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Graduate Student Yasaman Homayouni, Department of Physics, University of Connecticut, PhD Dissertation Defense1:00pm
2/26
Graduate Student Yasaman Homayouni, Department of Physics, University of Connecticut, PhD Dissertation Defense
Friday, February 26th, 2021
01:00 PM - 03:00 PM
Storrs Campus Video meeting
Graduate Student Yasaman Homayouni, Department of Physics,
University of Connecticut
Supermassive black holes are among the most exciting and unusual objects in our Universe, as literal rips in space and time. Reliable measurements of mass, the structure, and geometry of infalling material to supermassive black holes are critical to understanding the growth history of black holes and galaxy formation and evolution over cosmic time. Beyond the local Universe, the gold standard for black hole mass and accretion-disk structure is reverberation mapping. I will present a new generation of industrial-scale study of the structure, and geometry of infalling material and black hole mass studies from the Sloan Digital Sky Survey Reverberation Mapping (SDSS-RM) project and Ultraviolet-monitoring using the Hubble Space Telescope. These new measurements have transformed our understanding of supermassive black holes by dramatically expanding the number of quasars with reliable mass and accretion structure in distant Universe. These measurements have also revealed a surprisingly large diversity in accretion structure and the broad-line region size of quasars at the peak of supermassive black hole assembly. My work lays the foundation by developing the framework to reliably measure mass and the structure of accretion using direct disk size measurements from future massive time-domain photometric monitoring studies from SDSS-V and Rubin/LSST.
Webex link: https://uconn-cmr.webex.com/join/jot16106 -
Graduate Student Phillip Price, Department of Physics, University of Connecticut, PhD Dissertation Defense1:00pm
12/9
Graduate Student Phillip Price, Department of Physics, University of Connecticut, PhD Dissertation Defense
Wednesday, December 9th, 2020
01:00 PM - 03:00 PM
Storrs Campus Video meeting
Graduate Student Phillip Price, Department of Physics,
University of Connecticut
We propose a model that combines magneto-association across a Feshbach resonance with STIRAP into a continuous and coherent process to form ultra- cold molecules. This can add to the toolbox of ultracold coherent chemistry and potentially enable the production of more ultracold molecules species. To that end, our proposed method should prove beneficial when the Feshbach molecule state has a very short lifetime, with the additional benefit of working within existing experimental setups. -
Graduate Student Kemal Tezgin, Department of Physics, University of Connecticut, "Theoretical and Phenomenological Studies of the Nucleon Structure in High Energy Reactions ", PhD Dissertation Defense1:00pm
11/18
Graduate Student Kemal Tezgin, Department of Physics, University of Connecticut, "Theoretical and Phenomenological Studies of the Nucleon Structure in High Energy Reactions ", PhD Dissertation Defense
Wednesday, November 18th, 2020
01:00 PM - 03:00 PM
Storrs Campus Video meeting
Graduate Student Kemal Tezgin, Department of Physics,
University of Connecticut
Theoretical and Phenomenological Studies of the Nucleon Structure in High Energy Reactions
The understanding of the internal structure of the proton and other strongly interacting particles is at the forefront of modern nuclear physics research. Generalized Parton Distribution Functions (GPDs) are a powerful tool to advance the understanding of the hadron structure. In addition to the information about the one- dimensional collinear momentum distributions of partons (quarks, anti-quarks, and gluons) known from studies of high energy deep-inelastic reactions, GPDs also carry information on the distribution of partons in the transverse plane, and allow us in this way to access the three-dimensional structure of the nucleon. GPDs can be studied in hard-exclusive reactions and contain also information on the energy-momentum tensor form factors which will allow us to gain insights on quantities like pressure or angular momentum distribution inside the nucleon. The goal of this thesis is to deepen our understanding of the three-dimensional structure of the nucleon. We investigate energy-momentum tensor form factors and densities, and all leading-twist GPDs in the bag model. This quark model provides a consistent theoretical framework to investigate many general concepts that have recently attracted interest, and allows one to study insightful limits like the large-Nc limit, heavy-quark limit, or the non-relativistic limit. Another important aspect of this thesis is the discussion of the monopole and quadrupole contributions to the angular momentum density. Finally, the description of pseudoscalar meson production in exclusive processes in terms of GPDs is discussed in the Goloskokov-Kroll model and implemented in the PARTONS framework, a software development project which will provide direct support for experiments at the Jefferson National Lab and the future Electron-Ion Collider. -
Theoretical and Phenomenological Studies of the Nucleon Structure in High Energy Reactions , Doctoral Dissertation Oral Defense Of Kemal Tezgin1:00pm
11/18
Theoretical and Phenomenological Studies of the Nucleon Structure in High Energy Reactions , Doctoral Dissertation Oral Defense Of Kemal Tezgin
Wednesday, November 18th, 2020
01:00 PM - 02:30 PM
Storrs Campus Zoom
Theoretical and Phenomenological Studies of the Nucleon Structure in High Energy Reactions
In high energy collisions, Parton Distribution Functions (PDFs) are fundamental objects to describe one-dimensional collinear momentum distributions of partons (quarks, anti-quarks, and gluons) inside the nucleon. In addition to PDFs, Generalized Parton Distribution Functions (GPDs) also carry information on the distribution of partons in the transverse plane to its motion and allow us to access the three-dimensional structure of the nucleon. On the other hand, energy-momentum tensor (EMT) densities allow us to access the pressure, shear forces, and angular momentum density inside the nucleon. The goal of this thesis is to deepen our understanding of the three-dimensional structure of the nucleon. We investigate energy-momentum tensor (EMT) form factors and densities, and all leading-twist GPDs in the bag model, formulated in the large-N_c limit. We also evaluate all leading-twist chiral-odd GPDs of the relativistic nucleon in the bag model. The consistency of this quark model allows us to investigate many general concepts that have recently attracted interest, including pressure, shear forces, and angular momentum density. Another important aspect of this thesis is to discuss that the monopole and quadrupole contributions to the angular momentum density can be generated from each other uniquely in a model-independent way. The last chapter is dedicated to the phenomenology of GPDs and the Goloskokov-Kroll model's implementation in the PARTONS framework for pseudoscalar meson production in exclusive processes. -
Graduate Student Benjamin Commeau, Department of Physics, University of Connecticut, "Two Studies on Topological Properties of Organic Superconductors and a new Quantum Dynamical Simulation Algorithm", PhD Dissertation Defense2:00pm
9/25
Graduate Student Benjamin Commeau, Department of Physics, University of Connecticut, "Two Studies on Topological Properties of Organic Superconductors and a new Quantum Dynamical Simulation Algorithm", PhD Dissertation Defense
Friday, September 25th, 2020
02:00 PM - 04:00 PM
Storrs Campus Video meeting
Graduate Student Benjamin Commeau, Department of Physics,
University of Connecticut
Two Studies on Topological Properties of Organic Superconductors and a new Quantum Dynamical Simulation Algorithm
In this thesis I investigate two research topics in topological organic superconductors and one research topic in variational algorithms for quantum computation.
In the first chapter we investigate the structural and electronic properties of the three structural phases alpha, beta and kappa of (BEDT-TTF)2I3, by performing state of the art ab initio calculations in the framework of density functional theory. We furthermore report about the irreducible representations of the corresponding electronic band structures, symmetry of their crystal structure, and discuss the origin of band crossings.
Additionally, we discuss the chemically induced strain in kappa-(BEDT-TTF)2I3 achieved by replacing the iodine layer with other Halogens: Fluorine, Bromine and Chlorine. In the case of kappa-(BEDT-TTF)2F3, we identify topologically protected crossings within the band structure. These crossings are forced to occur due to the non-symmorphic nature of the crystal. In the second chapter, we performed structural optimization and electronic structure calculations in the framework of density functional theory, incorporating, first, the recently developed strongly constrained and appropriately normed semilocal density functional SCAN, and, second, van der Waals corrections to the PBE exchange correlation functional by means of the dDsC dispersion correction method.
In the case of alpha-(BEDT-TTF)2F3 the formation of over-tilted Dirac-type-II nodes within the quasi 2-dimensional Brillouin zone can be found.
For kappa-(BEDT-TTF)2F3, the recently reported topological transition within the electronic band structure cannot be revealed. In the third chapter, we propose a new algorithm called Variational Hamiltonian Diagonalization (VHD), which approximately transforms a given Hamiltonian into a diagonal form that can be easily exponentiated. VHD allows for fast forwarding, and removes Trotterization error and allows simulation of the entire Hilbert space. We prove an operational meaning for the VHD cost function in terms of the average simulation fidelity. Moreover, we prove that the VHD cost function does not exhibit a shallow-depth barren plateau. Our numerical simulations verify that VHD can be used for fast-forwarding dynamics.
Zoom Link: https://harvard.zoom.us/j/92203325795?pwd=T2VoYzNPNkwvZW1GWFlhQk9Ga1lwUT09 -
Graduate Student Saman Bastami, Department of Physics, University of Connecticut, "Studies on Hadron Structure through Transverse-Momentum-Dependent Parton Distribution Functions", PhD Dissertation Defense1:15pm
9/11
Graduate Student Saman Bastami, Department of Physics, University of Connecticut, "Studies on Hadron Structure through Transverse-Momentum-Dependent Parton Distribution Functions", PhD Dissertation Defense
Friday, September 11th, 2020
01:15 PM - 03:15 PM
Storrs Campus Video meeting
Graduate Student Saman Bastami, Department of Physics,
University of Connecticut
Studies on Hadron Structure through Transverse-Momentum-Dependent Parton Distribution Functions
The detailed description of hadrons in terms of quarks and gluons, the fundamental degrees of freedom of Quantum Chromodynamics, is an open problem. Important aspects of hadron structure can be studied in certain deep-inelastic high-energy processes which have revealed important insights about the longitudinal momentum distributions of quarks and gluons inside hadrons. Our knowledge of the three-dimensional structure is still very limited. Transverse momentum dependent parton distribution functions (TMDs) are one of the main tools to study the transverse structure of hadrons through processes such as semi-inclusive deep inelastic scattering SIDIS) or the Drell-Yan process. This dissertation is dedicated to phenomenological and model studies of TMDs.
All spin and azimuthal asymmetries of the lepton-nucleon SIDIS are calculated at leading- and subleading twist exploring the so-called "Wandzura-Wilczek-type" approximation which consists in a systematic neglect quark-gluon correlations. The results are obtained using available phenomenological information on TMDs as well as constraints from state-of-the-art lattice QCD calculations, and compared to the experimental data from HERMES, COMPASS and Jefferson Lab.
The asymmetries of the pion-induced Drell-Yan process with polarized protons are studied at leading twist. The information about TMDs is taken from non-perturbative calculations in the lightfront constituent quark model, the spectator model and, where available, phenomenological extractions of TMDs. The results are compared to recent data from the first polarized pion-nucleon Drell-Yan experiment performed by the COMPASS Collaboration at CERN, and predictions for future experiments are made.
The "covariant parton model", an effective hadronic model based on the intuitive parton model concept, is extended and formalized. This allows one to compute all time-reversal-even TMDs of leading and subleading twist in a systematic way. This model naturally supports the Wandzura-Wilczek-type approximations and predicts several non-trivial relations between TMDs, many of which are supported in other model frameworks and can be tested in experiments. Applications and limitations of the model are discussed.
Meeting video link: https://zoom.us/j/96866754697?pwd=NEM1WUt3VkxhbVdQQWdacVVubHNvQT09 -
Doctoral Dissertation Oral Defense of Saman Bastami1:30pm
9/7
Doctoral Dissertation Oral Defense of Saman Bastami
Monday, September 7th, 2020
01:30 PM - 03:00 PM
Other Zoom
Studies on Hadron Structure through Transverse Momentum Dependent Parton Distribution Functions -
Graduate Student Brandon A. Clary, Department of Physics, University of Connecticut, "Exclusive Phi Production Beam Spin Asymmetry Measurements with CLAS12", PhD Dissertation Defense9:30am
8/21
Graduate Student Brandon A. Clary, Department of Physics, University of Connecticut, "Exclusive Phi Production Beam Spin Asymmetry Measurements with CLAS12", PhD Dissertation Defense
Friday, August 21st, 2020
09:30 AM - 11:30 AM
Storrs Campus Video meeting
Graduate Student Brandon A. Clary, Department of Physics,
University of Connecticut
Exclusive Phi Production Beam Spin Asymmetry Measurements with CLAS12
Measurements of the beam spin asymmetry (BSA) of the exclusive electroproduction of the vector phi(1020) meson through its decay into charged Kaons have been performed. The data set used was based on the RG-A run period from the recently upgraded CEBAF Large Acceptance Spectrometer (CLAS12) in Hall B at Jefferson National Lab (JLab). The run period used a 10.6 GeV longitudinally polarized electron beam and an unpolarized hydrogen target. The available statistics collected allow for detailed studies of the W, -t, xB, and Q2 dependencies of the BSA amplitudes from vector phi meson production. The BSA measurements will shed light on the exchange mechanisms responsible for phi production at JLab energies. In this dissertation, a non-zero BSA is observed, which suggests a possible enhancement of pseudo-scalar exchange mechanism near phi production threshold. Therefore, the non-zero BSA may be a result of the interference of the pseudo-scalar exchange mechanism with a scalar one. Ultimately, information on the dominant exchange mechanism will aid in the development of a Generalized Parton Distribution (GPD) based description of these processes in the context of hard to soft transition.
Webex link: https://uconn-cmr.webex.com/uconn-cmr/j.php?MTID=m0844eee0d13477ad76f35797ae8467db -
Graduate Student Daniel McNeel, Department of Physics, University of Connecticut, "Shape Coexistence in \(^{28}\)Mg: Structure of a Transitional Nucleus", PhD Dissertation Defense1:00pm
6/11
Graduate Student Daniel McNeel, Department of Physics, University of Connecticut, "Shape Coexistence in \(^{28}\)Mg: Structure of a Transitional Nucleus", PhD Dissertation Defense
Thursday, June 11th, 2020
01:00 PM - 03:00 PM
Storrs Campus Video meeting
Graduate Student Daniel McNeel, Department of Physics,
University of Connecticut
Shape Coexistence in \(^{28}\)Mg: Structure of a Transitional Nucleus
The structure of nuclei outside the region of stability is an area of ongoing experimental research. Recent investigations in the region around \(^{32}\)Mg have discovered inversions in the usual ordering of shell model states. From these discoveries, theories of the evolution towards this "island of inversion" predict low-lying deformed intruder states for several nuclei in the region. One such nucleus, which exists in the region of transition between the normal and inverted hierarchies, is \(^{28}\)Mg. In this nucleus the ground state is expected to be mixed, i.e. it is a superposition of nearby \(0^+\) neutron pairing configurations. An excited intruder \(0^+\) state will have a different configuration and shape than surrounding states, a property known as shape coexistence.
Multi-nucleon transfer is known to be sensitive to the static deformation of a nucleus. It is also sensitive to both the amplitude and phase of configuration mixed states, and enhances transfer to those states which are similar to the ground state of the target plus two nucleons in single particle orbitals. This makes it a valuable tool to investigate the properties of \(^{28}\)Mg. The two-neutron adding reaction \(^{26}\)Mg(t,p)\(^{28}\)Mg has been used to study the properties of the ground state and excited \(0^+\) states. This experiment was carried out at Argonne National Laboratory using the HELIcal Orbit Spectrometer (HELIOS). HELIOS was designed to overcome the difficulties of measuring reactions in inverse kinematics. Experiments in inverse kinematics consist of a heavy particle, in this case \(^{26}\)Mg, incident on the light particle (\(^3\)H).
Because multi-nucleon transfers are more complex than single particle transfers, a calculation of the nuclear structure must guide the understanding of which configurations will be strongly populated. Shell model calculations have been used to evaluate the structure related transfer amplitudes, which were used as input into Distorted Wave Born Approximation (DWBA) calculations for the reaction. The results of this analysis are the relative contributions of different configurations to the ground state and excited \(0^+\) states, which provide a stringent test of the theoretical prediction of shape coexistence and intruder states.
Video link: https://uconn-cmr.webex.com/meet/dgm14002 -
Graduate Student Matthew Phelps, Department of Physics, University of Connecticut, "Cosmological Fluctuations in Standard and Conformal Gravity", PhD Dissertation Defense10:00am
6/2
Graduate Student Matthew Phelps, Department of Physics, University of Connecticut, "Cosmological Fluctuations in Standard and Conformal Gravity", PhD Dissertation Defense
Tuesday, June 2nd, 2020
10:00 AM - 12:00 PM
Storrs Campus Video meeting
Graduate Student Matthew Phelps, Department of Physics,
University of Connecticut
Cosmological Fluctuations in Standard and Conformal Gravity
In the theory of cosmological perturbations, extensive methods of simplifying the equations of motion and eliminating non-physical gauge modes are required in order to construct the perturbative solutions. One approach, standard within modern cosmology, is to decompose the metric perturbation into a basis of scalars, vectors, and tensors defined according to their transformation behavior under three-dimensional rotations (the S.V.T. decomposition). By constructing a projector formalism to define the basis components, we show that such a decomposition is intrinsically non-local and necessarily incorporates spatially asymptotic boundary conditions. We continue application of the S.V.T. decomposition and solve the fluctuation equations exactly within standard cosmologies as applied to both Einstein gravity and conformal gravity, finding that in general the various S.V.T. gauge-invariant combinations only decouple at a higher-derivative level. To match the underlying transformation group of General Relativity and thus provide a manifestly covariant formalism, we introduce an alternate scalar, vector, tensor basis with components defined according to general four-dimensional coordinate transformations. In this basis, the fluctuation equations greatly simplify, where one can again decouple them into separate gauge-invariant sectors at the higher-derivative level. In the context of conformal gravity, we use similar constructions to solve the fluctuation equations exactly within any geometry that is conformal to flat and show that in a radiation era Robertson-Walker cosmology, fluctuations grow as \(t^4\).
Video Meeting URL: https://uconn-cmr.webex.com/meet/map14010 -
Graduate Student Lukasz Kuna, Department of Physics, University of Connecticut, "Mesoscale Studies of Nanostructured Multi-Functional Materials", PhD Dissertation Defense10:00am
4/16
Graduate Student Lukasz Kuna, Department of Physics, University of Connecticut, "Mesoscale Studies of Nanostructured Multi-Functional Materials", PhD Dissertation Defense
Thursday, April 16th, 2020
10:00 AM - 12:00 PM
Storrs Campus Video meeting
Graduate Student Lukasz Kuna,
Department of Physics,
University of Connecticut
Mesoscale Studies of Nanostructured Multi-Functional Materials
In this dissertation, multiple studies centered around functional properties of materials for applications in devices and novel technologies are carried out utilizing a mesoscale modeling approach. The studies involve simulating the properties of dielectric nano/microstructures with coupled polar and elastic degrees of freedom and developing a greater understanding of their dependence on the structure size, morphology and applied external conditions. Of particular focus in this work are optical properties of electroactive materials including zero- and one-dimensional structures such as nanoparticles and nanowires, as well as mesoscopic functional properties of larger structures such as polycrystalline ceramics (with submicron grain sizes) and ferroelectric mesa structures. The first two research topics are focused on the band gap properties of 1-D semiconductors and modeling of ferroelectric mesa structures, each study serving as an important tool in progressing the understanding of these materials for functional applications. The final topic, comprising the larger portion of the work, presents a novel approach for studying transmission in nanocrystalline ceramics based upon wave-train theory, that is then utilized to predict light transmission in polycrystalline ceramics. In particular, simulations examining the optical properties modulation under different applied mechanical and electrical boundary conditions predict large changes to transmission, including switching from full transparency to opacity in some instances. The results presented in this dissertation highlight an extraordinary promise of functional nano- and microceramics for a wide range of advanced engineering applications.