88 research outputs found
An Adynamical, Graphical Approach to Quantum Gravity and Unification
We use graphical field gradients in an adynamical, background independent
fashion to propose a new approach to quantum gravity and unification. Our
proposed reconciliation of general relativity and quantum field theory is based
on a modification of their graphical instantiations, i.e., Regge calculus and
lattice gauge theory, respectively, which we assume are fundamental to their
continuum counterparts. Accordingly, the fundamental structure is a graphical
amalgam of space, time, and sources (in parlance of quantum field theory)
called a "spacetimesource element." These are fundamental elements of space,
time, and sources, not source elements in space and time. The transition
amplitude for a spacetimesource element is computed using a path integral with
discrete graphical action. The action for a spacetimesource element is
constructed from a difference matrix K and source vector J on the graph, as in
lattice gauge theory. K is constructed from graphical field gradients so that
it contains a non-trivial null space and J is then restricted to the row space
of K, so that it is divergence-free and represents a conserved exchange of
energy-momentum. This construct of K and J represents an adynamical global
constraint between sources, the spacetime metric, and the energy-momentum
content of the element, rather than a dynamical law for time-evolved entities.
We use this approach via modified Regge calculus to correct proper distance in
the Einstein-deSitter cosmology model yielding a fit of the Union2 Compilation
supernova data that matches LambdaCDM without having to invoke accelerating
expansion or dark energy. A similar modification to lattice gauge theory
results in an adynamical account of quantum interference.Comment: 47 pages text, 14 figures, revised per recent results, e.g., dark
energy result
Why the Tsirelson Bound? Bub's Question and Fuchs' Desideratum
To answer Wheeler's question "Why the quantum?" via quantum information
theory according to Bub, one must explain both why the world is quantum rather
than classical and why the world is quantum rather than superquantum, i.e.,
"Why the Tsirelson bound?" We show that the quantum correlations and quantum
states corresponding to the Bell basis states, which uniquely produce the
Tsirelson bound for the Clauser-Horne-Shimony-Holt quantity, can be derived
from conservation per no preferred reference frame (NPRF). A reference frame in
this context is defined by a measurement configuration, just as with the light
postulate of special relativity. We therefore argue that the Tsirelson bound is
ultimately based on NPRF just as the postulates of special relativity. This
constraint-based/principle answer to Bub's question addresses Fuchs'
desideratum that we "take the structure of quantum theory and change it from
this very overt mathematical speak ... into something like [special
relativity]." Thus, the answer to Bub's question per Fuchs' desideratum is,
"the Tsirelson bound obtains due to conservation per NPRF."Comment: Contains corrections to the published versio
Answering Mermin's Challenge with Conservation per No Preferred Reference Frame
In 1981, Mermin published a now famous paper titled, "Bringing home the
atomic world: Quantum mysteries for anybody" that Feynman called, "One of the
most beautiful papers in physics that I know." Therein, he presented the
"Mermin device" that illustrates the conundrum of quantum entanglement per the
Bell spin states for the "general reader." He then challenged the "physicist
reader" to explain the way the device works "in terms meaningful to a general
reader struggling with the dilemma raised by the device." Herein, we show how
"conservation per no preferred reference frame (NPRF)" answers that challenge.
In short, the explicit conservation that obtains for Alice and Bob's
Stern-Gerlach spin measurement outcomes in the same reference frame holds only
on average in different reference frames, not on a trial-by-trial basis. This
conservation is SO(3) invariant in the relevant symmetry plane in real space
per the SU(2) invariance of its corresponding Bell spin state in Hilbert space.
Since NPRF is also responsible for the postulates of special relativity, and
therefore its counterintuitive aspects of time dilation and length contraction,
we see that the symmetry group relating non-relativistic quantum mechanics and
special relativity via their "mysteries" is the restricted Lorentz group.Comment: 18 pages, 9 figures. This version as revised and resubmitted to
Scientific Report
End of a Dark Age?
We argue that dark matter and dark energy phenomena associated with galactic
rotation curves, X-ray cluster mass profiles, and type Ia supernova data can be
accounted for via small corrections to idealized general relativistic spacetime
geometries due to disordered locality. Accordingly, we fit THINGS rotation
curve data rivaling modified Newtonian dynamics, ROSAT/ASCA X-ray cluster mass
profile data rivaling metric-skew-tensor gravity, and SCP Union2.1 SN Ia data
rivaling CDM without non-baryonic dark matter or a cosmological
constant. In the case of dark matter, we geometrically modify proper mass
interior to the Schwarzschild solution. In the case of dark energy, we modify
proper distance in Einstein-deSitter cosmology. Therefore, the phenomena of
dark matter and dark energy may be chimeras created by an errant belief that
spacetime is a differentiable manifold rather than a disordered graph.Comment: This version was accepted for publication in the International
Journal of Modern Physics D; revised version of an essay that won Honorable
Mention in the Gravity Research Foundation 2016 Awards for Essays on
Gravitation. 10 pages, 3 figures. arXiv admin note: text overlap with
arXiv:1509.0928
The Missing Mass Problem as a Manifestation of GR Contextuality
In Newtonian gravity, mass is an intrinsic property of matter while in
general relativity (GR), mass is a contextual property of matter, i.e., matter
can simultaneously possess two different values of mass when it is responsible
for two different spatiotemporal geometries. Herein, we explore the possibility
that the astrophysical missing mass attributed to non-baryonic dark matter (DM)
actually obtains because we have been assuming the Newtonian view of mass
rather than the GR view. Since an exact GR solution for realistic astrophysical
situations is not feasible, we explore GR-motivated ansatzes relating proper
mass and dynamic mass for one and the same baryonic matter, as justified by GR
contextuality. We consider four GR alternatives and find that the GR ansatz
motivated by metric perturbation theory works well in fitting galactic rotation
curves (THINGS data), the mass profiles of X-ray clusters (ROSAT and ASCA data)
and the angular power spectrum of the cosmic microwave background (CMB, Planck
2015 data) without DM. We compare our galactic rotation curve fits to modified
Newtonian dynamics (MOND), Burkett halo DM and Navarro-Frenk-White (NFW) halo
DM. We compare our X-ray cluster mass profile fits to metric skew-tensor
gravity (MSTG) and core-modified NFW DM. We compare our CMB angular power
spectrum fit to scalar-tensor-vector gravity (STVG) and CDM. Overall,
we find our fits to be comparable to those of MOND, MSTG, STVG, CDM,
Burkett, and NFW. We present and discuss correlations and trends for the best
fit values of our fitting parameters. For the most part, the correlations are
consistent with well-established results at all scales, which is perhaps
surprising given the simple functional form of the GR ansatz.Comment: 18 pages text. Twice revised per referee/reviewer comments. Fit of
CMB angular power spectrum and dark matter halo fits adde
"Mysteries" of Modern Physics and the Fundamental Constants c, h, and G
We review how the kinematic structures of special relativity and quantum mechanics both stem from the relativity principle, i.e., "no preferred reference frame" (NPRF). Essentially, NPRF applied to the measurement of the speed of light c gives the light postulate and leads to the geometry of Minkowski space, while NPRF applied to the measurement of Planck's constant h gives "average-only" projection and leads to the denumerable-dimensional Hilbert space of quantum mechanics. These kinematic structures contain the counterintuitive aspects ("mysteries") of time dilation, length contraction, and quantum entanglement. In this essay, we extend the application of NPRF to the gravitational constant G and show that it leads to the "mystery" of the contextuality of mass in general relativity. Thus, we see an underlying coherence and integrity in modern physics via its "mysteries" and the fundamental constants c, h, and G. It is well known that Minkowski and Einstein were greatly influenced by David Hilbert in their development of special relativity and general relativity, respectively, but relating those theories to quantum mechanics via its non-Boolean Hilbert space kinematics is perhaps surprising.Quanta 2022; 11: 5–14
Use of Slow Strain Rate Tensile Testing to Assess the Ability of Several Superalloys to Resist Environmentally-Assisted Intergranular Cracking
Intergranular fatigue crack initiation and growth due to environmental degradation, especially at notched features, can often limit the fatigue life of disk superalloys at high temperatures. For clear comparisons, the effects of alloy composition on cracking in air needs to be understood and compared separately from variables associated with notches and cracks such as effective stress concentration, plastic flow, stress relaxation, and stress redistribution. The objective of this study was to attempt using simple tensile tests of specimens with uniform gage sections to compare the effects of varied alloy composition on environment-assisted cracking of several powder metal and cast and wrought superalloys including ME3, LSHR, Udimet 720(TradeMark) ATI 718Plus(Registered TradeMark) alloy, Haynes 282(Trademark), and Inconel 740(TradeMark) Slow and fast strain-rate tensile tests were found to be a useful tool to compare propensities for intergranular surface crack initiation and growth. The effects of composition and heat treatment on tensile fracture strain and associated failure modes were compared. Environment interactions were determined to often limit ductility, by promoting intergranular surface cracking. The response of various superalloys and heat treatments to slow strain rate tensile testing varied substantially, showing that composition and microstructure can significantly influence environmental resistance to cracking
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