Theory Seminar

Seminars are at 2pm in Room 179 CP Building unless otherwise indicated.

Hall transport, angular momentum and Ward identities.

Recently, unexpected relations between unrelated physical quantities such as Hall viscosity, conductivity and angular momentum have been proposed for certain condensed matter systems with broken parity. We derive the quantum field theory Ward identities originated from area preserving as well as conformal transformations for relativistic as well as non-relativistic systems. The relations among these physical quantities depend on the symmetries of the system. A special cases yields the well known relation: Hall viscosity is half the angular momentum.
Date:
-
Location:
CP179
Event Series:
Theory Seminar

Theory Seminar: Relativistic Effective Field Theory and Parity-Odd Transport

We introduce a new 2+1 dimensional topological current that is identically conserved and whose charge is equal to the Euler character of the two dimensional spacelike foliations. The existence of this current allows us to introduce new Chern-Simons-type terms in the effective field theories describing relativistic quantum Hall states and (2+1) dimensional superfluids. In the quantum Hall case, this current provides the natural relativistic generalization of the Wen-Zee term, required to characterize the shift and Hall viscosity in quantum Hall systems. For the superfluid case this term is required to have nonzero Hall viscosity and to describe superfluids with non s-wave pairing.

Date:
-
Location:
CP179
Event Series:
Theory Seminar

Universal Hydrodynamics for Quantum Critical Points with Lifshitz scaling

We formulate a universal hydrodynamic description for theories without boost invariance, a non-trivial extension of Landau and Lifshitz. New transport coefficients, one in neutral and two more in charged fluids, are uncovered. We provide verifiable experimental consequences. While the description is applicable for the Lorentz (or Galilean) invariant theories with broken boost invariance, we focus on its application to quantum critical theories with Lifshitz scaling
symmetry.
 
The talk should be of general interest.  All are welcome to attend.
 
Date:
-
Location:
CP179
Event Series:
Theory Seminar

Time Dependent Holography

    One of the most important results emerging from string theory is the gauge gravity
duality (AdS/CFT correspondence) which tells us that certain problems in particular
gravitational backgrounds can be exactly mapped to a particular dual gauge theory
a quantum theory very similar to the one explaining the interactions between funda-
mental subatomic particles. The chief merit of the duality is that a difficult problem
in one theory can be mapped to a simpler and solvable problem in the other theory.
The duality can be used both ways.
     Most of the current theoretical framework is suited to study equilibrium systems,
or systems where time dependence is at most adiabatic. However in the real world,
systems are almost always out of equilibrium. Generically these scenarios are de-
scribed by quenches, where a parameter of the theory is made time dependent. In
this dissertation I describe some of the work done in the context of studying quantum
quench using the AdS/CFT correspondence. We recover certain universal scaling
type of behavior as the quenching is done through a quantum critical point. Another
question that has been explored in the dissertation is time dependence of the gravity
theory. Present cosmological observations indicate that our universe is accelerating
and is described by a spacetime called de-Sitter(dS). In 2011 there had been a spec-
ulation over a possible duality between de-Sitter gravity and a particular field theory
(Euclidean SP(N) CFT). However a concrete realization of this proposition was still
lacking. Here we explicitly derive the dS/CFT duality using well known methods in
field theory. We discovered that the time dimension emerges naturally in the deriva-
tion. We also describe further applications and extensions of dS/CFT.

 

Date:
-
Location:
CP171
Event Series:
Theory Seminar
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