Events at 402 Classroom, Physics South, UCB-Campus

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Abstract: Axion dark matter which couples to fermions can act as an effective magnetic field, the “axion wind”, inducing spin precession in condensed matter systems. I will describe a new proposal for axion wind detection using an unusual phase of superfluid helium-3, the homogeneous precession domain (HPD). In the HPD, spins precess coherently over a macroscopic volume even in the … Read More

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Heavy axions can arise in the context of Grand Unified theories where a confining dark gauge group unifies with the Standard Model (SM) gauge group. Depending on the strength of the axion coupling to the SM, heavy axion lifetimes can vary drastically, requiring very different observational probes. I will discuss two such probes. First, I will show heavy axions with MeV … Read More

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Abstract:  “In the non-relativistic limit, scattering of two particles by boson exchange can be described using a static potential, i.e, that of a force between them. The exchange of two fermions can also lead to a force, as if the two fermions behave like an effective boson. These forces are called “quantum forces”, and the range of these forces is … Read More

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Abstract: In work to appear with Ballin-Creutzig-Dimofte, we constructed vertex operator algebras associated to A and B twists of 3d N=4 abelian gauge theories. These are boundary VOAs supported on holomorphic boundary conditions of Costello-Gaiotto. For the B twist, the vertex algebra V_B is a simple current extension of an affine Lie superalgebra, and using the work of Creutzig-Kanade-McRae, we … Read More

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In a landmark work, Frances Kirwan described the relation between the cohomology of a GIT quotient of a smooth projective variety X and the equivariant cohomology of X by what is known as the ‘subtraction method’: this relies on the equivariant perfection of the destabilizing stratification of X. Later work geared toward describing the cohomology ring structure relied on Poincare … Read More

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Abstract: The idea that spacetime may be discrete in the UV, possibly at the Planck scale, has been fraught with issues due to generically strong effects of such discreteness on the flow of a quantum field theory down to the IR. Nevertheless, recent work on two dimensional models of holography seem to provide an example of the emergence of spacetime from … Read More