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Casimir forces and non-Newtonian gravitation
Full text linkThe search for non-relativistic deviations from Newtonian gravitation can lead to new phenomena signalling the unification of gravity with the other fundamental interactions. Various recent theoretical frameworks indicate a possible window for non-Newtonian forces with gravitational coupling strength in the micrometre range. The major expected background in the same range is attributable to the Casimir force or variants of it if dielectric materials, rather than conducting ones, are considered. Here we review the measurements of the Casimir force performed so far in the micrometre range and how they determine constraints on non-Newtonian gravitation, also discussing the dominant sources of false signals. We also propose a geometry-independent parameterization of all data in terms of the measurement of the constant (h) over barc. Any Casimir force measurement should lead, once all corrections are taken into account, to a determination of the constant (h) over barc which, in order to assess the accuracy of the measurement, can be compared with its more precise value known through microscopic measurements. Although the last decade of experiments has resulted in solid demonstrations of the Casimir force, the situation is not conclusive with respect to being able to discover new physics. Future experiments and novel phenomenological analysis will be necessary to discover non-Newtonian forces or to push the window for their possible existence into regions of the parameter space which theoretically appear unnatural
QUANTUM NONDEMOLITION OBSERVABLES FOR A WEBER-TYPE GRAVITATIONAL-WAVE ANTENNA COUPLED TO A RESONANT TRANSDUCER
No full textWe present a general proof of the QND nature of the complex amplitudes for two coupled harmonic oscillators. The possibilities of the QND schemes for the detection of gravitational waves with a Weber-type antenna coupled to a resonant transducer are discussed, as well as their importance for the design of the next generation of gravitational wave antennas
ON WEAK INTERACTIONS AS SHORT-DISTANCE MANIFESTATIONS OF GRAVITY
No full textWe conjecture that weak interactions are peculiar manifestations of quantum gravity at the Fermi scale, and that the Fermi constant is related to the Newtonian constant of gravitation. In this framework one may understand the violations of fundamental symmetries by the weak interactions, in particular parity violations, as due to fluctuations of the spacetime geometry at a Planck scale coinciding with the Fermi scale. As a consequence, gravitational phenomena should play a more important role in the microworld, and experimental settings are suggested to test this hypothesis
QUANTUM NONDEMOLITION STROBOSCOPIC OBSERVABLES AND MULTIPUMPING BACK-ACTION EVASION SCHEMES
No full textIt is shown that quantum non-demolition stroboscopic measurements of a complex amplitude of a harmonic oscillator are obtained as a limit of a multipump back-action evasion scheme. As a consequence of the analogy between these two strategies a new stroboscopic scheme for the detection of small displacements in macroscopic mechanical oscillators is proposed
Neutrino mass variability due to nonminimal coupling to spacetime curvature in neutrinophilic two-Higgs-doublet models
No full textIn neutrinophilic two-Higgs-doublet models, neutrinos acquire mass due to a Higgs field with vacuum expectation value of the order of ’ 102 eV, corresponding to a Compton wavelength in the 10 m range. This creates a situation in which nonminimal couplings between Higgs fields and spacetime curvature may lead to novel observable effects. Among these, we discuss the possibility of variable neutrino masses, with implications for the dependence of the neutrino oscillation frequency on the spacetime curvature, a further source of dispersion of the neutrino arrival times from supernovae events, and possibly also a mechanism leading to gravitationally-induced neutrino superluminality. Finally, we propose laboratoryscale experiments in which properly designed electroweak cavities may be used to change neutrino masses, which should be observable through time of flight experiments
ARE QUANTUM MEASUREMENTS ON MACROSCOPIC BODIES FEASIBLE
No full textThe possibility to test quantum measurement theories is discussed in the more phenomenological framework of the quantum nondemolition theory. A simple test of the hypothesis of the state vector collapse is proposed by looking for deviations from the Boltzmann distribution of the energy associated to only one complex amplitude of a macroscopic oscillator
Is the law of universal gravitation valid at short distances?
No full textRecently, short-range macroscopic forces superimposed to gravity have been conjectured. We argue that their existence is unavoidable if gravity has to be merged with the other fundamental interactions within the currently accepted paradigms for unification. A first attempt to detect such forces in the macroscopic range using micromechanical resonators is reported, together with a discussion of further sensitivity improvements. Implications of the possible discovery of these new interactions in elementary particle physics and cosmology are outlined
Recent experiments in Bose-Einstein condensation: Superradiance and critical velocities
No full textWorkshop at University of Maryland, Baltimore
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