Impact of trans-Planckian quantum noise on the Primordial Gravitational Wave spectrum

We investigate the impact of stochastic quantum noise due to trans--Planckian effects on the primordial power spectrum for gravity waves during inflation. Given an energy scale Lambda, expected to be close to the Planck scale m_Pl and larger than the Hubble scale H, this noise is described in terms of a source term in the evolution equation for comoving modes k which changes its amplitude growth from early times as long as the mode physical wavelength is smaller than Lambda^-1. We model the source term as due to a gas of black holes in the trans--Planckian regime and the corresponding Hawking radiation. In fact, for energy scales larger than, or of the order of Lambda, it is expected that trapped surfaces may form due to large energy densities. At later times the evolution then follows the standard sourceless evolution. We find that this mechanism still leads to a scale-invariant power spectrum of tensor perturbations, with an amplitude that depends upon the ratio Lambda/m_Pl.Comment: 6 pages, 1 figur

Neff in the Standard Model at NLO is 3.043

The effective number of relativistic neutrino species is a fundamental probe of the early Universe and its measurement represents a key constraint on many scenarios beyond the Standard Model of Particle Physics. In light of this, an accurate prediction of $N_{\rm eff}$ in the Standard Model is of pivotal importance. In this work, we consider the last ingredient needed to accurately calculate $N_{\rm eff}^{\rm SM}$: standard zero and finite temperature QED corrections to $e^+e^- \leftrightarrow \nu\bar{\nu}$ interaction rates during neutrino decoupling at temperatures around $T\sim {\rm MeV}$. We find that this effect leads to a reduction of $-0.0007$ in $N_{\rm eff}^{\rm SM}$. This NLO correction to the interaction rates, together with finite temperature QED corrections to the electromagnetic density of the plasma, and the effect of neutrino oscillations, implies that $N_{\rm eff}^{\rm SM} = 3.043$ with a theoretical uncertainty that is much smaller than any projected observational sensitivity.Comment: 4 pages, 2 figure

<math display="inline"><msub><mi>N</mi><mrow><mi>eff</mi></mrow></msub></math> in the Standard Model at NLO is 3.043

The effective number of relativistic neutrino species is a fundamental probe of the early Universe, and its measurement represents a key constraint on many scenarios beyond the Standard Model of Particle Physics. In light of this, an accurate prediction of Neff in the Standard Model is of pivotal importance. In this work, we consider the last ingredient needed to accurately calculate NeffSM: standard zero and finite-temperature QED corrections to e+e-↔νν¯ interaction rates during neutrino decoupling at temperatures around T∼MeV. We find that this effect leads to a reduction of -0.0007 in NeffSM. This next-to-leading-order QED correction to the interaction rates, together with finite-temperature QED corrections to the electromagnetic density of the plasma, and the effect of neutrino oscillations, implies that NeffSM=3.043 with a theoretical uncertainty that is much smaller than any projected observational sensitivity.The effective number of relativistic neutrino species is a fundamental probe of the early Universe and its measurement represents a key constraint on many scenarios beyond the Standard Model of Particle Physics. In light of this, an accurate prediction of $N_{\rm eff}$ in the Standard Model is of pivotal importance. In this work, we consider the last ingredient needed to accurately calculate $N_{\rm eff}^{\rm SM}$: standard zero and finite temperature QED corrections to $e^+e^- \leftrightarrow \nu\bar{\nu}$ interaction rates during neutrino decoupling at temperatures around $T\sim {\rm MeV}$. We find that this effect leads to a reduction of $-0.0007$ in $N_{\rm eff}^{\rm SM}$. This NLO QED correction to the interaction rates, together with finite temperature QED corrections to the electromagnetic density of the plasma, and the effect of neutrino oscillations, implies that $N_{\rm eff}^{\rm SM} = 3.043$ with a theoretical uncertainty that is much smaller than any projected observational sensitivity

Use of balloons and blimps to improve coverage range in Low Power Wireless Wide Area Networks

The availability of devices suitable to construct low power wireless wide area networks, offers the possibility to set up simple infrastructures for data sensing in a larger region, using simple single hop wireless sensor networks. Avoiding multi-hop routing schemes, allows to Save energy and reduces the probability of interruptions and the deployment cost. We have recently applied this solution in a hilly environment, to collect meteorological data from crops. In such an environment, when unlicensed frequencies are used, an elevated access point allows direct line-of-sight between devices. To avoid the construction of expensive towers, one possible solution is to lift the access points with balloons, blimps and kites, reaching up to 350 feet of elevation. Preliminary results are presented in the paper, together with a comparison among the technological solutions adopted for the multi and single hop cases