Matching Items (20)
Description
An X class solar flare has the potential to remove our satellites from orbit, permanently deactivate our main forms of communication and bring humanity into a technology-free age. By using Geant4, it is possible to simulate several layers of the Earth's atmosphere and send a simulated solar flare and coronal mass ejection. This thesis will show the interaction of photons and protons of various energies with several kilometers of atmosphere.
ContributorsDolghier, Kristian Adrian (Author) / Shovkovy, Igor (Thesis director) / Steinkamp, Brian (Committee member) / Economics Program in CLAS (Contributor) / College of Integrative Sciences and Arts (Contributor, Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
Description
The nucleon resonance spectrum consists of many overlapping excitations. Polarization observables are an important tool for understanding and clarifying these spectra. While there is a large data base of differential cross sections for the process, very few data exist for polarization observables. A program of double polarization experiments has been conducted at Jefferson Lab using a tagged polarized photon beam and a frozen spin polarized target (FROST). The results presented here were taken during the first running period of FROST using the CLAS detector at Jefferson Lab with photon energies ranging from 329 MeV to 2.35 GeV. Data are presented for the E polarization observable for eta meson photoproduction on the proton from threshold (W=1500 MeV) to W=1900 MeV. Comparisons to the partial wave analyses of SAID and Bonn-Gatchina along with the isobar analysis of eta-MAID are made. These results will help distinguish between current theoretical predictions and refine future theories.
ContributorsMorrison, Brian (Author) / Ritchie, Barry (Thesis advisor) / Dugger, Michael (Committee member) / Shovkovy, Igor (Committee member) / Davies, Paul (Committee member) / Alarcon, Ricardo (Committee member) / Arizona State University (Publisher)
Created2011
Description
Monte Carlo methods often used in nuclear physics, such as auxiliary field diffusion Monte Carlo and Green's function Monte Carlo, have typically relied on phenomenological local real-space potentials containing as few derivatives as possible, such as the Argonne-Urbana family of interactions, to make sampling simple and efficient. Basis set methods such as no-core shell model or coupled-cluster techniques typically use softer non-local potentials because of their more rapid convergence with basis set size. These non-local potentials are typically defined in momentum space and are often based on effective field theory. Comparisons of the results of the two types of methods are complicated by the use of different potentials. This thesis discusses progress made in using such non-local potentials in quantum Monte Carlo calculations of light nuclei. In particular, it shows methods for evaluating the real-space, imaginary-time propagators needed to perform quantum Monte Carlo calculations using non-local potentials and universality properties of these propagators, how to formulate a good trial wave function for non-local potentials, and how to perform a "one-step" Green's function Monte Carlo calculation for non-local potentials.
ContributorsLynn, Joel E (Author) / Schmidt, Kevin E (Thesis advisor) / Alarcon, Ricardo (Committee member) / Lebed, Richard (Committee member) / Shovkovy, Igor (Committee member) / Shumway, John (Committee member) / Arizona State University (Publisher)
Created2013
Description
In this thesis, we present the study of several physical properties of relativistic mat- ters under extreme conditions. We start by deriving the rate of the nonleptonic weak processes and the bulk viscosity in several spin-one color superconducting phases of quark matter. We also calculate the bulk viscosity in the nonlinear and anharmonic regime in the normal phase of strange quark matter. We point out several qualitative effects due to the anharmonicity, although quantitatively they appear to be relatively small. In the corresponding study, we take into account the interplay between the non- leptonic and semileptonic weak processes. The results can be important in order to relate accessible observables of compact stars to their internal composition. We also use quantum field theoretical methods to study the transport properties in monolayer graphene in a strong magnetic field. The corresponding quasi-relativistic system re- veals an anomalous quantum Hall effect, whose features are directly connected with the spontaneous flavor symmetry breaking. We study the microscopic origin of Fara- day rotation and magneto-optical transmission in graphene and show that their main features are in agreement with the experimental data.
ContributorsWang, Xinyang, Ph.D (Author) / Shovkovy, Igor (Thesis advisor) / Belitsky, Andrei (Committee member) / Easson, Damien (Committee member) / Peng, Xihong (Committee member) / Vachaspati, Tanmay (Committee member) / Arizona State University (Publisher)
Created2013
Description
This thesis addresses certain quantum aspects of the event horizon using the AdS/CFT correspondence. This correspondence is profound since it describes a quantum theory of gravity in d + 1 dimensions from the perspective of a dual quantum field theory living in d dimensions. We begin by considering Rindler space which is the part of Minkowski space seen by an observer with a constant proper acceleration. Because it has an event horizon, Rindler space has been studied in great detail within the context of quantum field theory. However, a quantum gravitational treatment of Rindler space is handicapped by the fact that quantum gravity in flat space is poorly understood. By contrast, quantum gravity in anti-de Sitter space (AdS), is relatively well understood via the AdS/CFT correspondence. Taking this cue, we construct Rindler coordinates for AdS (Rindler-AdS space) in d + 1 spacetime dimensions. In three spacetime dimensions, we find novel one-parameter families of stationary vacua labeled by a rotation parameter β. The interesting thing about these rotating Rindler-AdS spaces is that they possess an observer-dependent ergoregion in addition to having an event horizon. Turning next to the application of AdS/CFT correspondence to Rindler-AdS space, we posit that the two Rindler wedges in AdSd+1 are dual to an entangled conformal field theory (CFT) that lives on two boundaries with geometry R × Hd-1. Specializing to three spacetime dimensions, we derive the thermodynamics of Rindler-AdS space using the boundary CFT. We then probe the causal structure of the spacetime by sending in a time-like source and observe that the CFT “knows” when the source has fallen past the Rindler horizon. We conclude by proposing an alternate foliation of Rindler-AdS which is dual to a CFT living in de Sitter space. Towards the end, we consider the concept of weak measurements in quantum mechanics, wherein the measuring instrument is weakly coupled to the system being measured. We consider such measurements in the context of two examples, viz. the decay of an excited atom, and the tunneling of a particle trapped in a well, and discuss the salient features of such measurements.
ContributorsSamantray, Prasant (Author) / Parikh, Maulik (Thesis advisor) / Davies, Paul (Committee member) / Vachaspati, Tanmay (Committee member) / Easson, Damien (Committee member) / Alarcon, Ricardo (Committee member) / Arizona State University (Publisher)
Created2012
Description
For this project, the diffuse supernova neutrino background (DSNB) has been calculated based on the recent direct supernova rate measurements and neutrino spectrum from SN1987A. The estimated diffuse electron antineutrino flux is ∼ 0.10 – 0.59 /cm2/s at 99% confidence level, which is 5 times lower than the Super-Kamiokande 2012 upper limit of 3.0 /cm2/s, above energy threshold of 17.3 MeV. With a Megaton scale water detector, 40 events could be detected above the threshold per year. In addition, the detectability of neutrino bursts from direct black hole forming collapses (failed supernovae) at Megaton detectors is calculated. These neutrino bursts are energetic and with short time duration, ∼ 1s. They could be identified by the time coincidence of N ≥2 or N ≥3 events within 1s time window from nearby (4 – 5 Mpc) failed supernovae. The detection rate of these neutrino bursts could get up to one per decade. This is a realistic way to detect a failed supernova and gives a promising method for studying the physics of direct black hole formation mechanism. Finally, the absorption of ultra high energy (UHE) neutrinos by the cosmic neutrino background, with full inclusion of the effect of the thermal distribution of the background on the resonant annihilation channel, is discussed. Results are applied to serval models of UHE neutrino sources. Suppression effects are strong for sources that extend beyond z ∼ 10. This provides a fascinating probe of the physics of the relic neutrino background in the unexplored redshift interval z ∼ 10 – 100. Ultimately this research will examine the detectability of DSNB, neutrino bursts from failed supernovae and absorption effects in the neutrino spectrum.
ContributorsYang, Lili, 1970- (Author) / Lunardini, Cecilia (Thesis advisor) / Alarcon, Ricardo (Committee member) / Shovkovy, Igor (Committee member) / Timmes, Francis (Committee member) / Vachaspati, Tanmay (Committee member) / Arizona State University (Publisher)
Created2013
Description
Much attention has been given to the behavior of quantum fields in expanding Freidmann-Lema\^itre-Robertson-Walker (FLRW) spacetimes, and de Sitter spacetime in particular. In such spacetimes, the S-matrix is ill-defined, so new observables must be constructed that are accessible to both computation and measurement. The most common observable in theories of inflation is an equal-time correlation function, typically computed in the in-in formalism. Weinberg improved upon in-in perturbation theory by reducing the perturbative expansion to a series of nested commutators. Several authors noted a technical difference between Weinberg's formula and standard in-in perturbation theory. In this work, a proof of the order-by-order equivalence of Weinberg's commutators to traditional in-in perturbation theory is presented for all masses and commonly studied spins in a broad class of FLRW spacetimes. Then, a study of the effects of a sector of conformal matter coupled solely to gravity is given. The results can constrain N-naturalness as a complete solution of the hierarchy problem, given a measurement of the tensor fluctuations from inflation. The next part of this work focuses on the thermodynamics of de Sitter. It has been known for decades that there is a temperature associated with a cosmological horizon, which matches the thermal response of a comoving particle detector in de Sitter. A model of a perfectly reflecting cavity is constructed with fixed physical size in two-dimensional de Sitter spacetime. The natural ground state inside the box yields no response from a comoving particle detector, implying that the box screens out the thermal effects of the de Sitter horizon. The total energy inside the box is also shown to be smaller than an equivalent volume of the Bunch-Davies vacuum state. The temperature difference across the wall of the box might drive a heat engine, so an analytical model of the Szil\'ard engine is constructed and studied. It is found that all relevant thermodynamical quantities can be computed exactly at all stages of the engine cycle.
ContributorsThomas, Logan (Author) / Baumgart, Matthew (Thesis advisor) / Davies, Paul (Committee member) / Easson, Damien (Committee member) / Keeler, Cynthia (Committee member) / Arizona State University (Publisher)
Created2023
Description
Measurements of the response of superconducting nanowire single photon detector (SNSPD) devices to changes in various forms of input power can be used for characterization of the devices and for probing device-level physics. Two niobium nitride (NbN) superconducting nanowires developed for use as SNSPD devices are embedded as the inductive (L) component in resonant inductor/capacitor (LC) circuits coupled to a microwave transmission line. The capacitors are low loss commercial chip capacitors which limit the internal quality factor of the resonators to approximately $Qi = 170$. The resonator quality factor, approximately $Qr = 23$, is dominated by the coupling to the feedline and limits the detection bandwidth to on the order of 1MHz. In our experiments with this first generation device, we measure the response of the SNSPD devices to changes in thermal and optical power in both the time domain and the frequency domain. Additionally, we explore the non-linear response of the devices to an applied bias current. For these nanowires, we find that the band-gap energy is $\Delta_0 \approx 1.1$meV and that the density of states at the Fermi energy is $N_0 \sim 10^{10}$/eV/$\mu$m$^3$.
We present the results of experimentation with a superconducting nanowire that can be operated in two detection modes: i) as a kinetic inductance detector (KID) or ii) as a single photon detector (SPD). When operated as a KID mode in linear mode, the detectors are AC-biased with tones at their resonant frequencies of 45.85 and 91.81MHz. When operated as an SPD in Geiger mode, the resonators are DC biased through cryogenic bias tees and each photon produces a sharp voltage step followed by a ringdown signal at the resonant frequency of the detector. We show that a high AC bias in KID mode is inferior for photon counting experiments compared to operation in a DC-biased SPD mode due to the small fraction of time spent near the critical current with an AC bias. We find a photon count rate of $\Gamma_{KID} = 150~$photons/s/mA in a critically biased KID mode and a photon count rate of $\Gamma_{SPD} = 10^6~$photons/s/mA in SPD mode.
This dissertation additionally presents simulations of a DC-biased, frequency-multiplexed readout of SNSPD devices in Advanced Design System (ADS), LTspice, and Sonnet. A multiplexing factor of 100 is achievable with a total count rate of $>5$MHz. This readout could enable a 10000-pixel array for astronomy or quantum communications. Finally, we present a prototype array design based on lumped element components. An early implementation of the array is presented with 16 pixels in the frequency range of 74.9 to 161MHz. We find good agreement between simulation and experimental data in both the time domain and the frequency domain and present modifications for future versions of the array.
We present the results of experimentation with a superconducting nanowire that can be operated in two detection modes: i) as a kinetic inductance detector (KID) or ii) as a single photon detector (SPD). When operated as a KID mode in linear mode, the detectors are AC-biased with tones at their resonant frequencies of 45.85 and 91.81MHz. When operated as an SPD in Geiger mode, the resonators are DC biased through cryogenic bias tees and each photon produces a sharp voltage step followed by a ringdown signal at the resonant frequency of the detector. We show that a high AC bias in KID mode is inferior for photon counting experiments compared to operation in a DC-biased SPD mode due to the small fraction of time spent near the critical current with an AC bias. We find a photon count rate of $\Gamma_{KID} = 150~$photons/s/mA in a critically biased KID mode and a photon count rate of $\Gamma_{SPD} = 10^6~$photons/s/mA in SPD mode.
This dissertation additionally presents simulations of a DC-biased, frequency-multiplexed readout of SNSPD devices in Advanced Design System (ADS), LTspice, and Sonnet. A multiplexing factor of 100 is achievable with a total count rate of $>5$MHz. This readout could enable a 10000-pixel array for astronomy or quantum communications. Finally, we present a prototype array design based on lumped element components. An early implementation of the array is presented with 16 pixels in the frequency range of 74.9 to 161MHz. We find good agreement between simulation and experimental data in both the time domain and the frequency domain and present modifications for future versions of the array.
ContributorsSchroeder, Edward, Ph.D (Author) / Mauskopf, Philip (Thesis advisor) / Chamberlin, Ralph (Committee member) / Lindsay, Stuart (Committee member) / Newman, Nathan (Committee member) / Easson, Damien (Committee member) / Arizona State University (Publisher)
Created2018
Description
Chiral symmetry and its anomalous and spontaneous breaking play an important role
in particle physics, where it explains the origin of pion and hadron mass hierarchy
among other things.
Despite its microscopic origin chirality may also lead to observable effects
in macroscopic physical systems -- relativistic plasmas made of chiral
(spin-$\frac{1}{2}$) particles.
Such plasmas are called \textit{chiral}.
The effects include non-dissipative currents in external fields that could be present
even in quasi-equilibrium, such as the chiral magnetic (CME) and separation (CSE)
effects, as well as a number of inherently chiral collective modes
called the chiral magnetic (CMW) and vortical (CVW) waves.
Applications of chiral plasmas are truly interdisciplinary, ranging from
hot plasma filling the early Universe, to dense matter in neutron stars,
to electronic band structures in Dirac and Weyl semimetals, to quark-gluon plasma
produced in heavy-ion collisions.
The main focus of this dissertation is a search for traces of chiral physics
in the spectrum of collective modes in chiral plasmas.
I start from relativistic chiral kinetic theory and derive
first- and second-order chiral hydrodynamics.
Then I establish key features of an equilibrium state that describes many
physical chiral systems and use it to find the full spectrum of collective modes
in high-temperature and high-density cases.
Finally, I consider in detail the fate of the two inherently chiral waves, namely
the CMW and the CVW, and determine their detection prospects.
The main results of this dissertation are the formulation of a fully covariant
dissipative chiral hydrodynamics and the calculation of the spectrum of collective
modes in chiral plasmas.
It is found that the dissipative effects and dynamical electromagnetism play
an important role in most cases.
In particular, it is found that both the CMW and the CVW are heavily damped by the usual
Ohmic dissipation in charged plasmas and the diffusion effects in neutral plasmas.
These findings prompt a search for new physical observables in heavy-ion collisions,
as well as a revision of potential applications of chiral theories in
cosmology and solid-state physics.
in particle physics, where it explains the origin of pion and hadron mass hierarchy
among other things.
Despite its microscopic origin chirality may also lead to observable effects
in macroscopic physical systems -- relativistic plasmas made of chiral
(spin-$\frac{1}{2}$) particles.
Such plasmas are called \textit{chiral}.
The effects include non-dissipative currents in external fields that could be present
even in quasi-equilibrium, such as the chiral magnetic (CME) and separation (CSE)
effects, as well as a number of inherently chiral collective modes
called the chiral magnetic (CMW) and vortical (CVW) waves.
Applications of chiral plasmas are truly interdisciplinary, ranging from
hot plasma filling the early Universe, to dense matter in neutron stars,
to electronic band structures in Dirac and Weyl semimetals, to quark-gluon plasma
produced in heavy-ion collisions.
The main focus of this dissertation is a search for traces of chiral physics
in the spectrum of collective modes in chiral plasmas.
I start from relativistic chiral kinetic theory and derive
first- and second-order chiral hydrodynamics.
Then I establish key features of an equilibrium state that describes many
physical chiral systems and use it to find the full spectrum of collective modes
in high-temperature and high-density cases.
Finally, I consider in detail the fate of the two inherently chiral waves, namely
the CMW and the CVW, and determine their detection prospects.
The main results of this dissertation are the formulation of a fully covariant
dissipative chiral hydrodynamics and the calculation of the spectrum of collective
modes in chiral plasmas.
It is found that the dissipative effects and dynamical electromagnetism play
an important role in most cases.
In particular, it is found that both the CMW and the CVW are heavily damped by the usual
Ohmic dissipation in charged plasmas and the diffusion effects in neutral plasmas.
These findings prompt a search for new physical observables in heavy-ion collisions,
as well as a revision of potential applications of chiral theories in
cosmology and solid-state physics.
ContributorsRybalka, Denys (Author) / Shovkovy, Igor (Thesis advisor) / Lunardini, Cecilia (Committee member) / Timmes, Francis (Committee member) / Vachaspati, Tanmay (Committee member) / Arizona State University (Publisher)
Created2019
Description
In the first part of this thesis, we use the generalized Landau-level represen-
tation to study the effect of screening on the properties of the graphene quantum Hall states with integer filling factors. The analysis is performed in the low-energy Dirac model in the mean-field approximation, in which the long-range Coulomb in- teraction is modified by the one-loop static screening effects. The solutions demon- strate that static screening leads to a substantial suppression of the gap parameters in the quantum Hall states with a broken U (4) flavor symmetry. The results of the temperature dependence of the energy gaps mimic well the temperature dependence of the activation energies measured in experiment. The Landau-level running of the quasiparticle dynamical parameters could be tested via optical studies of the integer quantum Hall states.
In the second part, by using the generalized Landau-level representation, we study the interaction induced chiral asymmetry in cold QED plasma beyond the weak-field approximation. The chiral shift and the parity-even chiral chemical potential function are obtained numerically and are found peaking near the Fermi surface and increases and decreases with the Landau level index, respectively. The results are used to quantify the chiral asymmetry of the Fermi surface in dense QED matter. The chiral asymmetry appears to be rather small even in the strongest mag- netic fields and at the highest stellar densities. However, the analogous asymmetry can be substantial in the case of dense quark matter.
tation to study the effect of screening on the properties of the graphene quantum Hall states with integer filling factors. The analysis is performed in the low-energy Dirac model in the mean-field approximation, in which the long-range Coulomb in- teraction is modified by the one-loop static screening effects. The solutions demon- strate that static screening leads to a substantial suppression of the gap parameters in the quantum Hall states with a broken U (4) flavor symmetry. The results of the temperature dependence of the energy gaps mimic well the temperature dependence of the activation energies measured in experiment. The Landau-level running of the quasiparticle dynamical parameters could be tested via optical studies of the integer quantum Hall states.
In the second part, by using the generalized Landau-level representation, we study the interaction induced chiral asymmetry in cold QED plasma beyond the weak-field approximation. The chiral shift and the parity-even chiral chemical potential function are obtained numerically and are found peaking near the Fermi surface and increases and decreases with the Landau level index, respectively. The results are used to quantify the chiral asymmetry of the Fermi surface in dense QED matter. The chiral asymmetry appears to be rather small even in the strongest mag- netic fields and at the highest stellar densities. However, the analogous asymmetry can be substantial in the case of dense quark matter.
ContributorsXia, Lifang, Ph.D (Author) / Shovkovy, Igor (Thesis advisor) / Lebed, Richard (Committee member) / Schmidt, Kevin (Committee member) / Damien, Easson (Committee member) / Arizona State University (Publisher)
Created2016