370 research outputs found
Transitions between levels of a quantum bouncer induced by a noise-like perturbation
The probability of transition between levels of a quantum bouncer, induced by
a noise-like perturbation, is calculated. The results are applied to two
sources of noise (vibrations and mirror surface waviness) which might play an
important role in future GRANIT experiment, aiming at precision studies of/with
the neutron quantum bouncer
Constraints on spin-dependent short-range interactions using gravitational quantum levels of ultracold neutrons
In this paper, we discuss a possibility to improve constraints on
spin-dependent short-range interactions in the range of 1 - 200 micrometer
significantly. For such interactions, our constraints are without competition
at the moment. They were obtained through the observation of gravitationally
bound states of ultracold neutrons. We are going to improve these constraints
by about three orders of magnitude in a dedicated experiment with polarized
neutrons using the next-generation spectrometer GRANIT.Comment: 5 pages, 4 figures, accepted for publication in the Proceedings of
the International Workshop on Particle Physics with Cold Neutrons, Grenoble,
May 2008, to be published in Nucl. Instr. and Meth.
The reflection of very cold neutrons from diamond powder nanoparticles
We study possibility of efficient reflection of very cold neutrons (VCN) from
powders of nanoparticles. In particular, we measured the scattering of VCN at a
powder of diamond nanoparticles as a function of powder sample thickness,
neutron velocity and scattering angle. We observed extremely intense scattering
of VCN even off thin powder samples. This agrees qualitatively with the model
of independent nanoparticles at rest. We show that this intense scattering
would allow us to use nanoparticle powders very efficiently as the very first
reflectors for neutrons with energies within a complete VCN range up to
eV
A quantum mechanical description of the experiment on the observation of gravitationally bound states
Quantum states in the Earth's gravitational field were observed, when
ultra-cold neutrons fall under gravity. The experimental results can be
described by the quantum mechanical scattering model as it is presented here.
We also discuss other geometries of the experimental setup which correspond to
the absence or the reversion of gravity. Since our quantum mechanical model
describes, particularly, the experimentally realized situation of reversed
gravity quantitatively, we can practically rule out alternative explanations of
the quantum states in terms of pure confinement effects.Comment: LaTeX, 10 pages, 4 figures, v2: references adde
On gravity as an entropic force
We consider E. Verlinde's proposal that gravity is an entropic force -- we
shall call this theory entropic gravity (EG) -- and reanalyze a recent claim
that this theory is in contradiction with the observation of the
gravitationally-bound ground state of neutrons in the GRANIT experiment. We
find that EG does not necessarily contradict the existence of
gravitationally-bound quantum states of neutrons in the Earth's gravitational
field, since EG is equivalent to Newtonian gravity in this case. However,
certain transitions between the gravitationally-bound quantum states of
neutrons, in particular spontaneous decays of excited states, which can
hopefully be observed in future experiments, cannot be explained in the
framework of EG, unless essential ingredients are introduced into it.
Otherwise, a quantized description of gravity will be required.Comment: 6 pages, v2: the possibility that graviton may appear as an emergent
concept in EG is noted, few improvements in arguments and presentation, some
typos and grammar corrected. To appear in Phys. Lett.
Quantum and Classical divide: the gravitational case
We study the transition between quantum and classical behavior of particles
in a gravitational quantum well. We analyze how an increase in the particles
mass turns the energy spectrum into a continuous one, from an experimental
point of view. We also discuss the way these effects could be tested by
conducting experiments with atoms and fullerene-type molecules.Comment: Revtex4, 5 pages, 2 figures; version to appear in Physics Letters
Main effects of the Earth's rotation on the stationary states of ultra-cold neutrons
The relativistic corrections in the Hamiltonian for a particle in a uniformly
rotating frame are discussed. They are shown to be negligible in the case of
ultra-cold neutrons (UCN) in the Earth's gravity. The effect, on the energy
levels of UCN, of the main term due to the Earth's rotation, i.e. the
angular-momentum term, is calculated. The energy shift is found proportional to
the energy level itself.Comment: 12 pages in standard LaTeX. v3: Former sect. 2 (derivation of the
non-relativistic Hamiltonian) suppressed, new refs., interpretation of the
energy shift added, and new redactional improvements, to meet the editorial
demands. To appear in Physics Letters
Nanoparticles as a possible moderator for an ultracold neutron source
Ultracold and very cold neutrons (UCN and VCN) interact strongly with
nanoparticles due to the similarity of their wavelengths and nanoparticles
sizes. We analyze the hypothesis that this interaction can provide efficient
cooling of neutrons by ultracold nanoparticles at certain experimental
conditions, thus increasing the density of UCN by many orders of magnitude. The
present analytical and numerical description of the problem is limited to the
model of independent nanoparticles at zero temperature. Constraints of
application of this model are discussed
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