Search Talks

Axion cosmic strings have for some time been considered a potential source of enhancement of axion dark matter production, and have been the subject of extensive simulations (for references, see out in recent years).  But axion strings are rather peculiar entities.  This talk will explore some aspects of these objects, and suggest that they are not likely to play a distinguished role in early universe cosmology.

Detection mechanisms for low mass bosonic dark matter candidates, such the axion or hidden photon, leverage potential interactions with electromagnetic fields, whereby the dark matter (of unknown mass) on rare occasion converts into a single photon. Current dark matter searches operating at microwave frequencies use a resonant cavity to coherently accumulate the field sourced by the dark matter and a near standard quantum limited (SQL) linear amplifier to read out the cavity signal. To further increase sensitivity to the dark matter signal, sub-SQL detection techniques are required. Here we report the development of a novel microwave photon counting technique and a new exclusion limit on hidden photon dark matter. We operate a superconducting qubit to make repeated quantum non-demolition measurements of cavity photons and apply a hidden Markov model analysis to reduce the noise to 15.7 dB below the quantum limit, with overall detector performance limited by a residual background of real photons. With the present device, we perform a hidden photon search and constrain the kinetic mixing angle to  ≤ 1.68×10−15 in a band around 6.011 GHz (24.86 μeV) with an integration time of 8.33 s. This demonstrated noise reduction technique enables future dark matter searches to be sped up by a factor of 1300. By coupling a qubit to an arbitrary quantum sensor, more general sub-SQL metrology is possible with the techniques presented in this work.

I will discuss the conditions satisfied by the 2 → 2 scattering amplitude in unitarity and causal theories, presenting a simple formulation in term of moments of a positive measure. I will identify complete subsets of two-sided constraints, suitable to bound Effective Field Theories (EFTs) at any finite order in the energy expansion. I will also discuss  the importance of IR loop effects on these bounds. A consequence of this study is that EFTs in which the scattering amplitude in some regime grows in energy faster than E6 (e.g. higher spin particles with masses smaller than their inverse size) cannot be UV-completed.

We will describe an approach to the theory of fundamental particlesbased on finite-dimensional quantum algebras of observables. We will explain why the unimodularity of the color group suggests an interpretation of the quarklepton symmetry which involves the octonions and leads to the quantum spaces underlying the Jordan algebras of octonionic hermitian 2 × 2 and 3 × 3 matrices as internal geometry for fundamental particles. In the course of this talk, we will remind shortly why the finite-dimensional algebras of observables are the finite-dimensional euclidean Jordan agebras and we will describe their classifications. We will also explain our differential calculus on Jordan algebras and the theory of connections on Jordan modules. It is pointed out that the above theory of connections implies potentially a lot of scalar particles.

The gravitational coupling of nearby massive bodies to test masses in a gravitational wave (GW) detector cannot be shielded, and gives rise to 'gravity gradient noise’ (GGN) in the detector. In this talk, I will discuss how any GW detector using local test masses in the Inner Solar System is subject to GGN from the motion of the field of 10^5 Inner Solar System asteroids, which presents an irreducible noise floor for the detection of GW that rises exponentially at low frequencies. This severely limits prospects for GW detection using local test masses for frequencies below (few) x 10^{-7} Hz. At higher frequencies, I’ll show that the asteroid GGN falls rapidly enough that detection may be possible; however, the incompleteness of existing asteroid catalogs with regard to small bodies makes this an open question around microHz frequencies, and I’ll outline why further study is warranted here. Additionally, I’ll mention some prospects for GW detection in the ~10 nHz-microHz band that could evade this noise source.

I will review recent progress in application of separation of variables method.

In particular I will review the construction for the integrable spin chains with gl(N) symmetry. 

By finding, for the first time, the matrix elements of the SoV measure explicitly I will show how to compute various correlation functions and wave function overlaps in a simple determinant form. 

General philosophy of application of these methods to the problems related to AdS/CFT, N=4 SYM etc. will be discussed too. 

The talk will focus on the spectrum of near-extremal black holes in gravity and near-BPS black holes in supergravity. For concreteness, we will study cases in asymptotically four-dimensional flat space and three-dimensional Anti-de Sitter. This will be done by analyzing quantum effects near the horizon captured by an emergent Jackiw-Teitelboim mode at low temperatures. This will allow us to systematically study questions such as the extremal degeneracy and the size of the gap in the black hole spectrum, which can be compared to some string theory constructions.

How to deal with diffeomorphism symmetries is one of the difficult problems in general relativity. Because of the diffeomorphism symmetries, we need to consider diffeomorphism invariant operators and gravitational dressing. In this work, we consider a special gravitational dressing which is to locate the operator by shooting geodesic from the spatial boundary. We try to use Peierls bracket to study the commutator between this gravitational dressing operator and the ADM energy operator. We found the ADM energy increase/decrease when the extra created out-going particle is in front of/behind the event horizon. Our result strengthens the Marolf-Polchinski firewall argument in some sense. In the talk, I will first briefly review the Peierls bracket, which is a linear response interpretation of bracket computation in covariant phase space formalism. We also illustrate the Peierls bracket with several examples. After that, we use Peierls bracket to study the Hamiltonian flow of the gravitational dressing operator, from which we can read out the commutator between the gravitational dressing operator with the ADM energy operator.

In this talk I will discuss the universal properties of thermal transport in conformal field theories that are perturbed by a TTbar operator. TTbar-deformation is known to be an exactly solvable deformation in that the spectrum of the undeformed theory alone suffices to predict that of the deformed theory. Unique properties of TTbar deformation allow us to study the TTbar-deformed CFTs using two disparate methods: integrability and holography. I will apply these two approaches to study the non-equilibrium steady states and Drude weights, finding perfect agreement. I will also explain how the integrability-based approach yields the exact momentum diffusion constant, which, to our surprise, also happens to satisfy a universal formula. Finally I will briefly touch upon a curious connection between TTbar-deformed CFTs and an integrable cellular automaton model called the Rule 54 chain.

This talk will be split into two distinct halves: The first half will be based on the paper arxiv:2007.03662 and suggest that an interplay between microscopic and macroscopic physics can lead to an undulation on time scales not related to celestial dynamics. By searching for such undulations, the discovery potential of light DM search experiments can be enhanced.
The second half will look at some currently unpublished work into finding all the semi-simple subalgebras of u(48) which contain the SM. Such algebras (in a loose sense of the term) form GUTs and studying them has relevance to family unification, proton decay etc. Although there has been previous work into the classification of GUTs, we believe this is the first this broad question has been answered.