3,595 research outputs found
Doing Algebra over an Associative Algebra
A finite-dimensional unital and associative algebra over , or
what we shall call simply "an algebra" in this paper for short, generalities
the construction by which we derive the complex numbers by "adjoining an
element " to and imposing the relation . In this
paper, we examine some of the elementary algebraic properties of such algebras,
how they break-down when compared to standard grade-school algebra, and discuss
how such properties are relevant to other areas of our research regarding
algebras, such as the -calculus and the theory of
-ODEs.Comment: Finished draft of work primarily done during the summer of 201
Logarithms Over a Real Associative Algebra
Extending the work of Freese and Cook, which develop the basic theory of
calculus and power series over real associative algebras, we examine what can
be said about the logarithmic functions over an algebra. In particular, we find
that for any multiplicative unital nil algebra the exponential function is
injective, and hence the algebra has a unique logarithm on the image of the
exponential. We extend this result to show that for a large class of algebras,
the logarithms behave incredibly similarly to the logarithms over the real and
complex numbers depending on if they are "Type-R" or "Type-C" algebras.Comment: 15 pages. Final draft based on research that was primarily conducted
in the summer of 201
Generalized Trigonometric Functions over Associative Algebras
Extending the work of Freese, we further develop the theory of generalized
trigonometric functions. In particular, we study to what extent the notion of
polar form for the complex numbers may be generalized to arbitrary associative
algebras, and how the general trigonometric functions may be used to give
particularly elegant formulas for the logarithm over an algebra. Finally, we
close with an array of open questions relating to this line of inquiry.Comment: 15 pages. Final draft based primarily on work that was done during
the summer of 201
Quantum spin transport and dynamics through a novel F/N junction
We study the spin transport in the low temperature regime (often referred to
as the precession-dominated regime) between a ferromagnetic Fermi liquid (FFL)
and a normal metal metallic Fermi liquid (NFL), also known as the F/N junction,
which is considered as one of the most basic spintronic devices. In particular,
we explore the propagation of spin waves and transport of magnetization through
the interface of the F/N junction where nonequilibrium spin polarization is
created on the normal metal side of the junction by electrical spin injection.
We calculate the probable spin wave modes in the precession-dominated regime on
both sides of the junction especially on the NFL side where the system is out
of equilibrium. Proper boundary conditions at the interface are introduced to
establish the transport of the spin properties through the F/N junction. A
possible transmission conduction electron spin resonance (CESR) experiment is
suggested on the F/N junction to see if the predicted spin wave modes could
indeed propagate through the junction. Potential applications based on this
novel spin transport feature of the F/N junction are proposed in the end.Comment: 7 pages, 2 figure
Spin Orbit Magnetism and Unconventional Superconductivity
We find an exotic spin excitation in a magnetically ordered system with spin
orbit magnetism in 2D, where the order parameter has a net spin current and no
net magnetization. Starting from a Fermi liquid theory, similar to that for a
weak ferromagnet, we show that this excitation emerges from an exotic magnetic
Fermi liquid state that is protected by a generalized Pomeranchuck condition.
We derive the propagating mode using the Landau kinetic equation, and find that
the dispersion of the mode has a behavior in leading order in 2D. We
find an instability toward superconductivity induced by this exotic mode, and a
further analysis based on the forward scattering sum rule strongly suggests
that this superconductivity has p-wave pairing symmetry. We perform similar
studies in the 3D case, with a slightly different magnetic system and find that
the mode leads to a Lifshitz-like instability most likely toward an
inhomogeneous magnetic state in one of the phases.Comment: 5 pages, 3 figure
Non-Analytic Contributions to the Self-Energy and the Thermodynamics of Two-Dimensional Fermi Liquids
We calculate the entropy of a two-dimensional Fermi Liquid(FL) using a model
with a contact interaction between fermions. We find that there are
contributions to the entropy from interactions separate from those due to the
collective modes. These contributions arise from non-analytic corrections
to the real part of the self-energy which may be calculated from the leading
log dependence of the imaginary part of the self-energy through the
Kramers-Kronig relation. We find no evidence of a breakdown in Fermi Liquid
theory in 2D and conclude that FL in 2D are similar to 3D FL's.Comment: 12 pages (RexTex, no figures
Introduction to the Theory of -ODEs
We study the theory of ordinary differential equations over a commutative
finite dimensional real associative unital algebra . We call such
problems -ODEs. If a function is real differentiable and its
differential is in the regular representation of then we say the
function is -differentiable. In this paper, we prove an existence
and uniqueness theorem, derive Abel's formula for the Wronskian and establish
the existence of a fundamental solution set for many -ODEs. We
show the Wronskian of a fundamental solution set cannot be a divisor of zero.
Three methods to solve nondegenerate constant coefficient -ODE are
given. First, we show how zero-divisors complicate solution by factorization of
operators. Second, isomorphisms to direct product are shown to produce
interesting solutions. Third, our extension technique is shown to solve any
nondegenerate -ODE; we find a fundamental solution set by
selecting the component functions of the exponential on the characteristic
extension algebra. The extension technique produces all of the elementary
functions seen in the usual analysis by a bit of abstract algebra applied to
the appropriate exponential function. On the other hand, we show how
zero-divisors destroy both existence and uniqueness in degenerate
-ODEs. We also study the Cauchy Euler problem for
-Calculus and indicate how we may solve first order
-ODEs.Comment: 33 page
Approaching Pomeranchuk Instabilities from Ordered Phase: A Crossing-symmetric Equation Method
We explore features of a 3D Fermi liquid near generalized Pomeranchuk
instabilities using a tractable crossing symmetric equation method. We approach
the instabilities from the ordered ferromagnetic phase. We find quantum
multi-criticality as approach to the ferromagnetic instability drives
instability in other channel(s). It is found that a charge nematic instability
precedes and is driven by Pomeranchuk instabilities in both the l = 0 spin and
density channels.Comment: 16 pages, 7 figure
Exotic quantum statistics and thermodynamics from a number-conserving theory of Majorana fermions
We propose a closed form for the statistical distribution of non-interacting
Majorana fermions at low temperature. Majorana particles often appear in the
contemporary many-body literature in the Kitaev, Fu-Kane, or Sachdev-Ye-Kitaev
models, where the Majorana condition of self-conjugacy immediately results in
nonconserved particle number, non-trivial braiding statistics, and the absence
of a noninteracting limit. We deviate from this description and instead
consider a gas of noninteracting, spin-1/2 Majorana fermions that obey the
spin-statistics theorem via imposing a condensed matter analog of momentum
conservation. This allows us to build a quantum statistical theory of the
Majorana system in the low temperature, low density limit without the need to
account for strong fluctuations in the particle number. A combinatorial
analysis leads to a configurational entropy which deviates from the fermionic
result with an increasing number of available microstates. A number-conserving
Majorana distribution function is derived which shows signatures of a
sharply-defined Fermi surface at finite temperatures. Such a distribution is
then re-derived from a microscopic model in the form of a modified Kitaev chain
with a bosonic pair interaction. The thermodynamics of this free Majorana
system is found to be nearly identical to that of a free Fermi gas, except now
distinguished by a two-fold ground state degeneracy and, subsequently, a
residual entropy at zero temperature. Despite clear differences with the
anyonic or Sachdev-Ye-Kitaev models, we nevertheless find surprising agreement
between our theory and experimental signatures of Majorana excitations in
several materials. Experimental realization of our exactly solvable model is
also discussed in the realm of astrophysical and high-energy phenomena.Comment: 66 pages, 7 figures, 5 table
No Evidence for Lunar Transit in New Analysis of Hubble Space Telescope Observations of the Kepler-1625 System
Observations of the Kepler-1625 system with the Kepler and Hubble Space
Telescopes have suggested the presence of a candidate exomoon, Kepler-1625b I,
a Neptune-radius satellite orbiting a long-period Jovian planet. Here we
present a new analysis of the Hubble observations, using an independent data
reduction pipeline. We find that the transit light curve is well fit with a
planet-only model, with a best-fit equal to 1.01. The addition of
a moon does not significantly improve the fit quality. We compare our results
directly with the original light curve from Teachey & Kipping (2018), and find
that we obtain a better fit to the data using a model with fewer free
parameters (no moon). We discuss possible sources for the discrepancy in our
results, and conclude that the lunar transit signal found by Teachey & Kipping
(2018) was likely an artifact of the data reduction. This finding highlights
the need to develop independent pipelines to confirm results that push the
limits of measurement precision.Comment: 7 pages, 5 figures, accepted to ApJ
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