790 research outputs found
The surprising influence of late charged current weak interactions on Big Bang Nucleosynthesis
The weak interaction charged current processes (, , ) interconvert neutrons and protons in the early universe and
have significant influence on Big Bang Nucleosynthesis (BBN) light-element
abundance yields, particulary that for . We demonstrate that the
influence of these processes is still significant even when they operate well
below temperatures usually invoked for "weak freeze-out,"
and in fact down nearly into the alpha-particle formation epoch (). This physics is correctly captured in commonly used BBN
codes, though this late-time, low-temperature persistent effect of the
isospin-changing weak processes, and the sensitivity of the associated rates to
lepton energy distribution functions and blocking factors are not widely
appreciated. We quantify this late-time influence by analyzing weak interaction
rate dependence on the neutron lifetime, lepton energy distribution functions,
entropy, the proton-neutron mass difference, and Hubble expansion rate. The
effects we point out here render BBN a keen probe of any beyond-standard-model
physics that alters lepton number/energy distributions, even subtly, in epochs
of the early universe all the way down to near .Comment: 27 pages, 8 figure
Insights into neutrino decoupling gleaned from considerations of the role of electron mass
We present calculations showing how electron rest mass influences entropy
flow, neutrino decoupling, and Big Bang Nucleosynthesis (BBN) in the early
universe. To elucidate this physics and especially the sensitivity of BBN and
related epochs to electron mass, we consider a parameter space of rest mass
values larger and smaller than the accepted vacuum value. Electromagnetic
equilibrium, coupled with the high entropy of the early universe, guarantees
that significant numbers of electron-positron pairs are present, and dominate
over the number of ionization electrons to temperatures much lower than the
vacuum electron rest mass. Scattering between the electrons-positrons and the
neutrinos largely controls the flow of entropy from the plasma into the
neutrino seas. Moreover, the number density of electron-positron-pair targets
can be exponentially sensitive to the effective in-medium electron mass. This
entropy flow influences the phasing of scale factor and temperature, the
charged current weak-interaction-determined neutron-to-proton ratio, and the
spectral distortions in the relic neutrino energy spectra. Our calculations
show the sensitivity of the physics of this epoch to three separate effects:
finite electron mass, finite-temperature quantum electrodynamic (QED) effects
on the plasma equation of state, and Boltzmann neutrino energy transport. The
ratio of neutrino to plasma component energy scales manifests in Cosmic
Microwave Background (CMB) observables, namely the baryon density and the
radiation energy density, along with the primordial helium and deuterium
abundances. Our results demonstrate how the treatment of in-medium electron
mass (i.e., QED effects) could translate into an important source of
uncertainty in extracting neutrino and beyond-standard-model physics limits
from future high-precision CMB data.Comment: 32 pages, 8 figures, 1 table. Version accepted by Nuclear Physics
Majorana Neutrino Magnetic Moment and Neutrino Decoupling in Big Bang Nucleosynthesis
We examine the physics of the early universe when Majorana neutrinos
(electron neutrino, muon neutrino, tau neutrino) possess transition magnetic
moments. These extra couplings beyond the usual weak interaction couplings
alter the way neutrinos decouple from the plasma of electrons/positrons and
photons. We calculate how transition magnetic moment couplings modify neutrino
decoupling temperatures, and then use a full weak, strong, and electromagnetic
reaction network to compute corresponding changes in Big Bang Nucleosynthesis
abundance yields. We find that light element abundances and other cosmological
parameters are sensitive to magnetic couplings on the order of 10^{-10} Bohr
magnetons. Given the recent analysis of sub-MeV Borexino data which constrains
Majorana moments to the order of 10^{-11} Bohr magnetons or less, we find that
changes in cosmological parameters from magnetic contributions to neutrino
decoupling temperatures are below the level of upcoming precision observations.Comment: 19 pages, 9 figure
Probing neutrino physics with a self-consistent treatment of the weak decoupling, nucleosynthesis, and photon decoupling epochs
We show that a self-consistent and coupled treatment of the weak decoupling,
big bang nucleosynthesis, and photon decoupling epochs can be used to provide
new insights and constraints on neutrino sector physics from high-precision
measurements of light element abundances and cosmic microwave background
observables. Implications of beyond-standard-model physics in cosmology,
especially within the neutrino sector, are assessed by comparing predictions
against five observables: the baryon energy density, helium abundance,
deuterium abundance, effective number of neutrinos, and sum of the light
neutrino mass eigenstates. We give examples for constraints on dark radiation,
neutrino rest mass, lepton numbers, and scenarios for light and heavy sterile
neutrinos.Comment: 29 pages, 10 figure
Neutrino energy transport in weak decoupling and big bang nucleosynthesis
We calculate the evolution of the early universe through the epochs of weak
decoupling, weak freeze-out and big bang nucleosynthesis (BBN) by
simultaneously coupling a full strong, electromagnetic, and weak nuclear
reaction network with a multi-energy group Boltzmann neutrino energy transport
scheme. The modular structure of our code provides the ability to dissect the
relative contributions of each process responsible for evolving the dynamics of
the early universe in the absence of neutrino flavor oscillations. Such an
approach allows a detailed accounting of the evolution of the ,
, , , , energy
distribution functions alongside and self-consistently with the nuclear
reactions and entropy/heat generation and flow between the neutrino and
photon/electron/positron/baryon plasma components. This calculation reveals
nonlinear feedback in the time evolution of neutrino distribution functions and
plasma thermodynamic conditions (e.g., electron-positron pair densities), with
implications for: the phasing between scale factor and plasma temperature; the
neutron-to-proton ratio; light-element abundance histories; and the
cosmological parameter \neff. We find that our approach of following the time
development of neutrino spectral distortions and concomitant entropy production
and extraction from the plasma results in changes in the computed value of the
BBN deuterium yield. For example, for particular implementations of quantum
corrections in plasma thermodynamics, our calculations show a increase
in deuterium. These changes are potentially significant in the context of
anticipated improvements in observational and nuclear physics uncertainties.Comment: 37 pages, 12 Figures, 6 Table
Flags and Friends
Our team worked with Orange County’s Special Olympics Flag Football team. We helped coach practices, organized drills, and supported the team at games/tournaments. Through this experience we got the chance to get further involved in our community through doing something we were passionate about. We learned how to apply the different principles of leadership to our mission of fostering an environment that drives inclusion and skill-building. These principles include loving others, extending ourselves, and leading with authority. We went into this experience viewing it as a school project. However, after a few practices, we started developing individual connections with players and coaches and found enjoyment in the overall process. Over the course of our time with the team, we watched their skills improve and friendships strengthen.https://stars.library.ucf.edu/hip-2023fall/1062/thumbnail.jp
Ruled Laguerre minimal surfaces
A Laguerre minimal surface is an immersed surface in the Euclidean space
being an extremal of the functional \int (H^2/K - 1) dA. In the present paper,
we prove that the only ruled Laguerre minimal surfaces are up to isometry the
surfaces R(u,v) = (Au, Bu, Cu + D cos 2u) + v (sin u, cos u, 0), where A, B, C,
D are fixed real numbers. To achieve invariance under Laguerre transformations,
we also derive all Laguerre minimal surfaces that are enveloped by a family of
cones. The methodology is based on the isotropic model of Laguerre geometry. In
this model a Laguerre minimal surface enveloped by a family of cones
corresponds to a graph of a biharmonic function carrying a family of isotropic
circles. We classify such functions by showing that the top view of the family
of circles is a pencil.Comment: 28 pages, 9 figures. Minor correction: missed assumption (*) added to
Propositions 1-2 and Theorem 2, missed case (nested circles having nonempty
envelope) added in the proof of Pencil Theorem 4, missed proof that the arcs
cut off by the envelope are disjoint added in the proof of Lemma
A smooth introduction to the wavefront set
The wavefront set provides a precise description of the singularities of a
distribution. Because of its ability to control the product of distributions,
the wavefront set was a key element of recent progress in renormalized quantum
field theory in curved spacetime, quantum gravity, the discussion of time
machines or quantum energy inequalitites. However, the wavefront set is a
somewhat subtle concept whose standard definition is not easy to grasp. This
paper is a step by step introduction to the wavefront set, with examples and
motivation. Many different definitions and new interpretations of the wavefront
set are presented. Some of them involve a Radon transform.Comment: 29 pages, 7 figure
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