1,720,995 research outputs found
Self-interacting complex scalar field as dark matter
No full textWe study the viability of a a complex scalar field χ with self-interacting potential V=m0χ/2|χ| 2+h|χ|4 as dark matter. Due to the self interaction, the scalar field forms a Bose-Einstein condensate at early times that represents dark matter. The self interaction is also responsible of quantum corrections to the scalar field mass that naturally give the dark matter domination at late times without any fine tuning on the energy density of the scalar field at early times. Finally the properties of the spherically symmetric dark matter halos are also discussed. © 2011 American Institute of Physics
Trapped Bose-Einstein condensates with Planck-scale induced deformation of the energy-momentum dispersion relation
No full textWe show that harmonically trapped Bose-Einstein condensates can be used to constrain Planck-scale physics. In particular we prove that a Planck-scale induced deformation of the Minkowski energy-momentum dispersion relation δE≃ξ 1mcp/2M p produces a shift in the condensation temperature T c of about δTc/Tc0≃10-6ξ1 for typical laboratory conditions. Such a shift allows to bound the deformation parameter up to |ξ 1|≲10 4. Moreover we show that it is possible to enlarge δTc/Tc0 and improve the bound on ξ 1 lowering the frequency of the harmonic trap. Finally we compare the Planck-scale induced shift in T c with similar effects due to interboson interactions and finite size effects. © 2012 Elsevier B.V
Interaction effects on atomic laboratory trapped Bose-Einstein condensates
No full textWe discuss the effect of inter-atoms interactions on the condensation temperature
Tc of an atomic laboratory trapped
Bose-Einstein condensate. We show that, in the mean-field Hartree-Fock and semiclassical
approximations, interactions produce a shift
ΔTc/Tc0 ≈ b1(a/λTc) + b2(a/λTc)2 + ψ[a / λTc]
with a the s-wave scattering length,
λT the thermal wavelength and
ψ[a / λTc]
a non-analytic function such that
ψ[0] = ψ′[0] = ψ′′[0] = 0 and
|ψ′′′[0]| = ∞. Therefore, with no more assumptions than Hartree-Fock
and semiclassical approximations, interaction effecs are perturbative to second order in
a / λTc
and the expected non-perturbativity of physical quantities at critical temperature appears
only to third order. We compare this finding with different results by other authors,
which are based on more than the Hartree-Fock and semiclassical approximations. Moreover,
we obtain an analytical estimation for b2 ≃ 18.8 which
improves a previous numerical result. We also discuss how the discrepancy between
b2 and the empirical value of
b2 = 46 ± 5 may be explained with no need to resort to
beyond-mean field effects
Collective behavior of light in vacuum
No full textUnder the action of light-by-light scattering, light beams show collective behaviors in vacuum. For instance, in the case of two counterpropagating laser beams with specific initial helicity, the polarization of each beam oscillates periodically between the left and right helicity. Furthermore, the amplitudes and the corresponding intensities of each polarization propagate like waves. Such polarization waves might be observationally accessible in future laser experiments, in a physical regime complementary to those explored by particle accelerators
Light polarization oscillations induced by photon-photon scattering
No full textWe consider the Heisenberg-Euler action for an electromagnetic field in vacuum, which includes quantum corrections to the Maxwell equations induced by photon-photon scattering. We show that, in some configurations, the plane monochromatic waves become unstable, due to the appearance of secularities in the dynamical equations. These secularities can be treated using a multiscale approach, introducing a slow time variable. The amplitudes of the plane electromagnetic waves satisfy a system of ordinary differential nonlinear equations in the slow time. The analysis of this system shows that, due to the effect of photon-photon scattering, in the unstable configurations the electromagnetic waves oscillate periodically between left-hand-sided and right-hand-sided polarizations. Finally, we discuss the physical implications of this finding and the possibility of disclosing traces of this effect in optical experiments
The Schrödinger–Poisson equations as the large-N limit of the Newtonian N-body system: applications to the large scale dark matter dynamics
No full textIn this paper it is argued how the dynamics of the classical Newtonian N-body system can be described in terms of the Schrödinger–Poisson equations in the large N limit. This result is based on the stochastic quantization introduced by Nelson, and on the Calogero conjecture. According to the Calogero conjecture, the emerging effective Planck constant is computed in terms of the parameters of the N-body system as ℏ∼M5/3G1/2(N/⟨ρ⟩)1/6ℏ∼M5/3G1/2(N/⟨ρ⟩)1/6 , where is G the gravitational constant, N and M are the number and the mass of the bodies, and ⟨ρ⟩⟨ρ⟩ is their average density. The relevance of this result in the context of large scale structure formation is discussed. In particular, this finding gives a further argument in support of the validity of the Schrödinger method as numerical double of the N-body simulations of dark matter dynamics at large cosmological scales
Viability of complex self-interacting scalar field as dark matter
No full textWe study the viability of a complex scalar field χ with self-interacting potential V=m0χ/2|χ|2+h|χ|4 as dark matter. The scalar field is produced at reheating through the decay of the inflaton field and then, due to the self-interaction, a Bose-Einstein condensate of χ particles forms. The condensate represents dark matter in that model. We analyze the cosmological evolution of the model, stressing how, due to the presence of the self-interaction, the model naturally admits dark matter domination at late times, thus avoiding any fine tuning on the energy density of the scalar field at early times. Finally we give a lower bound for the size of dark matter halos at present time and we show that our model is compatible with dark matter halos greater than 0.1 kpc and with BBN and CMB bounds on the effective number of extra neutrinos Δνeff. Therefore, the model is viable and for hb≃10-4-10-12 one obtains a mass mχb≃m0χb≃1-10-2 eV for dark matter particles from radiation-matter equality epoch to present time, but at temperatures Tγ≫10 eV, where Tγ is the photons temperature, thermal corrections to m0χ due to the self-coupling h are dominant. © 2011 Elsevier B.V
Unattainability of the trans-Planckian regime in nonlocal quantum gravity
Full text linkBased on the ultraviolet asymptotic freedom of nonlocal quantum gravity, we show that the trans-Planckian energy regime is unattainable in laboratory experiments. As physical implications, it turns out that the violation of causality, typical of nonlocal field theories, can never be detected in particle accelerators, while the asymptotic freedom of the theory provides an elegant solution to the so called trans-Planckian cosmological problem
Condensation temperature of strongly interacting 39K condensates in the mean-field and semi-classical approximations
No full textWe consider the effect of inter-atom interactions on the condensation temperature Tc of an atomic Bose-Einstein condensate. We find an analytic expression of the shift in Tc induced by interactions with respect the ideal non-interacting case, in the mean-field and semi-classical approximations. Such a shift is expressed in terms of the ratio a/lambda Tc between the s-wave scattering length a and the thermal wavelength lambda Tc. This result is used to discuss the tension between mean-field predictions and observations in strongly interacting 39K condensates. It is shown that such a tension is solved taking into account the details of the Feshbach resonance used to tune a in the experiments.(c) 2022 Elsevier B.V. All rights reserved
Isochronous Spacetimes
No full textThe possibility has been recently demonstrated to manufacture
(nonrelativistic, Hamiltonian) many-body problems which feature an \textit{%
isochronous} time evolution with an arbitrarily assigned period
yet mimic with good approximation, or even exactly, any given
many-body problem (within a quite large class, encompassing most
of nonrelativistic physics) over times which may also
be arbitrarily large (but of course such that ). In
this paper we review and further explore the possibility to extend
this finding to a general relativity context, so that it becomes
relevant for cosmology
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