29 research outputs found
Comagnetometer probes of dark matter and new physics
We discuss the use of comagnetometry in studying new physics that couples to
fermionic spin. Modern comagnetometry is -- in absolute energy units -- the
most sensitive experimental technique for measuring the energy difference
between quantum states, reaching sensitivities in the eV range. The
technique suppresses the magnetic interactions of the spins, making searches
for non-standard-model interactions possible. Many implementations have been
developed and optimized for various uses. New physics scenarios which can be
probed with comagnetometers include: EDMs, violations of Lorentz invariance,
Goldstone bosons of new high-energy symmetries, CP-violating long-range forces,
and axionic dark matter. We consider the prospects for improvements in the
technique, and show -- based purely on signal-to-noise ratio with existing
technology -- that there is room for several orders of magnitude in further
improvement. We also evaluate several sources of systematic error and
instability that may limit improvements.Comment: Submitted to Journal of Quantum Science and Technology. Version 1 is
the manuscript resubmitted following referee reports. Pending final
acceptanc
Fast Evaluation of Feynman Diagrams
We develop a new representation for the integrals associated with Feynman
diagrams. This leads directly to a novel method for the numerical evaluation of
these integrals, which avoids the use of Monte Carlo techniques. Our approach
is based on based on the theory of generalized sinc () functions,
from which we derive an approximation to the propagator that is expressed as an
infinite sum. When the propagators in the Feynman integrals are replaced with
the approximate form all integrals over internal momenta and vertices are
converted into Gaussians, which can be evaluated analytically. Performing the
Gaussians yields a multi-dimensional infinite sum which approximates the
corresponding Feynman integral. The difference between the exact result and
this approximation is set by an adjustable parameter, and can be made
arbitrarily small. We discuss the extraction of regularization independent
quantities and demonstrate, both in theory and practice, that these sums can be
evaluated quickly, even for third or fourth order diagrams. Lastly, we survey
strategies for numerically evaluating the multi-dimensional sums. We illustrate
the method with specific examples, including the the second order sunset
diagram from quartic scalar field theory, and several higher-order diagrams. In
this initial paper we focus upon scalar field theories in Euclidean spacetime,
but expect that this approach can be generalized to fields with spin.Comment: uses feynmp macros; v2 contains improved description of
renormalization, plus other minor change
Phenomenology of Quantum Gravity and its Possible Role in Neutrino Anomalies
New phenomenological models of Quantum Gravity have suggested that a
Lorentz-Invariant discrete spacetime structure may become manifest through a
nonstandard coupling of matter fields and spacetime curvature. On the other
hand, there is strong experimental evidence suggesting that neutrino
oscillations cannot be described by simply considering neutrinos as massive
particles. In this manuscript we motivate and construct one particular
phenomenological model of Quantum Gravity that could account for the so-called
neutrino anomalies.Comment: For the proceedings of "Relativity and Gravitation: 100 Years after
Einstein in Prague" (June 2012, Prague
US Cosmic Visions: New Ideas in Dark Matter 2017: Community Report
This white paper summarizes the workshop "U.S. Cosmic Visions: New Ideas in Dark Matter" held at University of Maryland on March 23-25, 2017