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Electro-thermal coupling in semiconductor bolometers is known to create nonlinearities in transient detector response, particularly when such detectors are biased outside of their ideal regions (i.e. past the turnover point in their IV curves). This effect is further compounded in the case where a stray capacitance in the bias circuit is present, for example in long cryogenic cabling. We present a physical model of the influence of such electro-thermal coupling and stray capacitance in a composite NTD germanium bolometer, in which previous experimental data at high V bias resulted in oscillations of the impulse response of the detector to irradiation by alpha particles. The model reproduces the transient oscillations seen in the experimental data, depending both on electro-thermal coupling and stray capacitance. This is intended as an experimental and simulated example of such oscillations, demonstrated for the specific case of this bolometric detector.

H.A. Wilson, then R.H. Dicke, proposed to describe gravitation by a spatial change of the refractive index of the vacuum around a gravitational mass. Dicke extended this formalism in order to describe the apparent expansion of the universe by a cosmological time dependence of the global vacuum index. In this paper, we develop Dicke’s formalism. The metric expansion in standard cosmology (the time-dependent scale factor of the Friedmann–Lemaître curved spacetime metric) is replaced by a flat and static Euclidean metric with a change with time of the vacuum index. We show that a vacuum index increasing with time produces both the cosmological redshift and time dilation, and that the predicted evolution of the energy density of the cosmological microwave background is consistent with the standard cosmology. We then show that the type Ia supernovæ data, from the joint SDSS-II and SNLS SNe-Ia samples, are well modeled by a vacuum index varying exponentially as n(t)=exp(t/τ0), where τ0=8.0-0.8+0.2 Gyr. The main consequence of this formalism is that the cosmological redshift should affect any atom, with a relative decrease of the energy levels of about -210-18s-1. Possibilities for an experimental investigation of this prediction are discussed.

We introduce the ‘Joule stepping’ technique, whereupon a constantly biased bolometer has its bias voltage modified by a small additional step. We demonstrate this technique using a composite NTD semiconductor bolometer and a pulsing device that sends an extra step in voltage. We demonstrate the results of the technique over a range of bias voltages at 100, 200 and 300 mK. Joule stepping allows us to directly measure long thermal tails with low amplitudes in the response of the global thermal architecture of bolometers and could be a useful tool to quickly and easily calibrate the thermal time response of individual bolometric detectors or channels. We also show that the derivative of the Joule step is equivalent to the bolometer response to a δ -pulse (or Joule pulse), which allows for greater understanding of transient behaviour with a better signal-to-noise ratio than pulsing alone can provide. Finally, we compare Joule step pulses with pulses produced by α particles, finding a good agreement between their fast decay constants, but a discrepancy between their thermal decay constants.

It is proved that EJE_J is injective if EE is an injective module over a valuation ring RR, for each prime ideal J≠ZJ\\ne Z. Moreover, if EE or ZZ is flat, then EZE_Z is injective, too. It follows that localizations of injective modules over h-local Prüfer domains are injective, too.

H.A. Wilson, then R.H. Dicke, proposed to describe gravitation by a spatial change of the refractive index of the vacuum around a gravitational mass. Dicke extended this formalism in order to describe the apparent expansion of the Universe by a cosmological time dependence of the global vacuum index. In this paper, we develop Dicke's formalism. The metric expansion in standard cosmology (the time-dependent scale factor of the Friedmann-Lemaître curved spacetime metric) is replaced by a flat and static Euclidean metric with a change with time of the vacuum index. We show that a vacuum index increasing with time produces both the cosmological redshift and time dilation, and that the predicted evolution of the energy density of the cosmological microwave background is consistent with the standard cosmology. We then show that the type Ia supernovae data, from the joint SDSS-II and SNLS SNe-Ia samples, are well modeled by a vacuum index varying exponentially as n(t)=exp(t/tau0), where tau0=8.0+0.2-0.8 Gyr. The main consequence of this formalism is that the cosmological redshift should affect any atom, with a relative decrease of the energy levels of about -2 10^{-18} per second. Possibilities for an experimental investigation of this prediction are discussed.

When combining cosmological and oscillations results to constrain the neutrino sector, the question of the propagation of systematic uncertainties is often raised. We address this issue in the context of the derivation of an upper bound on the sum of the neutrino masses (\\(\\Sigma m_\\nu\\)) with recent cosmological data. This work is performed within the \\({{\\mathrm{\\Lambda{CDM}}}\\) model extended to \\(\\Sigma m_\\nu\\), for which we advocate the use of three mass-degenerate neutrinos. We focus on the study of systematic uncertainties linked to the foregrounds modelling in CMB data analysis, and on the impact of the present knowledge of the reionisation optical depth. This is done through the use of different likelihoods built from Planck data. Limits on \\(\\Sigma m_\\nu\\) are derived with various combinations of data, including the latest Baryon Acoustic Oscillations (BAO) and Type Ia Supernovae (SN) results. We also discuss the impact of the preference for current CMB data for amplitudes of the gravitational lensing distortions higher than expected within the \\({{\\mathrm{\\Lambda{CDM}}}\\) model, and add the Planck CMB lensing. We then derive a robust upper limit: \\(\\Sigma m_\\nu< 0.17\\hbox{ eV at }95\\% \\hbox{CL}\\), including 0.01 eV of foreground systematics. We also discuss the neutrino mass repartition and show that today's data do not allow one to disentangle normal from inverted hierarchy. The impact on the other cosmological parameters is also reported, for different assumptions on the neutrino mass repartition, and different high and low multipole CMB likelihoods.

We demonstrate that the cosmic microwave background (CMB) temperature-polarization cross-correlation provides accurate and robust constraints on cosmological parameters. We compare them with the results from temperature or polarization and investigate the impact of foregrounds, cosmic variance, and instrumental noise. This analysis makes use of the Planck high-multipole HiLLiPOP likelihood based on angular power spectra, which takes into account systematics from the instrument and foreground residuals directly modelled using Planck measurements. The temperature-polarization correlation (TE) spectrum is less contaminated by astrophysical emissions than the temperature power spectrum (TT), allowing constraints that are less sensitive to foreground uncertainties to be derived. For {\\Lambda}CDM parameters, TE gives very competitive results compared to TT. For basic {\\Lambda}CDM model extensions (such as AL, {\\Sigma}m{\\nu}, or Neff ), it is still limited by the instrumental noise level in the polarization maps.

In very intense electromagnetic fields, the vacuum refractive index is expected to be modified due to nonlinear quantum electrodynamics (QED) properties. Several experimental tests using high intensity lasers have been proposed to observe electromagnetic nonlinearities in vacuum, such as the diffraction or the reflection of intense laser pulses. We propose a new approach which consists in observing the refraction, i.e. the rotation of the waveplanes of a probe laser pulse crossing a transverse vacuum index gradient. The latter is produced by the interaction of two very intense and ultra short laser pulses, used as pump pulses. At the maximum of the index gradient, the refraction angle of the probe pulse is estimated to be \\(0.2 \\times (\\frac{w_0}{10 \\mathrm{\\mu m}})^{-3} \\times \\frac{I}{1 \\mathrm{J}}\\)~picoradians, where \\(I\\) is the total energy of the two pump pulses and \\(w_0\\) is the minimum waist (fwhm) at the interaction area. Assuming the most intense laser pulses attainable by the LASERIX facility (\\(I = 25\\)~J, 30~fs fwhm duration, 800~nm central wavelength) and assuming a minimum waist of \\(w=10 \\mathrm{\\mu m}\\) (fwhm) (corresponding to an intensity of the order of \\(10^{21}\\)~W/cm\\(^2\\)), the expected maximum refraction angle is about 5~picoradians. An experimental setup, using a Sagnac interferometer, is proposed to perform this measurement.

The angular power spectra of the cosmic microwave background (CMB) temperature anisotropies reconstructed from Planck data seem to present too much gravitational lensing distortion. This is quantified by the control parameter \\(A_L\\) that should be compatible with unity for a standard cosmology. With the Class Boltzmann solver and the profile-likelihood method, for this parameter we measure a 2.6\\(\\sigma\\) shift from 1 using the Planck public likelihoods. We show that, owing to strong correlations with the reionization optical depth \\(\\tau\\) and the primordial perturbation amplitude \\(A_s\\), a \\(\\sim2\\sigma\\) tension on \\(\\tau\\) also appears between the results obtained with the low (\\(\\ell\\leq 30\\)) and high (\\(30<\\ell\\lesssim 2500\\)) multipoles likelihoods. With Hillipop, another high-\\(\\ell\\) likelihood built from Planck data, this difference is lowered to \\(1.3\\sigma\\). In this case, the \\(A_L\\) value is still in disagreement with unity by \\(2.2\\sigma\\), suggesting a non-trivial effect of the correlations between cosmological and nuisance parameters. To better constrain the nuisance foregrounds parameters, we include the very high \\(\\ell\\) measurements of the Atacama Cosmology Telescope (ACT) and South Pole Telescope (SPT) experiments and obtain \\(A_L = 1.03 \\pm 0.08\\). The Hillipop+ACT+SPT likelihood estimate of the optical depth is \\(\\tau=0.052\\pm{0.035,}\\) which is now fully compatible with the low \\(\\ell\\) likelihood determination. After showing the robustness of our results with various combinations, we investigate the reasons for this improvement that results from a better determination of the whole set of foregrounds parameters. We finally provide estimates of the \\(\\Lambda\\)CDM parameters with our combined CMB data likelihood.