113 research outputs found
Optical calibration hardware for the Sudbury Neutrino Observatory
The optical properties of the Sudbury Neutrino Observatory (SNO) heavy water
Cherenkov neutrino detector are measured in situ using a light diffusing sphere
("laserball"). This diffuser is connected to a pulsed nitrogen/dye laser via
specially developed underwater optical fibre umbilical cables. The umbilical
cables are designed to have a small bending radius, and can be easily adapted
for a variety of calibration sources in SNO. The laserball is remotely
manipulated to many positions in the D2O and H2O volumes, where data at six
different wavelengths are acquired. These data are analysed to determine the
absorption and scattering of light in the heavy water and light water, and the
angular dependence of the response of the detector's photomultiplier tubes.
This paper gives details of the physical properties, construction, and optical
characteristics of the laserball and its associated hardware.Comment: 17 pages, 8 figures, submitted to Nucl. Inst. Meth.
Scalar field in the Bianchi I: Non commutative classical and Quantum Cosmology
Using the ADM formalism in the minisuperspace, we obtain the commutative and
noncommutative exact classical solutions and exact wave function to the
Wheeler-DeWitt equation with an arbitrary factor ordering, for the anisotropic
Bianchi type I cosmological model, coupled to a scalar field, cosmological term
and barotropic perfect fluid. We introduce noncommutative scale factors,
considering that all minisuperspace variables do not commute, so the
symplectic structure was modified. In the classical regime, it is shown that
the anisotropic parameter and the field , for some
value in the cosmological term and noncommutative
parameter, present a dynamical isotropization up to a critical cosmic time
; after this time, the effects of isotropization in the noncommutative
minisuperspace seems to disappear. In the quantum regimen, the probability
density presents a new structure that corresponds to the value of the
noncommutativity parameter.Comment: 17 pages, 6 figures, Acepted in IJT
Noncommutative Self-dual Gravity
Starting from a self-dual formulation of gravity, we obtain a noncommutative
theory of pure Einstein theory in four dimensions. In order to do that, we use
Seiberg-Witten map. It is shown that the noncommutative torsion constraint is
solved by the vanishing of commutative torsion. Finally, the noncommutative
corrections to the action are computed up to second order.Comment: 15+1 pages, LaTeX, no figure
Noncommutative Topological Theories of Gravity
The possibility of noncommutative topological gravity arising in the same
manner as Yang-Mills theory is explored. We use the Seiberg-Witten map to
construct such a theory based on a SL(2,C) complex connection, from which the
Euler characteristic and the signature invariant are obtained. This gives us a
way towards the description of noncommutative gravitational instantons as well
as noncommutative local gravitational anomalies.Comment: 17+1 pages, LaTeX, no figures, some clarifications, comments and
references added, style improve
Birkhoff's theorem in the f(T) gravity
Generalized from the so-called teleparallel gravity which is exactly
equivalent to general relativity, the gravity has been proposed as an
alternative gravity model to account for the dark energy phenomena. In this
letter we prove that the external vacuum gravitational field for a spherically
symmetric distribution of source matter in the gravity framework must be
static and the conclusion is independent of the radial distribution and
spherically symmetric motion of the source matter that is, whether it is in
motion or static. As a consequence, the Birkhoff's theorem is valid in the
general theory. We also discuss its application in the de Sitter
space-time evolution phase as preferred to by the nowadays dark energy
observations.Comment: 5p
Conceptual Unification of Gravity and Quanta
We present a model unifying general relativity and quantum mechanics. The
model is based on the (noncommutative) algebra \mbox{{\cal A}} on the groupoid
\Gamma = E \times G where E is the total space of the frame bundle over
spacetime, and G the Lorentz group. The differential geometry, based on
derivations of \mbox{{\cal A}}, is constructed. The eigenvalue equation for the
Einstein operator plays the role of the generalized Einstein's equation. The
algebra \mbox{{\cal A}}, when suitably represented in a bundle of Hilbert
spaces, is a von Neumann algebra \mathcal{M} of random operators representing
the quantum sector of the model. The Tomita-Takesaki theorem allows us to
define the dynamics of random operators which depends on the state \phi . The
same state defines the noncommutative probability measure (in the sense of
Voiculescu's free probability theory). Moreover, the state \phi satisfies the
Kubo-Martin-Schwinger (KMS) condition, and can be interpreted as describing a
generalized equilibrium state. By suitably averaging elements of the algebra
\mbox{{\cal A}}, one recovers the standard geometry of spacetime. We show that
any act of measurement, performed at a given spacetime point, makes the model
to collapse to the standard quantum mechanics (on the group G). As an example
we compute the noncommutative version of the closed Friedman world model.
Generalized eigenvalues of the Einstein operator produce the correct components
of the energy-momentum tensor. Dynamics of random operators does not ``feel''
singularities.Comment: 28 LaTex pages. Substantially enlarged version. Improved definition
of generalized Einstein's field equation
‘It’s Kinda Punishment’: Tandem Logics and Penultimate Power in the Penal Voluntary Sector for Canadian Youth
This paper draws on original empirical research in Ontario, Canada which analyses penal voluntary sector practice with youth in conflict with the law. I illustrate how youth penal voluntary sector practice (YPVS) operates alongside, or in tandem with the statutory criminal justice system. I argue that examining the PVS and the statutory criminal justice system simultaneously, or in tandem, provides fuller understandings of PVS inclusionary (and exclusionary) control practices (Tomczak and Thompson 2017). I introduce the concept of penultimate power, which demonstrates the ability of PVS workers to trigger criminal justice system response toward a young person in conflict with the law. My novel concepts of tandem logics and penultimate power are useful for understanding PVS practice, explaining how seemingly contradictory approaches across state and ‘community’ organizations not only co-exist, but depend upon the tandem relationship between the PVS and the statutory criminal justice system
Olber's Paradox for Superluminal Neutrinos: Constraining Extreme Neutrino Speeds at TeV-ZeV Energies with the Diffuse Neutrino Background
The only invariant speed in special relativity is c; therefore, if some
neutrinos travel at even tiny speeds above c, normal special relativity is
incomplete and any superluminal speed may be possible. I derive a limit on
superluminal neutrino speeds v >> c at high energies by noting that such speeds
would increase the size of the neutrino horizon. The increased volume of the
Universe visible leads to a brighter astrophysical neutrino background. The
nondetection of "guaranteed" neutrino backgrounds from star-forming galaxies
and ultrahigh energy cosmic rays (UHECRs) constrains v/c at TeV--ZeV energies.
I find that v/c <= 820 at 60 TeV from the nondetection of neutrinos from
star-forming galaxies. The nondetection of neutrinos from UHECRs constrains v/c
to be less than 2500 at 0.1 EeV in a pessimistic model and less than 4.6 at 4
EeV in an optimistic model. The UHECR neutrino background nondetection is
strongly inconsistent with a naive quadratic extrapolation of the OPERA results
to EeV energies. The limits apply subject to some caveats, particularly that
the expected pionic neutrino backgrounds exist and that neutrinos travel faster
than c when they pass the detector. They could be improved substantially as the
expected neutrino backgrounds are better understood and with new experimental
neutrino background limits. I also point out that extremely subluminal speeds
would result in a much smaller neutrino background intensity than expected.Comment: 13 pages, 2 figures, fixed titl
The Sudbury Neutrino Observatory
The Sudbury Neutrino Observatory is a second generation water Cherenkov
detector designed to determine whether the currently observed solar neutrino
deficit is a result of neutrino oscillations. The detector is unique in its use
of D2O as a detection medium, permitting it to make a solar model-independent
test of the neutrino oscillation hypothesis by comparison of the charged- and
neutral-current interaction rates. In this paper the physical properties,
construction, and preliminary operation of the Sudbury Neutrino Observatory are
described. Data and predicted operating parameters are provided whenever
possible.Comment: 58 pages, 12 figures, submitted to Nucl. Inst. Meth. Uses elsart and
epsf style files. For additional information about SNO see
http://www.sno.phy.queensu.ca . This version has some new reference
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