Upcoming Thesis Defenses

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Adaptive mode matching in advanced ligo and beyond

Mar 26, 2019, 1:00 PM-2:30 PM

Room: 202/204 Physics Bldg.

LIGO was built with the purpose of detecting the ripples in space-time caused by astrophysical events with the hopes of understanding the complexities hidden within the cosmos. In 2011, the primary stages of Advanced LIGO were installed and commissioned to start the first observing run (O1). Following that time, the detectors had hardware replaced in order to mitigate noise from scattered light and new optics which reduced the losses from absorption. The upgrades were in preparation for the third observing run (O3) and the work presented here is primarily focused on experimental techniques for operating at higher power and mode matching Gaussian beams in the dual-recycled Michelson interferometer for the Advanced LIGO era and beyond.

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Holography, large N, and supersymmetry on the lattice by Raghav Jha

Apr 2, 2019, 2:45 PM-4:00 PM

Room: 202 Physics Bldg.

Advisor: Prof. Simon Catterall, Contact: Yudaisy Salomon Sargenton - phyadmin@syr.edu

The lattice studies of strongly coupled gauge theories started with the pioneering work of Wilson. The success of lattice QCD over the decades has improved our understanding of the strong dynamics, crucial for a proper understanding of many interesting phenomena in Physics. However, it is now known that the Standard Model of particle physics is only an approximation to some richer underlying theory. It is believed that supersymmetry has a special role to play in the framework of such a theory. Even if nature is non-supersymmetric at all energy scales and we don’t see any experimental evidence in the coming decades, the beautiful structure of these theories and the great failure could still be very important lessons in our quest to understand the universe. In four dimensions, one particular supersymmetric theory has drastically altered our understanding of the holographic principle. In view of these observations, the study of supersymmetric theories on the lattice at strong couplings is crucial. Even though lattice supersymmetry has a long history going back four decades, it has been very difficult to simulate four-dimensional theory at strong couplings till date. This is because supersymmetry on the lattice is far from being trivial because of the supersymmetric algebra. However, substantial progress has been made in studying these theories on the lattice over the past decade. Several wonderful ideas like topological twisting, Dirac-Kahler fermions, differential forms, point group symmetries of the lattice all come together and has enabled us to study these supersymmetric theories by preserving a subset of supersymmetries exactly on the lattice. In this thesis defense talk, I will discuss numerical studies of super Yang-Mills (SYM) theories in various dimensions with insights about their large N limit and the relation to gauge/gravity dualities. 

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Relevant Operators of Particle Physics and Cosmology

Apr 5, 2019, 10:00 AM-11:30 AM

Room 208 Physics Bldg.

Advisor: Prof. Jay Hubisz, Contact: Yudaisy Salomon Sargenton - phyadmin@syr.edu

Although the Standard Model of Particle Physics can reproduce the results of all the experiments performed to this date, it can only be an effective theory of fundamental physics. However, treating the Standard Model this way brings its own set of challenges; namely, the coefficients of relevant operators become extremely sensitive to UV physics. The relevant operator of the Standard Model is the Higgs mass which causes the "hierarchy problem", while the cosmological constant term of cosmology results in the "cosmological constant problem". In this thesis defense, I will talk about how these issues can guide us in the pursuit of searching for new physics, both from a model building perspective and from a phenomenological perspective. In the first part, I will present a Higgs model on a five-dimensional Anti-de-Sitter space which attempts to make the Higgs criticality a dynamical attractor of the theory, thereby eliminating the sensitivity to the UV parameters. In the second part, I will talk about how we can gain some insights about the cosmological constant problem from the observations of binary neutron star mergers.

 

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Geometric and Topological Aspects of Soft & Active Matter by Suraj Shankar by Suraj Shankar

Apr 10, 2019, 2:00 PM-3:30 PM

Room: 202/204 Physics Bldg.

Advisor: Prof. Cristina Marchetti, Prof. Mark Bowick-Contact: Yudaisy Salomon Sargenton - phyadmin@syr.edu

Topological and geometric ideas are now a mainstay of condensed matter physics, underlying much of our understanding of conventional materials in terms of defects and geometric frustration in ordered media, and protected edge states in topological insulators. In this talk, I will argue that such an approach successfully identifies the relevant physics in metamaterials and living matter as well, even when traditional techniques fail. The first will be the problem of kirigami mechanics, i.e., designing a pattern of holes in a thin elastic sheet to engineer a specific mechanical response. Using an electrostatic analogy, holes are shown to act as sources of geometric incompatibility, a feature that can fruitfully guide design principles for kirigami metamaterials. In the second half of the talk, I will switch to describe active matter. These are nonequilibrium systems composed of self-driven interacting units that exhibit large scale collective and emergent behaviour, as commonly seen in living systems such as a flock of birds or a bacterial suspension. By focusing on active liquid crystals in two dimensions, with both polar and nematic orientational order, I will show how broken time-reversal symmetry due to the active drive allows polar flocks on a curved surface to support topologically protected sound modes. In an active nematic, activity instead causes topological disclinations to become spontaneously motile, which can drive defect unbinding and organize novel phases of defect order and chaos. In all three cases, geometric and topological ideas enable the relevant degrees of freedom to be identified, allowing complex phenomena to be treated in a tractable fashion, with novel and surprising consequences along the way.