Theory Seminar

Directions for Particle Physics Beyond Asymptotic Freedom

In recent years, new theories of particle physics have been discovered whose short-distance behaviour is controlled by an interacting (rather than a free) UV fixed point. The very existence of these asymptotically safe particle theories has opened up new directions to UV-complete the Standard Model of particle physics beyond the paradigm of asymptotic freedom. In this talk, I give a systematic overview of QCD-like theories with weakly and strongly coupled fixed points, with and w/o supersymmetry, and discuss key features. Concrete applications for BSM physics are also given. If time permits, I briefly outline how some of these ideas and insights are used to understand the quantisation of gravity.
 
Date:
Location:
CP 179 (Notice special date)

The Charm Mission into Flavor and BSM

The charm sector provides new and unique insights into flavor and BSM physics, complementing longstanding programs with kaons and B-mesons. We report status and  progress in null test searches from theory on rare decays of charm mesons and baryons into invisibles, photons and leptons, and where flavor experiments are currently pushing this frontier. We also discuss CP-violation together with sizable U-spin violation seen in hadronic 2-body decays at the LHCb-experiment. A stunning explanation of this puzzle is given by a light, hadrophilic Z-prime that can also resolve issues with the pion-form factor in J/psi-decays.

 

Date:
Location:
CP 179
Event Series:

Theory/String Seminar: A fresh look at the large N limit of matrix models and holography

Abstract: We will discuss some known subtleties of emergent geometries from large N theories (why they are different from our normal expectation for a continuum spacetime) and discuss a way to address them. We will use matrix models as our main example. The primary tool will be an exact bosonization of nonrelativistic fermions that was discovered some time ago. 
Date:
Location:
CP 303

Theory/String Seminar: A fresh look at the large N limit of matrix models and holography

Abstract: We will discuss some known subtleties of emergent geometries from large N theories (why they are different from our normal expectation for a continuum spacetime) and discuss a way to address them. We will use matrix models as our main example. The primary tool will be an exact bosonization of nonrelativistic fermions that was discovered some time ago. 
Date:
Location:
CP 303

Probing Strong Nucleon-Nucleon Interactions at Short Distance

Among the four known fundamental forces or interactions, gravitation and electromagnetism are close to daily life, while the strong and weak forces only reveal themselves at sub-atomic or smaller scales. The strong force, which is mediated by gluon exchange between quarks confines quarks into protons and neutrons (nucleons). The residual component of this strong force that induces the strong nuclear interactions between nucleons at the fermi scale (10^-15m). This so-called "nuclear force" is attractive at a longer distance (e.g. for nucleon separation greater than the proton radius) and binds nucleons together into nuclei), while the force is strongly repulsive at a much shorter distance which prevents the nucleus from collapsing.  Nucleon interactions at short distances are not well-described in either QCD or the field theory. Experimentally, a series of electron-nucleon scattering measurements at Jefferson Lab (JLab) have determined about 20% of nucleons in heavy nuclei are moving fast (above the Fermi momentum) due to hard, short-distance interactions with another nucleons, forming so-called short-range correlated (SRC) pairs. Understanding those SRC pairs is necessary in providing a complete  description of nuclear structure. It also offers us a unique chance to probe the tensor and repulsive force at intermediate to short distances. In this talk, I will present recent results from the JLab Hall A tritium program which studied the momentum distribution, and spin/isospin structure of SRC pairs in the mirror nuclei tritium and helium-3. I will then discuss how those measurements help us better understand the short-distance part of strong nucleon-nucleon interactions, and their connections to future experiments.
Date:
Location:
Zoom
Event Series:

Quantum Computing with Continuous Variables

NOTE SPECIAL TIME AND LOCATION

ABSTRACT: Quantum fields are fundamental constituents of the physical world. The encoding of quantum information in continuous-variable (CV) quantum fields, a.k.a. qumodes (in lieu of discrete-variable qubits), has enabled multipartite entanglement over millions of qumodes. This scale, unparalleled in any qubit architecture, defines new horizons and paradigms to be explored for quantum computing, quantum communication, and quantum sensing. I will outline our work in CV quantum computing applied to quantum field theory and quantum machine learning aiming at understanding properties of physical systems.

Date:
Location:
CP 303
Event Series:

Effective Field Theories for precision beta decays

Beta decays have been instrumental in establishing the Standard Model as the theory of the electroweak interactions. In the era of the Large Hadron Collider, beta decays still provide very sensitive probes of physics beyond the Standard Model, which are highly competitive and complementary to searches at the energy frontier.For example, recent tensions in tests of the unitarity of the first row of the Cabibbo-Kobayashi-Maskawa quark mixing matrix might point to new physics at scales of about 10 TeV, still beyond the reach of the LHC.Because of the increasing experimental accuracy, advances in hadronic and nuclear theory are crucial to fully exploit beta decays as probes of new physics. In this talk, I will discuss the advantages of organizing various contributions to beta decays using effective field theories (EFTs). After discussing the EFT setup, I will review its application to neutron decay and to the calculation of the beta spectrum in the decay of 6He.
 
Date:
Location:
Zoom
Event Series:

How are we saved from complete annihilation

Historically it was both a surprise and a theoretical triumph to find out that anti-matter exists at all. As we learnt more about the Universe, we are surprised by something very different - why do we almost exclusively see matter. The fact that throughout most of human history, we were oblivious to the existence of anti-matter is a testament to the dominance of matter over anti-matter. Looking at the earliest light and earliest elements in the Universe, we find that this imbalance goes back to at least when the Universe was a mere second old. However, inflation would wipe out any difference between matter and anti-matter and all processes we know of cannot create such an asymmetry. I will review the three main answers physicists have given to this fundamental question and what challenges face the community trying to shed light on this issue.
 
Date:
Location:
Zoom
Event Series:

IR Phase of Thermal QCD, Non-Analytic Dirac Spectra and Emergent Dimensions

 Recent suggestion that SU(3) gauge theories with fundamental quarks generate a phase with IR scale invariant glue leads to interesting consequences materializing in very unusual ways. In this talk I will discuss these developments, including those featured in the Title.

Date:
Location:
Zoom
Event Series:

(UV-complete) Emergent Matrix Cosmology

I will review recent results, and list outstanding challenges, of deriving an emergent spacetime from a non-perturbative proposal of String Theory -- namely, the BFSS matrix model. I will show how a metric can be coarse-grained from abstract matrix degrees of freedom, and how one naturally gets a scale-invariant spectrum of primordial perturbations in this model without introducing arbitrary tunable parameters. Furthermore, I will highlight distinct cosmological signatures of this model which have the potential of distinguishing it from other early-universe paradigms.

 

Date:
Location:
Zoom
Event Series: