1,848 research outputs found
Is violation of Newton's second law possible?
Astrophysical observations (usually explained by dark matter) suggest that
classical mechanics could break down when the acceleration becomes extremely
small (the approach known as modified Newtonian dynamics, or MOND). I present
the first analysis of MOND manifestations in terrestrial (rather than
astrophysical) settings. A new effect is reported: around each equinox date, 2
spots emerge on the Earth where static bodies experience spontaneous
acceleration due to the possible violation of Newton's second law. Preliminary
estimates indicate that an experimental search for this effect can be feasible.Comment: 10 pages; minor changes to match the published versio
Quantum correlations and Nash equilibria of a bi-matrix game
Playing a symmetric bi-matrix game is usually physically implemented by
sharing pairs of 'objects' between two players. A new setting is proposed that
explicitly shows effects of quantum correlations between the pairs on the
structure of payoff relations and the 'solutions' of the game. The setting
allows a re-expression of the game such that the players play the classical
game when their moves are performed on pairs of objects having correlations
that satisfy the Bell's inequalities. If players receive pairs having quantum
correlations the resulting game cannot be considered another classical
symmetric bi-matrix game. Also the Nash equilibria of the game are found to be
decided by the nature of the correlations.Comment: minor correction
Quantized Casimir Force
We investigate the Casimir effect between two-dimensional electron systems
driven to the quantum Hall regime by a strong perpendicular magnetic field. In
the large separation (d) limit where retardation effects are essential we find
i) that the Casimir force is quantized in units of 3\hbar c \alpha^2/(8\pi^2
d^4), and ii) that the force is repulsive for mirrors with same type of
carrier, and attractive for mirrors with opposite types of carrier. The sign of
the Casimir force is therefore electrically tunable in ambipolar materials like
graphene. The Casimir force is suppressed when one mirror is a charge-neutral
graphene system in a filling factor \nu=0 quantum Hall state.Comment: 4.2 page
Towards the use of the most massive black hole candidates in AGN to test the Kerr paradigm
The super-massive objects in galactic nuclei are thought to be the Kerr black
holes predicted by General Relativity, although a definite proof of their
actual nature is still lacking. The most massive objects in AGN () seem to have a high radiative efficiency () and a
moderate mass accretion rate (). The high
radiative efficiency could suggest they are very rapidly-rotating black holes.
The moderate luminosity could indicate that their accretion disk is
geometrically thin. If so, these objects could be excellent candidates to test
the Kerr black hole hypothesis. An accurate measurement of the radiative
efficiency of an individual AGN may probe the geometry of the space-time around
the black hole candidate with a precision comparable to the one achievable with
future space-based gravitational-wave detectors like LISA. A robust evidence of
the existence of a black hole candidate with and accreting from a
thin disk may be interpreted as an indication of new physics. For the time
being, there are several issues to address before using AGN to test the Kerr
paradigm, but the approach seems to be promising and capable of providing
interesting results before the advent of gravitational wave astronomy.Comment: 12 pages, 6 figures. v2: some typos correcte
Tests of new physics from precise measurements of the Casimir pressure between two gold-coated plates
A micromechanical torsion oscillator has been used to strengthen the limits
on new Yukawa forces by determining the Casimir pressure between two
gold-coated plates. By significantly reducing the random errors and obtaining
the electronic parameters of the gold coatings, we were able to conclusively
exclude the predictions of large thermal effects below 1 m and strengthen
the constraints on Yukawa corrections to Newtonian gravity in the interaction
range from 29.5 nm to 86 nm.Comment: 8 pages, 3 figures, to appear in Phys. Rev.
New two-sided bound on the isotropic Lorentz-violating parameter of modified Maxwell theory
There is a unique Lorentz-violating modification of the Maxwell theory of
photons, which maintains gauge invariance, CPT, and renormalizability.
Restricting the modified-Maxwell theory to the isotropic sector and adding a
standard spin-one-half Dirac particle p^\pm with minimal coupling to the
nonstandard photon \widetilde{\gamma}, the resulting
modified-quantum-electrodynamics model involves a single dimensionless
"deformation parameter," \widetilde{\kappa}_{tr}. The exact tree-level decay
rates for two processes have been calculated: vacuum Cherenkov radiation p^\pm
\to p^\pm \widetilde{\gamma} for the case of positive \widetilde{\kappa}_{tr}
and photon decay \widetilde{\gamma} \to p^+ p^- for the case of negative
\widetilde{\kappa}_{tr}. From the inferred absence of these decays for a
particular high-quality ultrahigh-energy-cosmic-ray event detected at the
Pierre Auger Observatory and an excess of TeV gamma-ray events observed by the
High Energy Stereoscopic System telescopes, a two-sided bound on
\widetilde{\kappa}_{tr} is obtained, which improves by eight orders of
magnitude upon the best direct laboratory bound. The implications of this
result are briefly discussed.Comment: 18 pages, v5: published version in preprint styl
Probing long-range leptonic forces with solar and reactor neutrinos
In this work we study the phenomenological consequences of the existence of
long-range forces coupled to lepton flavour numbers in solar neutrino
oscillations. We study electronic forces mediated by scalar, vector or tensor
neutral bosons and analyze their effect on the propagation of solar neutrinos
as a function of the force strength and range. Under the assumption of one mass
scale dominance, we perform a global analysis of solar and KamLAND neutrino
data which depends on the two standard oscillation parameters, \Delta m^2_{21}
and \tan^2\theta_{12}, the force coupling constant, its range and, for the case
of scalar-mediated interactions, on the neutrino mass scale as well. We find
that, generically, the inclusion of the new interaction does not lead to a very
statistically significant improvement on the description of the data in the
most favored MSW LMA (or LMA-I) region. It does, however, substantially improve
the fit in the high-\Delta m^2 LMA (or LMA-II) region which can be allowed for
vector and scalar lepto-forces (in this last case if neutrinos are very
hierarchical) at 2.5\sigma. Conversely, the analysis allows us to place
stringent constraints on the strength versus range of the leptonic interaction.Comment: 20 pages, 8 figure
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