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Fano 3-Folds, Reflexive Polytopes And Brane Brick Models, Sebastían Franco, Rak-Kyeong Seong

Publications and Research

Reflexive polytopes in n dimensions have attracted much attention both in mathematics and theoretical physics due to their connection to Fano n-folds and mirror symmetry. This work focuses on the 18 regular reflexive polytopes corresponding to smooth Fano 3-folds. For the first time, we show that all 18 regular reflexive polytopes have corresponding 2d (0, 2) gauge theories realized by brane brick models. These 2d gauge theories can be considered as the worldvolume theories of D1-branes probing the toric Calabi-Yau 4-singularities whose toric diagrams are given by the associated regular reflexive polytopes. The generators of the mesonic moduli …

Strain‑Induced Quantum Hall Phenomena Of Excitons In Graphene, Oleg L. Berman, Roman Ya. Kezerashvili, Yurii E. Lozovik, Klaus G. Ziegler

Publications and Research

We study direct and indirect pseudomagnetoexcitons, formed by an electron and a hole in the layers of gapped graphene under strain‑induced gauge pseudomagnetic field. Since the train‑induced pseudomagnetic field acts on electrons and holes the same way, it occurs that the properties of single pseudomagnetoexcitons, their collective effects and phase diagram are cardinally different from those of magnetoexcitons in a real magnetic field. We have derived wave functions and energy spectrum of direct in a monolayer and indirect pseudomagnetoexcitons in a double layer of gapped graphene. The quantum Hall effect for direct and indirect excitons was predicted in the monolayers …

Perspectives On Determinism In Quantum Mechanics: Born, Bohm, And The 'Quantal Newtonian' Laws, Viraht Sahni

Publications and Research

Quantum mechanics has a deterministic Schrödinger equation for the wave function. The Göttingen-Copenhagen statistical interpretation is based on the Born Rule that interprets the wave function as a ‘probability amplitude’. A precept of this interpretation is the lack of determinism in quantum mechanics. The Bohm interpretation is that the wave function is a source of a field experienced by the electrons, thereby attributing determinism to quantum theory. In this paper we present a new perspective on such determinism. The ideas are based on the equations of motion or ‘Quantal Newtonian’ Laws obeyed by each electron. These Laws, derived from the …

A Surrogate Model Of Molecular Dynamics Simulations For Polar Fluids: Supervised Learning Methods For Molecular Polarization And Unsupervised Methods For Phase Classification, Zackerie W. Hjorth

Dissertations, Master's Theses and Master's Reports

Molecular Dynamic (MD) simulation is a standard computational tool in soft matter physics. While very powerful, it is computationally expensive, leading to some simulations taking days or even weeks to complete depending on the size of your computer cluster. Finding computationally cheap surrogate models which can learn the output features of MD simulation is therefore highly motivated. In this report I explore the use of deep neural network ensembles as well as support vector machine regressors as surrogate models for MD simulation. From the output of the surrogate models, we can then employ unsupervised learning methods to get insight into …

The Effects Of "Sticky Stuff" On The Spin Rate And Break Of A Baseball Pitch, Natalie Dale

Scripps Senior Theses

In June 2021, Major League Baseball cracked down on the use of foreign substances by pitchers on the ball (Castrovince, 2021a). It is believed the sticky substances give the pitchers an unfair advantage over batters since they increase spin rate, consequently, through the Magnus Effect, creating more movement or “break” in the pitch, making it harder to hit. There are existing gaps in empirical research on this topic, thus the goal of this project was to determine the effect the banned substances have on the spin rate and related break of the pitches. By using pitch tracking technology, two types …

Using Powder Diffraction To Give Insight Into Structures Of Ir2(Diisocyanomenthane)4x2 [Dimen] (X = Cl; Pf6; Bph4), Mairead Brownell

Scripps Senior Theses

Ir2(dimen)42+ (dimen = 1,8-diisocyanomenthane) has been studied extensively as model compound to better understand catalysis of photochemical reactions. Although Ir2(dimen)42+ has been used primarily to observe the photophysical changes of metal-metal transitions, it gives great insight into the transitions that allow other d8-d8 metal complexes to undergo photochemical processes and generate hydrogen gas. The large visible range by which Ir2(dimen)42+ (1) can be electronically excited in solution is indicative of its two solution phase ground states, which interestingly have been hypothesized to resemble two unique packing structures observed in the powder state. In this study, the powder diffraction patterns of …

Characterization Of Undoped Csi At Cryogenic Temperatures, Yongjin Yang

Dissertations and Theses

Doped CSI (Cesium iodide) is wildly used in many detectors. Pure cesium iodide can only perform well at low temperature due to its luminous properties. Its luminous efficiency at low temperature is even better than that of impurity-containing cesium iodide. So we want to measure its properties at low temperatures. In chapter 3, we measure the light yield of the pure CSI, which is the important property as a detector. We also introduce our experimental equipment and methods. In chapter 4, the quenching factor represents the efficiency of energy deposition. This value is a key point for our future detection …

Magnetic And Mechanical Properties Of Ultrasoft Magnetorheological Elastomers, Andy T. Clark

Bryn Mawr College Dissertations and Theses

Magnetorheological elastomers (MREs), composite materials consisting of magnetic particles embedded in a non-magnetic elastomeric matrix, can reversibly modulate their mechanical and magnetic properties through tuning the applied magnetic field H. Recently, ultrasoft MREs have received tremendous attention due to their great potential in biomedical applications. However, the effects of the polymer stiffness and magnetic particle concentration on the magnetic and mechanical properties of ultrasoft MREs still need to be better understood. In this dissertation, the author presents a comprehensive investigation of the magnetic and mechanical properties of ultrasoft MREs as well as their biomedical applications.

The effect of polymer …

Characterizing Agn Influence On The Calculated Metallicities Of Adjacent Star-Forming Spaxels, Aidan Khelil

Honors Papers

In this thesis, I introduce a method to identify and characterize the effects of active galactic nuclei (AGN) on the spectra of nearby star-forming regions. I analyze spatially-resolved areas of galaxies called “spaxels” within Data Release 15 of the Sloan Digital Sky Survey (SDSS) with the goal of locating those which are physically close to AGN. I find those spaxels with calculated metallicities which lie adjacent to AGN-flagged spaxels and characterize their metallicity values relative to the spaxels which are not adjacent to AGN-flagged spaxels, using a total of 11 separate metallicity calibrations. I find that the current methods to …

Meltpondnet: A Swin Transformer U-Net For Detection Of Melt Ponds On Arctic Sea Ice, Ivan Sudakow, Vijayan K. Asari, Ruixu Liu, Denis Demchev

Electrical and Computer Engineering Faculty Publications

High-resolution aerial photographs of Arctic region are a great source for different sea ice feature recognition, which are crucial to validate, tune, and improve climate models. Melt ponds on the surface of melting Arctic sea ice are of particular interest as they are sensitive and valuable indicators and are proxy to the processes in the Arctic climate system. Manual analysis of this remote sensing data is extremely difficult and time-consuming due to the complex shapes and unpredictable boundaries of the melt ponds, and that leads to the necessity for automatizing the processes. In this study, we propose a robust and …

Circuit Optimization Techniques For Efficient Ex-Situ Training Of Robust Memristor Based Liquid State Machine, Alex Henderson, Christopher Yakopcic, Cory Merkel, Steven Harbour, Tarek M. Taha, Hananel Hazan

Electrical and Computer Engineering Faculty Publications

Spiking neural network hardware offers a high performance, power-efficient and robust platform for the processing of complex data. Many of these systems require supervised learning, which poses a challenge when using gradient-based algorithms due to the discontinuous properties of SNNs. Memristor based hardware can offer gains in portability, power reduction, and throughput efficiency when compared to pure CMOS. This paper proposes a memristor-based spiking liquid state machine (LSM). The inherent dynamics of the LSM permit the use of supervised learning without backpropagation for weight updates. To carry out the design space evaluation of the LSM for optimal hardware performance, several …

Observation Of Localized Magnetic Plasmon Skyrmions, Zi-Lan Deng, Tan Shi, Alex Krasnok, Xiangping Li, Andrea Alù

Advanced Science Research Center

Optical skyrmions have recently been constructed by tailoring vectorial near-field distributions through the interference of multiple surface plasmon polaritons, offering promising features for advanced information processing, transport and storage. Here, we provide experimental demonstration of electromagnetic skyrmions based on magnetic localized spoof plasmons (LSP) showing large topological robustness against continuous deformations, without stringent external interference conditions. By directly measuring the spatial profile of all three vectorial magnetic fields, we reveal multiple ��-twist target skyrmion configurations mapped to multi-resonant near-equidistant LSP eigenmodes. The real-space skyrmion topology is robust against deformations of the meta-structure, demonstrating flexible skyrmionic textures for arbitrary shapes. The …

Bias Impedes Progress In Physical Biology, Consciousness Studies And Quantum Gravity, Maurice Goodman

Articles

If scientists hope to make progress in consciousness studies they needs to accept that biased judgments have a major influence on the sciences, how we divide them up, how they are funded and this, in turn, has a profound impact on progress. The imbalance in funding, resulting from bias, in favour of the life and health sciences needs to be addressed as does why perversely little of this funding is devoted to a physics explanation of self-organisation and life on the mesoscopic scale? While life (the cell) is an outstanding example of self-organisation on the mesoscopic scale we need to …

Theoretical Investigation On Optical Properties Of 2d Materials And Mechanical Properties Of Polymer Composites At Molecular Level, Geeta Sachdeva

Dissertations, Master's Theses and Master's Reports

The field of two-dimensional (2D) layered materials provides a new platform for studying diverse physical phenomena that are scientifically interesting and relevant for technological applications. Theoretical predictions from atomically resolved computational simulations of 2D materials play a pivotal role in designing and advancing these developments. The focus of this thesis is 2D materials especially graphene and BN studied using density functional theory (DFT) and molecular dynamics (MD) simulations. In the first half of the thesis, the electronic structure and optical properties are discussed for graphene, antimonene, and borophene. It is found that the absorbance in (atomically flat) multilayer antimonene (group …

Persistence Of Height Fluctuation In Molecular-Beam Epitaxy Model, Pipitton Sanseeha

Chulalongkorn University Theses and Dissertations (Chula ETD)

Persistence probability is an interesting quantity in stochastic process which is the dynamics of surface growth in this study. Persistence probability of height f luctuation is the probability that the height fluctuation does not return to its initial value throughout a time interval. In this work, we use a numerical simulation approach to investigate the persistence probability in Molecular-Beam Epitaxy (MBE) model which is associated with Molecular-Beam Epitaxy technique. First half, we study the effects of temperature and deposition rate on the growth exponent () and persistence exponent (). For the temperature corresponds to 1 diffusion length, we get 017 …

Random Walks On Quasi-1d Infinite Structures, Srawut Sasom

Chulalongkorn University Theses and Dissertations (Chula ETD)

In the present thesis a random walk on quasi-1d lattices as a model for transport processes on quasi-1d materials is analytically investigated. The scope of the present work is to shed light on the asymptotic behavior of basic statistical properties of the random walk on such structures including the first and the second moments of the walker location along the structure axis, the probability of return to the starting site, the probability of ever reach a given site, the conditional mean first-passage time to a given site and the expected number of distinct sites visited. The first part of the …

From Evaluating The Performance Of Approximations In Density Functional Theory To A Machine Learning Design, Pedram Tavazohi

Graduate Theses, Dissertations, and Problem Reports (ETD)

Density-functional theory (DFT) has gained popularity because of its ability to predict the properties of a large group of materials a priori. Even though DFT is exact, there are inaccuracies introduced into the theory due to the approximations in the exchange-correlation (XC) functionals. Over the 50 years of its existence, scientists have tried to improve the design of the XC functionals. The errors introduced by these functionals are not consistent across all types of solid-state materials. In this project, a high throughput framework was utilized to compare the theoretical DFT predictions with the experimental results available in the Inorganic Crystal …

Charge Dynamics Of Inas Quantum Dots Under Resonant And Above-Band Excitation, Gary R. Lander Jr

Graduate Theses, Dissertations, and Problem Reports (ETD)

Research involving light-matter interactions in semiconductor nanostructures has been an interesting topic of investigation for decades. Many systems have been studied for not only probing fundamental physics of the solid state, but also for direct development of technological advancements. Research regarding self-assembled, epitaxially grown quantum dots (QDs) has proven to be prominent in both regards. The development of a reliable, robust source for the production of quantum bits to be utilized in quantum information protocols is a leading venture in the world of condensed matter and solid-state physics. Fluorescence from resonantly driven QDs is a promising candidate for the production …

Microwave Enhanced Electron Energy Distribution Functions, John Samuel Mckee

Graduate Theses, Dissertations, and Problem Reports (ETD)

The use of two (or more) radio frequency (RF) sources at different frequencies is a common technique in the plasma processing industry to control ion energy characteristics separately from plasma generation. A similar approach is presented here with the focus on modifying the electron population in argon and helium plasmas. The plasma is generated by a helicon source at a frequency f0 = 13.56 MHz. Microwaves of frequency f1 = 2.45 GHz are then injected into the helicon source chamber perpendicular to the background magnetic field. The microwaves damp on the electrons via R-mode (anti-parallel to the background magnetic field …

Scaling Theory Of 3d Magnetic Reconnection X-Line Spreading, Milton Arencibia

Graduate Theses, Dissertations, and Problem Reports (ETD)

Magnetic reconnection is fundamental process in plasmas that converts magnetic energy into kinetic and thermal energy via a change in magnetic topology. Magnetic reconnection is known to mediate eruptive solar flares, geomagnetic substorms that create the Northern lights, heating and particle acceleration in controlled fusion devices, and is thought to be an important process in numerous settings in high-energy astrophysics. Classical models of reconnection are two-dimensional (2D), but naturally occurring reconnection is three-dimensional (3D), and a manifestation of the 3D nature is that the x-line where the magnetic field topology changes has a finite extent in the direction normal to …

Planar Chiral Metasurfaces With Maximal And Tunable Chiroptical Response Driven By Bound States In The Continuum, Tan Shi, Zi-Lan Deng, Guangzhou Geng, Xianzhi Zeng, Yixuan Zeng, Guangwei Hu, Adam Overvig, Junjie Li, Cheng-Wei Qiu, Andrea Alù, Yuri S. Kivshar, Xiangping Li

Advanced Science Research Center

Optical metasurfaces with high quality factors (Q-factors) of chiral resonances can boost substantially light-matter interaction for various applications of chiral response in ultrathin, active, and nonlinear metadevices. However, current approaches lack the flexibility to enhance and tune the chirality and Q-factor simultaneously. Here, we suggest a design of chiral metasurface supporting bound state in the continuum (BIC) and demonstrate experimentally chiroptical responses with ultra-high Q-factors and near-perfect circular dichroism (CD = 0.93) at optical frequencies. We employ the symmetry-reduced metaatoms with high birefringence supporting winding elliptical eigenstate polarizations with opposite helicity. It provides a convenient way for achieving the maximal …

Reciprocity Of Thermal Diffusion In Time-Modulated Systems, Jiaxin Li, Ying Li, Pei-Chao Cao, Minghong Qi, Xu Zheng, Yu-Gui Peng, Baowen Li, Xue-Feng Zhu, Andrea Alù, Hongsheng Chen, Cheng-Wei Qiu

Advanced Science Research Center

The reciprocity principle governs the symmetry in transmission of electromagnetic and acoustic waves, as well as the diffusion of heat between two points in space, with important consequences for thermal management and energy harvesting. There has been significant recent interest in materials with time-modulated properties, which have been shown to efficiently break reciprocity for light, sound, and even charge diffusion. However, time modulation may not be a plausible approach to break thermal reciprocity, in contrast to the usual perception. We establish a theoretical framework to accurately describe the behavior of diffusive processes under time modulation, and prove that thermal reciprocity …

Coherent Full Polarization Control Based On Bound States In The Continuum, Ming Kang, Ziying Zhang, Tong Wu, Xueqian Zhang, Quan Xu, Alex Krasnok, Jiaguang Han, Andrea Alù

Advanced Science Research Center

Bound states in the continuum (BICs) are resonant modes of open structures that do not suffer damping, despite being compatible with radiation in terms of their momentum. They have been raising significant attention for their intriguing topological features, and their opportunities in photonics to enhance light-matter interactions. In parallel, the coherent excitation of optical devices through the tailored interference of multiple beams has been explored as a way to enhance the degree of real-time control over their response. Here, we leverage the combination of these phenomena, and exploit the topological features of BICs in the presence of multiple input beams …

Fast Encirclement Of An Exceptional Point For Highly Efficient And Compact Chiral Mode Converters, Xiaoqian Shu, Aodong Li, Guangwei Hu, Jian Wang, Andrea Alù, Lin Chen

Advanced Science Research Center

Exceptional points (EPs) are degeneracies at which two or more eigenvalues and eigenstates of a physical system coalesce. Dynamically encircling EPs by varying the parameters of a non- Hermitian system enables chiral mode switching, that is, the final state of the system upon a closed loop in parameter space depends on the encircling handedness. In conventional schemes, the parametric evolution during the encircling process has to be sufficiently slow to ensure adiabaticity. Here, we show that fast parametric evolution along the parameter space boundary of the system Hamiltonian can relax this constraint. The proposed scheme enables highly efficient transmission and …

Stability Bounds On Superluminal Propagation In Active Structures, Robert Duggan, Hady Moussa, Younes Ra'di, Dimitrios L. Sounas, Andrea Alù

Advanced Science Research Center

Active materials have been explored in recent years to demonstrate superluminal group velocities over relatively broad bandwidths, implying a potential path towards bold claims such as information transport beyond the speed of light, as well as antennas and metamaterial cloaks operating over very broad bandwidths. However, causality requires that no portion of an impinging pulse can pass its precursor, implying a fundamental trade-off between bandwidth, velocity and propagation distance. Here, we clarify the general nature of superluminal propagation in active structures and derive a bound on these quantities fundamentally rooted into stability considerations. By applying filter theory, we show that …

Radio-Transparent Dipole Antenna Based On A Metasurface Cloak, Jason Soric, Younes Ra'di, Diego Farfan, Andrea Alù

Advanced Science Research Center

Antenna technology is at the basis of ubiquitous wireless communication systems and sensors. Radiation is typically sustained by conduction currents flowing around resonant metallic objects that are optimized to enhance efficiency and bandwidth. However, resonant conductors are prone to large scattering of impinging waves, leading to challenges in crowded antenna environments due to blockage and distortion. Metasurface cloaks have been explored in the quest of addressing this challenge by reducing antenna scattering. However, metasurface-based designs have so far shown limited performance in terms of bandwidth, footprint and overall scattering reduction. Here we introduce a different route towards radiotransparent antennas, in …

Moiré-Driven Topological Transitions And Extremeanisotropy In Elastic Metasurfaces, Simon Yves, Matheus Inguaggiato Nora Nora Rosa, Mohit Gupta, Massimo Ruzzene, Andrea Alù

Advanced Science Research Center

The twist angle between a pair of stacked 2D materials has been recently shown to control remarkable phenomena, including the emergence of flat-band superconductivity in twisted graphene bilayers, of higher-order topological phases in twisted moiré superlattices, and of topological polaritons in twisted hyperbolic metasurfaces. These discoveries, at the foundations of the emergent field of twistronics, have so far been mostly limited to explorations in atomically thin condensed matter and photonic systems, with limitations on the degree of control over geometry and twist angle, and inherent challenges in the fabrication of carefully engineered stacked multilayers. Here, this work extends twistronics to …

Photonics Of Time-Varying Media, Emanuele Galiffi, Romain Tirole, Shixiong Yin, Huanan Li, Stefano Vezzoli, Paloma A. Huidobro, Mário G. Silveirinha, Riccardo Sapienza, Andrea Alù, J. B. Pendry

Advanced Science Research Center

Time-varying media have recently emerged as a new paradigm for wave manipulation, due to the synergy between the discovery of highly nonlinear materials, such as epsilon-near-zero materials, and the quest for wave applications, such as magnet-free nonreciprocity, multimode light shaping, and ultrafast switching. In this review, we provide a comprehensive discussion of the recent progress achieved with photonic metamaterials whose properties stem from their modulation in time. We review the basic concepts underpinning temporal switching and its relation with spatial scattering and deploy the resulting insight to review photonic time-crystals and their emergent research avenues, such as topological and non-Hermitian …

Short-Distance Structure Of Unpolarized Gluon Pseudodistributions, Ian Balitsky, Wayne Morris, Anatoly Radyushkin

Physics Faculty Publications

We present the results that form the basis for calculations of the unpolarized gluon parton distributions (PDFs) using the pseudo-PDF approach. We give the results for the most complicated box diagram both for gluon bilocal operators with arbitrary indices and for combinations of indices corresponding to three matrix elements that are most convenient to extract the twist-2 invariant amplitude. We also present detailed results for the gluon-quark transition diagram. The additional results for the box diagram and the gluon-quark contribution may be used for extractions of the gluon PDF from different matrix elements, with a possible cross-check of the results …

Neutrino Energy Reconstruction From Semi-Inclusive Samples, R. González-Jiménez, M. B. Barbaro, J. A. Caballero, T. W. Donnelly, N. Jachowicz, G.D. Megias, K. Niewczas, A. Nikolakopoulos, J.W. Van Orden, J. M. Udías

Physics Faculty Publications

We study neutrino-nucleus charged-current reactions on finite nuclei for the situation in which an outgoing muon and a proton are detected in coincidence; i.e., we focus on semi-inclusive cross sections. We limit our attention to one-body current interactions (quasielastic scattering) and assess the impact of different nuclear effects in the determination of the neutrino energy. We identify the regions in phase space where the neutrino energy can be reconstructed relatively well and study whether the cross section in those regions is significant. Our results indicate that it is possible to filter more than 50% of all events according to the …