1,128 research outputs found
High contrast D line electromagnetically induced transparency in nanometric-thin rubidium vapor cell
Electromagnetically induced transparency (EIT) on atomic D line of
rubidium is studied using a nanometric-thin cell with atomic vapor column
length in the range of L= 400 - 800 nm. It is shown that the reduction of the
cell thickness by 4 orders as compared with an ordinary cm-size cell still
allows to form an EIT resonance for ( nm) with the
contrast of up to 40%. Remarkable distinctions of EIT formation in
nanometric-thin and ordinary cells are demonstrated. Despite the Dicke effect
of strong spectral narrowing and increase of the absorption for , EIT resonance is observed both in the absorption and the fluorescence
spectra for relatively low intensity of the coupling laser. Well resolved
splitting of the EIT resonance in moderate magnetic field for
can be used for magnetometry with nanometric spatial resolution. The presented
theoretical model well describes the observed results.Comment: Submitted to Applied Physics B: Lasers and Optics, 9 pages, 10
figure
Erratum (astro-ph/0510172): Robust Limits on Lorentz Violation from Gamma-Ray Bursts
We correct the fitting formula used in refs. [1,2] to obtain a robust limit
on a violation of Lorentz invariance that depends linearly on the photon
energy. The correction leads to a slight increase of the limit on the scale of
the violation, to M > 1.4 x 10^{16} GeV.Comment: four pages latex, two eps figures, uses special macro
Lorentz Invariance Violation induced time delays in GRBs in different cosmological models
Lorentz Invariance Violation (LIV) manifesting itself by energy dependent
modification of standard relativistic dispersion relation has recently
attracted a considerable attention. Ellis et al. previously investigated the
energy dependent time offsets in different energy bands on a sample of gamma
ray bursts and, assuming standard cosmological model, they found a weak
indication for redshift dependence of time delays suggestive of LIV. Going
beyond the CDM cosmology we extend this analysis considering also four
alternative models of dark energy (quintessence with constant and variable
equation of state, Chaplygin gas and brane-world cosmology). It turns out that
the effect noticed by Ellis et al. is also present in those models and is the
strongest for quintessence with variable equation of state.Comment: 14 pages, 1 figur
GRB 051221A and Tests of Lorentz Symmetry
Various approaches to quantum gravity suggest the possibility of violation of
Lorentz symmetry at very high energies. In these cases we expect a modification
at low energies of the dispersion relation of photons that contains extra
powers of the momentum suppressed by a high energy scale. These terms break
boost invariance and can be tested even at relatively low energies. We use the
light curves of the very bright short Gamma-Ray Burst GRB 051221A and compare
the arrival times of photons at different energies with the expected time delay
due to a modified dispersion relation. As no time delay was observed, we set a
lower bound of 0.0066 E_{pl} \sim 0.66 10^{17} GeV on the scale of Lorentz
invariance violation.Comment: 9 pages, 2 figure
Photon mass limits from fast radio bursts
International audienceThe frequency-dependent time delays in fast radio bursts (FRBs) can be used to constrain the photon mass, if the FRB redshifts are known, but the similarity between the frequency dependences of dispersion due to plasma effects and a photon mass complicates the derivation of a limit on mÎł. The dispersion measure (DM) of FRB 150418 is known to âŒ0.1%, and there is a claim to have measured its redshift with an accuracy of âŒ2%, but the strength of the constraint on mÎł is limited by uncertainties in the modelling of the host galaxy and the Milky Way, as well as possible inhomogeneities in the intergalactic medium (IGM). Allowing for these uncertainties, the recent data on FRB 150418 indicate that mÎłâČ1.8Ă10â14 eVcâ2 (3.2Ă10â50 kg), if FRB 150418 indeed has a redshift z=0.492 as initially reported. In the future, the different redshift dependences of the plasma and photon mass contributions to DM can be used to improve the sensitivity to mÎł if more FRB redshifts are measured. For a fixed fractional uncertainty in the extra-galactic contribution to the DM of an FRB, one with a lower redshift would provide greater sensitivity to mÎł
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A review of the role of the Atlantic meridional overturning circulation in Atlantic multidecadal variability and associated climate impacts
By synthesizing recent studies employing a wide range of approaches (modern observations, paleo reconstructions, and climate model simulations), this paper provides a comprehensive review of the linkage between multidecadal Atlantic Meridional Overturning Circulation (AMOC) variability and Atlantic Multidecadal Variability (AMV) and associated climate impacts. There is strong observational and modeling evidence that multidecadal AMOC variability is a crucial driver of the observed AMV and associated climate impacts and an important source of enhanced decadal predictability and prediction skill. The AMOCâAMV linkage is consistent with observed key elements of AMV. Furthermore, this synthesis also points to a leading role of the AMOC in a range of AMVârelated climate phenomena having enormous societal and economic implications, for example, Intertropical Convergence Zone shifts; Sahel and Indian monsoons; Atlantic hurricanes; El NiñoâSouthern Oscillation; Pacific Decadal Variability; North Atlantic Oscillation; climate over Europe, North America, and Asia; Arctic sea ice and surface air temperature; and hemisphericâscale surface temperature. Paleoclimate evidence indicates that a similar linkage between multidecadal AMOC variability and AMV and many associated climate impacts may also have existed in the preindustrial era, that AMV has enhanced multidecadal power significantly above a red noise background, and that AMV is not primarily driven by external forcing. The role of the AMOC in AMV and associated climate impacts has been underestimated in most stateâofâtheâart climate models, posing significant challenges but also great opportunities for substantial future improvements in understanding and predicting AMV and associated climate impacts
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