2,603 research outputs found
Interferometers as Probes of Planckian Quantum Geometry
A theory of position of massive bodies is proposed that results in an
observable quantum behavior of geometry at the Planck scale, . Departures
from classical world lines in flat spacetime are described by Planckian
noncommuting operators for position in different directions, as defined by
interactions with null waves. The resulting evolution of position wavefunctions
in two dimensions displays a new kind of directionally-coherent quantum noise
of transverse position. The amplitude of the effect in physical units is
predicted with no parameters, by equating the number of degrees of freedom of
position wavefunctions on a 2D spacelike surface with the entropy density of a
black hole event horizon of the same area. In a region of size , the effect
resembles spatially and directionally coherent random transverse shear
deformations on timescale with typical amplitude . This quantum-geometrical "holographic noise" in position is not
describable as fluctuations of a quantized metric, or as any kind of
fluctuation, dispersion or propagation effect in quantum fields. In a Michelson
interferometer the effect appears as noise that resembles a random Planckian
walk of the beamsplitter for durations up to the light crossing time. Signal
spectra and correlation functions in interferometers are derived, and predicted
to be comparable with the sensitivities of current and planned experiments. It
is proposed that nearly co-located Michelson interferometers of laboratory
scale, cross-correlated at high frequency, can test the Planckian noise
prediction with current technology.Comment: 23 pages, 6 figures, Latex. To appear in Physical Review
New strong sector, odd-parity processes, and the Tevatron
The color-octet isosinglet "rho" of a new strong-interaction sector is
readily produced in ppbar collisions. Its odd-parity decay to an "eta" and a
gluon may exceed its decay rate to dijets. At center of mass energies
sufficiently greater than the colored "rho" mass, the odd-parity production of
("omega" + colored "eta") or ("rho" + colored "pion") may be comparable to
ttbar production. Considering that the "omega" has a dominant odd-parity decay
mode, we end up with (Z, W, or gamma) + 4 jet events with two of the jets
containing b or bbar.Comment: 8 pages, uuencoded PS file, try ghostscript or direct printing rather
than ghostview, PS file of paper without figure is available on WWW at
http://bigmac2.physics.utoronto.ca/BHpapers.htm
Investing in Mobility: Freight Transport in the Hudson Region
Proposes a framework for assessing alternative investments in freight rail, highway, and transit capacity that would increase the ability to improve mobility and air quality in the New York metropolitan area
The Theory of a Quantum Noncanonical Field in Curved Spacetimes
Much attention has been recently devoted to the possibility that quantum
gravity effects could lead to departures from Special Relativity in the form of
a deformed Poincar\`e algebra. These proposals go generically under the name of
Doubly or Deformed Special Relativity (DSR). In this article we further explore
a recently proposed class of quantum field theories, involving noncanonically
commuting complex scalar fields, which have been shown to entail a DSR-like
symmetry. An open issue for such theories is whether the DSR-like symmetry has
to be taken as a physically relevant symmetry, or if in fact the "true"
symmetries of the theory are just rotations and translations while boost
invariance has to be considered broken. We analyze here this issue by extending
the known results to curved spacetime under both of the previous assumptions.
We show that if the symmetry of the free theory is taken to be a DSR-like
realization of the Poincar\'e symmetry, then it is not possible to render such
a symmetry a gauge symmetry of the curved physical spacetime. However, it is
possible to introduce an auxiliary spacetime which allows to describe the
theory as a standard quantum field theory in curved spacetime. Alternatively,
taking the point of view that the noncanonical commutation of the fields
actually implies a breakdown of boost invariance, the physical spacetime
manifold has to be foliated in surfaces of simultaneity and the field theory
can be coupled to gravity by making use of the ADM prescription.Comment: 9 pages, no figure
Lorentz Violating Inflation
We explore the impact of Lorentz violation on the inflationary scenario. More
precisely, we study the inflationary scenario in the scalar-vector-tensor
theory where the vector is constrained to be unit and time like. It turns out
that the Lorentz violating vector affects the dynamics of the chaotic
inflationary model and divides the inflationary stage into two parts; the
Lorentz violating stage and the standard slow roll stage. We show that the
universe is expanding as an exact de Sitter spacetime in the Lorentz violating
stage although the inflaton field is rolling down the potential. Much more
interestingly, we find exact Lorentz violating inflationary solutions in the
absence of the inflaton potential. In this case, the inflation is completely
associated with the Lorentz violation. We also mention some consequences of
Lorentz violating inflation which can be tested by observations.Comment: 7 pages, 1 figur
State of the Union: The Poverty and Inequality Report 2016
The Stanford Center on Poverty and Inequality (CPI), one of the country's three federally-funded poverty centers, is a nonpartisan organization dedicated to monitoring trends in poverty and inequality, examining what is driving those trends, and developing science-based policy on poverty and inequality. We present here our third annual report examining the "state of the union" on poverty, inequality, and labor market outcomes.The purpose of establishing this annual series of reports is to ensure that critical facts on poverty and inequality enjoy the same visibility as other indicators of the country's health. There are of course all manner of analyses that take on separately such issues as poverty, employment, income inequality, health inequality, economic mobility, or educational access. This report instead provides a unified analysis that brings together evidence across these and other domains and thus allows for a comprehensive assessment of where the country stands
Non-local on-shell field redefinition for the SME
This work instigates a study of non-local field mappings within the Lorentz-
and CPT-violating Standard-Model Extension (SME). An example of such a mapping
is constructed explicitly, and the conditions for the existence of its inverse
are investigated. It is demonstrated that the associated field redefinition can
remove b-type Lorentz violation from free SME fermions in certain situations.
These results are employed to obtain explicit expressions for the corresponding
Lorentz-breaking momentum-space eigenspinors and their orthogonality relations.Comment: 12 pages, REVTeX
Lorentz-symmetry violating decays in a medium
Various decay processes, such as the decay of a spin-1 particle into two
photons or the gravitational decay of a spin-1/2 fermion, are forbidden in the
vacuum by a combination of requirements, including angular momentum
conservation, Lorentz invariance and gauge invariance. We show that such
processes can occur in a medium, such as a thermal background of particles,
even if it is homogeneous and isotropic. We carry out a model-independent
analysis of the vertex function for such processes in terms of a set of form
factors, and show that the amplitude can be non-zero while remaining consistent
with the symmetry principles mentioned above. The results simulate Lorentz
symmetry violating effects, although in this case they arise from completely
Lorentz-invariant physics.Comment: 16 pages, Latex, no figure
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