draft. Using computer simulations, we characterize the rate at which valley crossing occurs in rapidly adapting asexual populations. We find that the average time to cross a shallow valley can be much longer than in case when adaptation is less rapid. However, the crossing time almost does not depend at all on either the depth of the valley or the height of the peak (i.e., the deleterious effect of the intermediate state or the beneficial effect of the full adaptation). Rapidly adapting populations therefore cross deeper valleys at a higher relative rate compared to populations with low fitness variance: complex adaptations reached by leaping across a rugged landscape may be the rule, not the exception.

Schedule for Fall 2017 - Spring 2018

Nov. 14 Chris Richards (Department of Chemistry, UK). Host: Strachan
abstract

Dec. 5 Marcelo I. Guzman (Department of Chemistry, UK). Host: Strachan
Probing Interfacial Chemistry: Heterogeneous Oxidations in the Environment

January 16 Joseph Straley (UK).
" Wakes and waves on lakes and on the Fermi sea "

I will describe how the wave pattern behind a moving ship arises from the solutions to the wave equation, and the applications to arbitrary dispersion relations.

January 23 Julia Wildeboer (UK).
" "

January 30 Julia Bursten (UK).
" "

February 6 John Connell (UK).
" Hydrogenated Thin-film Ferroelectrics: New Transparent Conducting Oxides? "

Abstract

February 13 Luiz Henrique Santos (U. Illinois). Host: Kaul
" Chern-Simons Composite Fermion Theory of Fractional Chern Insulators "

Abstract

February 20 Maryam Souri (UK). Host: Seo
Abstract

February 27 March Meeting Previews (UK). Host: Straley
Save airplane fare to Los Angeles! The very best of the talks will be presented right here!

  • Maryam Shahi
    "Transverse Thermal Diffusivity of Polymer and Small Molecule Organic Semiconductors Measured with an ac-Photothermal Technique."
    Abstract
  • Ankur Das
    "Phase Transition of SU(N) x U(1) Theory with M Fundamental Bosons"
    Abstract
  • Amartya Saha
    "Edge Reconstruction in Monolayer Graphene at and near nu = 0"
    Abstract
  • Nisheeta Desai
    "Quantum phases of SU(N) spins on a BCC lattice">
    Abstract

March 20
No seminar

March 27
TBA

April 3 Rick Honaker (UK Mining Engineering). Host: Straley
" Production of Critical Rare Earth Element Concentrates from Coal Sources"
abstract

April 10 Yang-Tse Cheng (UK). Host: Straley

Seminar schedules from past semesters are archived here

This page is maintained by Joe Straley