The CTP Lunch Club meets every Friday at noon in the Cosman seminar room, 6C-442 (provided that there are sufficient speakers). Pizza will be provided.
The seminars are designed for graduate students and should be accessible to all students. First year students are particularly encouraged to attend so that they may learn about research being performed in the CTP. The goal is learning, and to encourage participation, the seminars will be for students only.
Email notification of the club will be sent to the ctp-all, ctp-postdocs and ctp-students email lists as appropriate. If you wish to speak, or have suggestions about speakers and/or possible workshop topics, please contact the organizers, Anand Natarajan at anandn-at-mit[dot]edu and Srivatsan Rajagopal at srivat91-at-mit[dot]edu.
Duality and Dynamics of a Stabilized Radion
In the wake of the Higgs discovery, exploring the nature of electroweak symmetry breaking, and in particular the apparent hierarchy between weak and gravitational scales, has become a priority. The extra dimensional models of Randall and Sundrum (RS) address the hierarchy problem geometrically and, through the AdS/CFT correspondence, are related to a broader class of models that employ conformal symmetry in physics beyond the standard model (SM). In this talk we will explore the duality between the most realistic realization of the RS scenario (that is, when the stabilization of the extra dimension is carefully taken into account and SM fields propagating in the extra dimension) and models with conformal dynamics. In doing so, we determine how the familiar identification of the parameters on the two sides of the AdS/CFT correspondence is modified in the presence of couplings of the bulk Standard Model fields to the field that stabilized the extra dimension.
On robust forms of quantum entanglement
The classical PCP theorem [ALMSS, D] is arguably one of the most important discoveries in CS theory in the last 20 years, showing that that verifying a proof need not be a meticulous pain-staking task it is perceived to be, but can amount to a simple probabilistic, and very local examination of the bits of the proof. Several years ago, researchers in quantum computing have tried to pose a similar question for quantum "proofs": can the verification of a ground-state of a local Hamiltonian system be done probabilistically and locally in a similar fashion.
Despite some progress on variants of this question, we still do not even know in which way to conjecture a statement for a quantum PCP: is it possible, or is it not possible. Still, this question, while intriguing on it's own, has motivated exploration of various forms robust entanglement, ranging from quantum locally testable codes, to local Hamiltonians that support entanglement at "room temperature".
In this talk, I will describe the different formulations of the conjecture, and survey some of the recent results in the field.
New Experimental Searches for Dark Matter through the study of Boosted Dark Matter
In this talk, I will discuss novel thermal dark matter (DM) scenarios where present- day annihilation of DM in the galactic center produces boosted stable particles in the dark sector. Due to their large Lorentz boost, these particles can be detected in large volume terrestrial experiments such as Super K. I will cover the reach of a particular model of boosted DM in neutrino experiments as well as the current constraints.
One of the most intriguing consequences of the Higgs boson discovery is that its mass places the Standard Model near the border between absolute stability and metastability, i.e. our universe is unstable, but should last for an astronomically long time. This conclusion is based on effective potential calculations which involve some suspicious elements: for example, the stability criteria depends on gauge. Can we establish the fate of our universe using only self-consistent methods?
Aspects of Symmetry, Topology and Anomalies in Quantum Matter
Many-body quantum matter can have entanglement, such that the wavefunction of a whole system cannot be deformed to a trivial product state under local unitary transformations - due to the symmetry-protection or the long range entanglement. This implies that Ginzburg-Landau theory's approach on distinguishing phases of matter by symmetry-breaking is only a semi-classical picture, not a complete quantum story. Beyond the Ginzburg-Landau's paradigm, there are distinct phases of quantum matter emergent from the interplay of symmetry, topology and anomalies. Here I will focus on the bulk gapped phases of Symmetry-Protected Topological states (SPTs) and Topological Orders.
In this talk, I will provide the insight between the bulk topological phases and their boundary anomalies. In light of SPTs and their gauge anomalies, we can: (1) bypass fermion-doubling theorem, to design a non-perturbative lattice model which realizes chiral fermion/chiral gauge theories at low energy, (2) realize bosonic anomalies with discrete symmetries. In light of topological orders and their exotic statistics, we find: (3) The 3+1 dimensional bulk of topological orders can support exotic multi-string braiding whose pattern is in the form of mathematical knot and link.
Anomalies and Symmetry Protected Topological states
Nonperturbative QCD in nuclear and particle physics
The nonperturbative nature of the strong interaction plays a critical role in many aspects of forefront nuclear and particle physics. I will illustrate this through a series of vignettes relevant at various different energy scales. QCD calculations of hadronic observables are central to our current understanding of the Standard Model where they are an essential ingredient in the extraction of many of the SM parameters. Control of QCD is also important in many searches for physics beyond the standard model that are conducted using hadronic or nuclear targets. At low energies, QCD (along with the electroweak interactions) is also responsible for the structure and interactions of nuclei and very recently we have been making inroads into describing the complex realm of nuclei from the underlying theory. Finally, strongly interacting gauge theories provide possible candidates for dark matter and the computational tools developed for QCD allow investigations of potentially novel dynamics in such models.
Little String Amplitudes (and the Unreasonable Effectiveness of 6D SYM)
I’ll briefly introduce 6D little string theory (LST) and its double scaled version (DSLST). Then I’ll discuss the holographic dual type II worldsheet string theory and its connection to 6D maximal super Yang-Mills theory which describes a low energy sector of the 6D little string theory. I’ll explain the striking agreements we found between 6D SYM Cartan gluon loop-level amplitudes and type II string theory tree-level amplitudes and outline the procedure in obtaining the results.
Soft Theorems from Effective Theory
The study of the limiting behavior of the S-matrix as external particles become soft has a long and illustrious history and has deep consequences for physics at long distances. In this talk, I will review the soft theorems of gauge theory and gravity and utilize effective theory methods to provide all-orders understanding of the soft limit.
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