Search Talks

Motivated by recent interesting holographic results, several attempts have been made to study complexity ( rather " Circuit Complexity") for quantum field theories using Nielsen's geometric method. But most of the studies so far have been limited to free quantum field theory. In this talk we will take a baby step towards understanding the circuit  complexity for interacting quantum field theories. We will consider \lambda \phi^4 theory and discuss in detail how to set up the computation perturbatively in coupling. Our method enables us to study circuit complexity in the epsilon expansion for the Wilson-Fisher fixed point. We find that with increasing dimensionality the circuit depth increases in the presence of the \phi^4 interaction eventually causing the perturbative calculation to breakdown. We discuss how circuit complexity relates with the renormalization group. Finally we discuss several possible generalization and compare our results with other approaches.

Using knowledge about the spectrum of operators in N=4 SYM, consistency of OPE, and analytic bootstrap techniques, I will obtain 1- loop corrections for 4-pt functions of single particle half-BPS operators of IIB supergravity on AdS_5\timesS^5. Along the way, I will discuss a general formula for the leading anomalous dimension of all double-trace operators in the supergravity regime.

Recently I pointed out that reconstruction of interior operators can be interpreted as the Hayden-Preskill recovery. Building on this observation, I will propose a resolution of the firewall puzzle by describing a state-independent reconstruction of interior operators which does not lead to the non-local signaling. 

We show how the extended thermodynamics of hyperbolic black holes in AdS describes features of quantum information measures in quantum field theory, and discuss prospects for making further connections. In particular, the second law of thermodynamics is seen in this context to map to the generalized Zamolodchikov c-theorem, connecting these two firmly for the first time. Some projects for getting further lessons and perhaps new tools from  these connections (perhaps using holographic heat engines) are outlined. 

While the simplest Feynman diagrams evaluate to multiple polylogarithms, more complicated functions can arise, involving integrals over higher-dimensional manifolds. Surprisingly, all examples of such manifolds in the literature to date are Calabi-Yau. I discuss why this is, and prove that a specific class of "marginal" diagrams give rise to Calabi-Yau manifolds. I demonstrate a bound on the dimensionality of these manifolds with loop order, and present infinite families of diagrams that saturate this bound to all orders.

The minimal Standard Model running of the gauge couplings gives us a hint of a Grand Unified Theory (GUT) at M_U ~ 10^14 GeV — a scale, however, too high to probe directly via collider searches. Fortunately, since the inflationary Hubble scale H can be as high as  5 x 10^13 GeV ~ M_U, such GUT scale states can be cosmologically produced during inflation and contribute to primordial non-Gaussianity (NG).

In this talk, I will explore the possibility of doing on-shell, mass-spin spectroscopy of GUT-states by studying such NG contributions in an extra-dimensional framework of orbifold GUTs. I will identify an interesting regime where the extra dimension is stabilized close to the onset of a horizon and find that the KK gravitons and KK gauge bosons can mediate observable NG providing a direct probe of orbifold GUTs.

Axion-like particles are a broad class of dark matter candidates which are expected to behave as a coherent, classical field with a weak coupling to photons. Research into the detectability of these particles with laser interferometers has recently revealed a number of promising experimental designs. Inspired by these ideas, we propose the Axion Detection with Birefringent Cavities (ADBC) experiment, a new axion interferometry concept using a cavity that exhibits birefringence between its two, linearly-polarized laser eigenmodes. This experimental concept overcomes several limitations of the designs currently in the literature, and can be practically realized in the form of a simple bowtie cavity with tunable mirror angles. Our design thereby increases the sensitivity to the axion-photon coupling over a wide range of axion masses.

Anomaly cancellation conditions place strong constraints on many physical theories. In the traditional framework, local and global anomalies are detected by computing an eta invariant of a certain Dirac operator on a mapping torus. Recent research has uncovered the existence of finer anomaly cancellation conditions, not visible in these traditional settings. I will review the traditional and refined anomalies, and apply them to various symmetries of interest in particle physics. Examples include the (various global forms of) the Standard Model, GUT's, and discrete gauge symmetries of physical interest such as proton triality and a certain Z4 symmetry in the (MS)SM.

The Twin Higgs model is an attractive solution to the little Hierarchy problem with top partners that are neutral under SM gauge charges. The framework is consistent with the null result of LHC colored top partner searches while offering many alternative discovery channels. Depending on model details, the phenomenology looks very different: either spectacular long-lived particle signals at colliders, or a plethora of unusual cosmological and astrophysical signatures via the existence of a predictive hidden sector. I will examine the latter possibility, and describe how the asymmetrically reheated Mirror Twin Higgs provides a predictive framework for a highly motivated and highly non-trivial interacting dark sector, with correlated signals in the CMB, Large Scale Structure, and direct detection searches, as well as higgs precision measurements at colliders. This provides a vivid example of the collider-cosmology complementarity, and motivates a variety of new astrophysical searches that are motivated by the hierarchy problem.

In many-body chaotic systems, the size of an operator generically grows in Heisenberg evolution, which can be measured by certain out-of-time-ordered four-point functions. However, these only provide a coarse probe of the full underlying operator growth structure. We develop a methodology to derive the full growth structure of fermionic systems, that also naturally introduces the effect of finite temperature. We then apply our methodology to the SYK model, which features all-to-all q-body interactions. We derive the full operator growth structure in the large q limit at all temperatures. We see that its temperature dependence has a remarkably simple form consistent with the slowing down of scrambling as temperature is decreased. Furthermore, our finite-temperature scrambling results can be modeled by a modified epidemic model, where the thermal state serves as a vaccinated population, thereby slowing the overall rate of infection.

Motivated by the problem of defining the entanglement entropy of the graviton, we study the division of the phase space of general relativity across subregions. Our key requirement is demanding that the separation into subregions is imaginary---i.e., that entangling surfaces are not physical. This translates into a certain condition on the symplectic form. We find that gravitational subregions that satisfy this condition are bounded by surfaces of extremal area. We characterise the 'centre variables' of the phase space of the graviton in such subsystems, which can be taken to be the conformal class of the induced metric in the boundary, subject to a constraint involving the traceless part of the extrinsic curvature. We argue that this condition works to discard local deformations of the boundary surface to infinitesimally nearby extremal surfaces, that are otherwise available for generic codimension-2 extremal surfaces of dimension ≥ 2.