3,387 research outputs found
Observers and Measurements in Noncommutative Spacetimes
We propose a "Copenhagen interpretation" for spacetime noncommutativity. The
goal is to be able to predict results of simple experiments involving signal
propagation directly from commutation relations. A model predicting an energy
dependence of the speed of photons of the order E/E_Planck is discussed in
detail. Such effects can be detectable by the GLAST telescope, to be launched
in 2006.Comment: 10 pp; v2: equivalence of observers explicitely stated; v3: minor
changes, references and remarks added, burst spreading with energy emphasized
as a signature rather than nois
The Mass of the Neutrinos
In the theory of the Dirac equation and in the standard model, the neutrino
is massless. Both these theories use Lorentz invariance. In modern approaches
however, spacetime is no longer smooth, and this modifies special relativity.
We show how such a modification throws up the mass of the (electron) neutrino.Comment: 14 pages, late
On the IR/UV mixing and experimental limits on the parameters of canonical noncommutative spacetimes
We investigate some issues that are relevant for the derivation of
experimental limits on the parameters of canonical noncommutative spacetimes.
By analyzing a simple Wess-Zumino-type model in canonical noncommutative
spacetime with soft supersymmetry breaking we explore the implications of
ultraviolet supersymmetry on low-energy phenomenology. The fact that new
physics in the ultraviolet can modify low-energy predictions affects
significantly the derivation of limits on the noncommutativity parameters based
on low-energy data. These are, in an appropriate sense here discussed,
``conditional limits''. We also find that some standard techniques for an
effective low-energy description of theories with non-locality at short
distance scales are only applicable in a regime where theories in canonical
noncommutative spacetime lack any predictivity, because of the strong
sensitivity to unknown UV physics. It appears useful to combine high-energy
data, from astrophysics, with the more readily available low-energy data.Comment: 14 page
Gravity in quantum spacetime
The literature on quantum-gravity-inspired scenarios for the quantization of
spacetime has so far focused on particle-physics-like studies. This is partly
justified by the present limitations of our understanding of quantum-gravity
theories, but we here argue that valuable insight can be gained through
semi-heuristic analyses of the implications for gravitational phenomena of some
results obtained in the quantum-spacetime literature. In particular, we show
that the types of description of particle propagation that emerged in certain
quantum-spacetime frameworks have striking implications for gravitational
collapse and for the behaviour of gravity at large distances.Comment: This essay received honorable mention in the Gravity Research
Foundation 2010 Awards for Essays on Gravitatio
A phenomenological description of quantum-gravity-induced space-time noise
I propose a phenomenological description of space-time foam and discuss the
experimental limits that are within reach of forthcoming experiments.Comment: 10 pages, LaTex, 1 figure. Short paper, omitting most technical
details. More detailed analysis was reported in gr-qc/010400
Black hole information, unitarity, and nonlocality
The black hole information paradox apparently indicates the need for a
fundamentally new ingredient in physics. The leading contender is nonlocality.
Possible mechanisms for the nonlocality needed to restore unitarity to black
hole evolution are investigated. Suggestions that such dynamics arises from
ultra-planckian modes in Hawking's derivation are investigated and found not to
be relevant, in a picture using smooth slices spanning the exterior and
interior of the horizon. However, no simultaneous description of modes that
have fallen into the black hole and outgoing Hawking modes can be given without
appearance of a large kinematic invariant, or other dependence on
ultra-planckian physics; a reliable argument for information loss thus has not
been constructed. This suggests that strong gravitational dynamics is
important. Such dynamics has been argued to be fundamentally nonlocal in
extreme situations, such as those required to investigate the fate of
information.Comment: 34 pages, 4 figures. Major revision of hep-th/0604047. v2: minor
corrections and added referenc
Spectral Line Broadening and Angular Blurring due to Spacetime Geometry Fluctuations
We treat two possible phenomenological effects of quantum fluctuations of
spacetime geometry: spectral line broadening and angular blurring of the image
of a distance source. A geometrical construction will be used to express both
effects in terms of the Riemann tensor correlation function. We apply the
resulting expressions to study some explicit examples in which the fluctuations
arise from a bath of gravitons in either a squeezed state or a thermal state.
In the case of a squeezed state, one has two limits of interest: a coherent
state which exhibits classical time variation but no fluctuations, and a
squeezed vacuum state, in which the fluctuations are maximized.Comment: 21 pages, 2 figures. Dedicated to Raphael Sorkin on the occasion of
his 60th birthday. (v2: several references added and some minor errors
corrected
Pengaruh Keragaman Menu, Harga, Dan Citra Merek Terhadap Keputusan Pembelian (Studi Kasus Pada Konsumen Restoran D\u27cost Seafood Semarang)
The increasing number of alternative choice of restaurants in the city of Semarang cause competition getting tougher.As a result, many businesses that compete in the business of restaurants.D\u27cost seafood restaurant is one of the options in the city of Semarang. The number of restaurants that serves a similar menu variety at low prices caused the number of visitors D\u27Cost experience fluctuations from year 2014-2016. This is demonstrated by a decrease in the number of visitors by 2014 to 2015 of 0.2% and by 2015 to 2016 experienced increases of 2%.The purpose of this research is to know the influence of the diversity of the menu, the price and brand image against consumer purchasing decisions D\u27Cost Seafood. This research type is explanatory research. Sampling techniques using a purposive Sampling method.As for the number of samples taken as many as 100 respondents. Data were analyzed through the test validity, reliability test, correlation coefficient, crosstab, determination of the coefficient of linear regression, simple, multiple linear regression, t-test, F-test, and with the help of the program SPSS.Based on the results of the descriptive analysis, showed the results of research that the diversity of the menu are on various categories of 59.0 percent. Variable rates are at a sufficient category, amounting to 48.0 percent. Brand image is variable in quality, category of 74.0 percent and the variable purchase decisions are high on the category, for 57.0 percent. Multiple correlation coefficient calculation based on yield value of 0.695 which means to have a strong correlation. Based on the calculation of the coefficient of determination indicates that the variable is the diversity of the menu, prices, and brand image contributed to the influence of 48.3 per cent against a purchasing decision.Suggestion in this research areproviding new menu variations according to the wishes of consumers. Improve the quality of the product and provide cheap package price promotions are also very necessary. In addition, the necessity of observing the tagline of which belonged to the "Mutu Bintang Lima Harga Kaki Lima" because according to the perceptions of the respondents, the tagline does not correspond to reality
Planck-scale deformation of Lorentz symmetry as a solution to the UHECR and the TeV- paradoxes
One of the most puzzling current experimental physics paradoxes is the
arrival on Earth of Ultra High Energy Cosmic Rays with energies above the GZK
threshold. The recent observation of 20TeV photons from Mk 501 is another
somewhat similar paradox. Several models have been proposed for the UHECR
paradox. No solution has yet been proposed for the TeV- paradox.
Remarkably, the drastic assumption of a violation of ordinary Lorentz
invariance would resolve both paradoxes. We present a formalism for the
description of the type of Lorentz-invariance deformation (LID) that could be
induced by non-trivial short-distance structure of space-time, and we show that
this formalism is well suited for comparison of experimental data with LID
predictions. We use the UHECR and TeV- data, as well as bounds on
time-of-flight differences between photons of different energies, to constrain
the LID parameter space. A model with only two parameters, an energy scale and
a dimensionless parameter characterizing the functional dependence on the
energy scale, is shown to be sufficient to solve both the UHECR and the
TeV- threshold anomalies while satisfying the time-of-flight bounds.
The allowed region of the two-parameter space is relatively small, but,
remarkably, it fits perfectly the expectations of the quantum-gravity-motivated
space-time models known to support such deformations of Lorentz invariance:
integer value of the dimensionless parameter and characteristic energy scale
constrained to a narrow interval in the neighborhood of the Planck scale.Comment: LaTex (epsfig), 20 pages, 3 figure
Massive Gauge Fields and the Planck Scale
The present work is devoted to massive gauge fields in special relativity
with two fundamental constants-the velocity of light, and the Planck length, so
called doubly special relativity (DSR). The two invariant scales are accounted
for by properly modified boost parameters. Within above framework we construct
the vector potential as the (1/2,0)x(0,1/2) direct product, build the
associated field strength tensor together with the Dirac spinors and use them
to calculate various observables as functions of the Planck length.Comment: Affiliation of first author updated; Reference [13] updated; Typos in
Refs. [15], [19] correcte
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