Matching Items (4)
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- All Subjects: cosmic strings
- All Subjects: Nuclear physics and radiation
- Creators: Vachaspati, Tanmay
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
Proton radiotherapy has recently become a popular form of cancer treatment. For maximum effectiveness, accurate models are needed to calculate proton angular scattering and energy loss. Scattering events are statistically independent and may be calculated from the effective number of events per reciprocal multiple scattering angle or energy loss. It is shown that multiple scattering distributions from Molière’s scattering law can be convolved by depth for accurate numerical calculation of angular distributions in several example materials. This obviates the need for correction factors to the analytic solution and its approximations. It is also shown that numerically solving Molière’s scattering law in terms of the complete (non-small angle) differential cross section and large angle approximations extends the validity of Molière theory to large angles. To calculate probability energy loss distributions, Landau-Vavilov theory is adapted to Fourier transforms and extended to very thick targets through convolution over the probability energy loss distributions in each depth interval. When the depth is expressed in terms of the continuous slowing down approximation (CSDA) the resulting probability energy loss distributions rely on the mean excitation energy as the sole material dependent parameter. Through numerical calculation of the CSDA over the desired energy loss, this allows the energy loss cross section to vary across the distribution and accurately accounts for broadening and skewness for thick targets in a compact manner. An analytic, Fourier transform solution to Vavilov’s integral is shown. A single scattering nuclear model that calculates large angle dose distributions that have a similar functional form to FLUKA (FLUktuierende KAskade) Monte Carlo, is also introduced. For incorporation into Monte Carlo or a treatment planning system, lookup tables of the number of scattering events or cross sections for different clinical energies may be used to determine angular or energy loss distributions.
ContributorsBrosch, Ryan Michael (Author) / Rez, Peter (Thesis advisor) / Alarcon, Ricardo O (Thesis advisor) / Vachaspati, Tanmay (Committee member) / Treacy, Michael M.J. (Committee member) / Arizona State University (Publisher)
Created2022
Description
In this dissertation, I present the results from my recent
investigations into the interactions involving topological defects, such as
magnetic monopoles and strings, that may have been produced in the early
universe. I performed numerical studies on the interactions of twisted
monopole-antimonopole pairs in the 't Hooft-Polyakov model for a range of
values of the scalar to vector mass ratio. Sphaleron solution predicted by
Taubes was recovered, and I mapped out its energy and size as functions of
parameters. I also looked into the production, and decay modes of $U(1)$ gauge
and global strings. I demonstrated that strings can be produced upon evolution
of gauge wavepackets defined within a certain region of parameter space. The
numerical exploration of the decay modes of cosmic string loops led to the
conclusions that string loops emit particle radiation primarily due to kink
collisions, and that their decay time due to these losses is proportional to
$L^p$, where $L$ is the loop length and $p \approx 2$. In contrast, the decay
time due to gravitational radiation scales in proportion to $L$, and I
concluded that particle emission is the primary energy loss mechanism for loops
smaller than a critical length scale, while gravitational losses dominate for
larger loops. In addition, I analyzed the decay of cosmic global string loops
due to radiation of Goldstone bosons and massive scalar ($\chi$) particles.
The length of loops I studied ranges from 200-1000 times the width of the
string core. I found that the lifetime of a loop is approximately $1.4L$. The
energy spectrum of Goldstone boson radiation has a $k^{-1}$ fall off, where $k$
is the wavenumber, and a sharp peak at $k\approx m_\chi/2$, where $m_\chi$ is
the mass of $\chi$. The latter is a new feature and implies a peak at high
energies (MeV-GeV) in the cosmological distribution of QCD axions.
investigations into the interactions involving topological defects, such as
magnetic monopoles and strings, that may have been produced in the early
universe. I performed numerical studies on the interactions of twisted
monopole-antimonopole pairs in the 't Hooft-Polyakov model for a range of
values of the scalar to vector mass ratio. Sphaleron solution predicted by
Taubes was recovered, and I mapped out its energy and size as functions of
parameters. I also looked into the production, and decay modes of $U(1)$ gauge
and global strings. I demonstrated that strings can be produced upon evolution
of gauge wavepackets defined within a certain region of parameter space. The
numerical exploration of the decay modes of cosmic string loops led to the
conclusions that string loops emit particle radiation primarily due to kink
collisions, and that their decay time due to these losses is proportional to
$L^p$, where $L$ is the loop length and $p \approx 2$. In contrast, the decay
time due to gravitational radiation scales in proportion to $L$, and I
concluded that particle emission is the primary energy loss mechanism for loops
smaller than a critical length scale, while gravitational losses dominate for
larger loops. In addition, I analyzed the decay of cosmic global string loops
due to radiation of Goldstone bosons and massive scalar ($\chi$) particles.
The length of loops I studied ranges from 200-1000 times the width of the
string core. I found that the lifetime of a loop is approximately $1.4L$. The
energy spectrum of Goldstone boson radiation has a $k^{-1}$ fall off, where $k$
is the wavenumber, and a sharp peak at $k\approx m_\chi/2$, where $m_\chi$ is
the mass of $\chi$. The latter is a new feature and implies a peak at high
energies (MeV-GeV) in the cosmological distribution of QCD axions.
ContributorsSaurabh, Ayush (Author) / Vachaspati, Tanmay (Thesis advisor) / Lebed, Richard (Committee member) / Baumgart, Matthew (Committee member) / Keeler, Cynthia (Committee member) / Arizona State University (Publisher)
Created2020
Description
In a hypothetical Grand Unified Theory, magnetic monopoles are a particle which would act as a charge carrier for the magnetic force. Evidence of magnetic monopoles has yet to be found and based off of their relatively high mass (4-10 TeV) will be difficult to find with current technology. The goal of my thesis is to mathematically model the magnetic monopole by finding numerical solutions to the equations of motion. In my analysis, I consider four cases: kinks, cosmic strings, global monopoles, and magnetic monopoles. I will also study electromagnetic gauge fields to prepare to include gauge fields in the magnetic monopole case. Numerical solutions are found for the cosmic string and global monopole cases. As expected, the energy is high at small distance r and drops off as r goes to infinity. Currently numerical solutions are being worked towards for electromagnetic gauge fields and the magnetic monopole case.
ContributorsBrown, Taryn (Author) / Vachaspati, Tanmay (Thesis director) / Keeler, Cynthia (Committee member) / Barrett, The Honors College (Contributor) / School of Human Evolution & Social Change (Contributor) / Department of Physics (Contributor) / School of Earth and Space Exploration (Contributor)
Created2022-05