1,721,038 research outputs found
Higgs mass and gravity waves in standard model false vacuum inflation
No full textIn previous publications we have proposed that inflation can be realized in a second minimum of the standard model Higgs potential at energy scales of about 1016 GeV, if the minimum is not too deep and if a mechanism which allows a transition to the radiation dominated era can be found. This is provided, e.g., by scalar-tensor gravity models or hybrid models. Using such ideas we had predicted the Higgs boson mass to be of about 126±3 GeV, which has been confirmed by the LHC, and that a possibly measurable amount of gravity waves should be produced. Using more refined recent theoretical calculations of the renormalization group equations we show that such scenario has the right scale of inflation only for small Higgs mass, lower than about 124 GeV, otherwise gravity waves are overproduced. The precise value is subject to some theoretical error and to experimental errors on the determination of the strong coupling constant. Finally we show that introducing a moderately large nonminimal coupling for the Higgs field the bound can shift to larger values and be reconciled with the LHC measurements of the Higgs mass
Measuring our Peculiar Velocity by 'Pre-deboosting' the CMB
No full textIt was recently shown that our peculiar velocity β with respect to the CMB induces mixing among multipoles and off-diagonal correlations at all scales which can be used as a measurement of β, which is independent of the standard measurement using the CMB temperature dipole. The proposed techniques rely however on a perturbative expansion which breaks down for l gtrsim 1/β ≈ 800. Here we propose a technique which consists of deboosting the CMB temperature in the time-ordered data and show that it extends the validity of the perturbation analysis multipoles up to l ~ 10000. We also obtain accurate fitting functions for the mixing between multipoles valid in a full non-linear treatment. Finally we forecast the achievable precision with which these correlations can be measured in a number of current and future CMB missions. We show that Planck could measure the velocity with a precision of around 60 km/s, ACTPol in 4 years around 40 km/s, while proposed future experiments could further shrink this error bar by over a factor of around 2
The Cold Spot as a Large Void: Lensing Effect on CMB Two and Three Point Correlation Functions
No full textThe "Cold Spot" in the CMB sky could be due to the presence of an anomalous huge spherical underdense region - a "Void" - of a few hundreds Mpc/h radius. Such a structure would have an impact on the CMB two-point (power spectrum) and three-point (bispectrum) correlation functions not only at low-l, but also at high-l through Lensing, which is a unique signature of a Void. Modeling such an underdensity with an LTB metric, we show that for the power spectrum the effect should be visible already in the WMAP data if the Void radius is at least 400 Mpc/h, while it will be visible by the Planck satellite for any Void radius. We also speculate that this could be linked to the high-l detection of an hemispherical power asymmetry in the sky. Moreover, there should be non-zero correlations in the non-diagonal two-point function. For the bispectrum, the effect becomes important for squeezed triangles with two very high-l's: this signal can be detected by Planck if the Void radius is at least 600 Mpc/h. We have also estimated the contamination of the primordial non-Gaussianity f_NL due to this signal, which turns out to be negligible
On the proper kinetic quadrupole CMB removal and the quadrupole anomalies
No full textIt has been pointed out recently that the quadrupole-octupole alignment in the CMB data is significantly affected by the so-called kinetic Doppler quadrupole (DQ), which is the temperature quadrupole induced by our proper motion. Assuming our velocity is the dominant contribution to the CMB dipole we have v/c=β=(1.231 ± 0.003) × 10−3, which leads to a non-negligible DQ of Script O(β2). Here we stress that one should properly take into account that CMB data are usually not presented in true thermodynamic temperature, which induces a frequency dependent boost correction. The DQ must therefore be multiplied by a frequency-averaged factor, which we explicitly compute for several Planck CMB maps finding that it varies between 1.67 and 2.47. This is often neglected in the literature and turns out to cause a small but non-negligible difference in the significance levels of some quadrupole-related statistics. For instance the alignment significance in the SMICA 2013 map goes from 2.3σ to 3.3σ with the frequency dependent DQ, instead of 2.9σ ignoring the frequency dependence in the DQ. Moreover as a result of a proper DQ removal, the agreement across different map-making techniques is improved
On the significance of power asymmetries in Planck CMB data at all scales
No full textWe perform an analysis of the CMB temperature data taken by the Planck satellite investigating if there is any significant deviation from cosmological isotropy. We look for differences in the spectrum between two opposite hemispheres and also for dipolar modulations. We propose a new way to avoid biases due to partial-sky coverage by producing a mask symmetrized in antipodal directions, in addition to the standard smoothing procedure. We also properly take into account both Doppler and aberration effects due to our peculiar velocity and the anisotropy of the noise, since these effects induce a significant hemispherical asymmetry. We are thus able to probe scales all the way to l = 2000. After such treatment we find no evidence for significant hemispherical anomalies along any of the analyzed directions (i.e. deviations are less than 1.5σ when summing over all scales). Although among the larger scales there are sometimes higher discrepancies, these are always less than 3σ. We also find results on a dipolar modulation of the power spectrum. Along the hemispheres aligned with the most asymmetric direction for 2 ≤ l ≤ 2000 we find a 3.3σ discrepancy when comparing to simulations. However, if we do not restrict ourselves to Planck's maximal asymmetry axis, which can only be known a posteriori, and compare Planck data with the modulation of simulations along their respective maximal asymmetry directions, the discrepancy goes down to less than 1σ (with, again, almost 3σ discrepancies in some low-l modes). We thus conclude that no significant power asymmetries seem to be present in the full data set. Interestingly, without proper removal of Doppler and aberration effects one would find spurious anomalies at high l, between 3σ and 5σ. Even when considering only l < 600 we find that the boost is non-negligible and alleviates the discrepancy by roughly half-σ
Standard Model False Vacuum Inflation: Correlating the Tensor-to-Scalar Ratio to the Top Quark and Higgs Boson masses
Full text linkFor a narrow band of values of the top quark and Higgs boson masses, the standard model Higgs potential develops a false minimum at energies of about 10 16 GeV , where primordial inflation could have started in a cold metastable state. A graceful exit to a radiation-dominated era is provided, e.g., by scalar-tensor gravity models. We pointed out that if inflation happened in this false minimum, the Higgs boson mass has to be in the range 126.0 ± 3.5 GeV , where ATLAS and CMS subsequently reported excesses of events. Here we show that for these values of the Higgs boson mass, the inflationary gravitational wave background has be discovered with a tensor-to-scalar ratio at hand of future experiments. We suggest that combining cosmological observations with measurements of the top quark and Higgs boson masses represent a further test of the hypothesis that the standard model false minimum was the source of inflation in the universe
Improving Planck calibration by including frequency-dependent relativistic corrections
No full textThe Planck satellite detectors are calibrated in the 2015 release using the 'orbital dipole', which is the time-dependent dipole generated by the Doppler effect due to the motion of the satellite around the Sun. Such an effect has also relativistic time-dependent corrections of relative magnitude 10(−)(3), due to coupling with the 'solar dipole' (the motion of the Sun compared to the CMB rest frame), which are included in the data calibration by the Planck collaboration. We point out that such corrections are subject to a frequency-dependent multiplicative factor. This factor differs from unity especially at the highest frequencies, relevant for the HFI instrument. Since currently Planck calibration errors are dominated by systematics, to the point that polarization data is currently unreliable at large scales, such a correction can in principle be highly relevant for future data releases
Cosmological parameter estimation: impact of CMB aberration
No full textThe peculiar motion of an observer with respect to the CMB rest frame induces an apparent deflection of the observed CMB photons, i.e. aberration, and a shift in their frequency, i.e. Doppler effect. Both effects distort the temperature multipoles a(l)m's via a mixing matrix at any l. The common lore when performing a CMB based cosmological parameter estimation is to consider that Doppler affects only the l = 1 multipole, and neglect any other corrections. In this paper we reconsider the validity of this assumption, showing that it is actually not robust when sky cuts are included to model CMB foreground contaminations. Assuming a simple fiducial cosmological model with five parameters, we simulated CMB temperature maps of the sky in a WMAP-like and in a Planck-like experiment and added aberration and Doppler effects to the maps. We then analyzed with a MCMC in a Bayesian framework the maps with and without aberration and Doppler effects in order to assess the ability of reconstructing the parameters of the fiducial model. We find that, depending on the specific realization of the simulated data, the parameters can be biased up to one standard deviation for WMAP and almost two standard deviations for Planck. Therefore we conclude that in general it is not a solid assumption to neglect aberration in a CMB based cosmological parameter estimation
The Cold Spot as a Large Void: Rees-Sciama effect on CMB Power Spectrum and Bispectrum
No full textThe detection of a "Cold Spot" in the CMB sky could be explained by the presence of an anomalously large spherical underdense region (with radius of a few hundreds Mpc/h) located between us and the Last Scattering Surface. Modeling such an underdensity with an LTB metric, we investigate whether it could produce significant signals on the CMB power spectrum and bispectrum, via the Rees-Sciama effect. We find that this leads to a bump on the power spectrum, that corresponds to an O(5%-25%) correction at multipoles 5 < l < 50; in the cosmological fits, this would modify the \chi^2 by an amount of order unity. We also find that the signal should be visible in the bispectrum coefficients with a signal-to-noise S/N ~ O (1-10), localized at 10 < l < 40. Such a signal would lead to an overestimation of the primordial f_{NL} by an amount \Delta f_{NL} ~ 1 for WMAP and by \Delta f_{NL} ~ 0.1 for Planck
Isocurvature perturbations in the ekpyrotic universe
No full textThe Ekpyrotic scenario assumes that our visible Universe is a boundary brane in a five-dimensional bulk and that the hot Big Bang occurs when a nearly supersymmetric five-brane travelling along the fifth dimension collides with our visible brane. We show that the generation of isocurvature perturbations is a generic prediction of the Ekpyrotic Universe. This is due to the interactions in the kinetic terms between the brane modulus parametrizing the position of the five-brane in the bulk and the dilaton and volume moduli. We show how to separate explicitly the adiabatic and isocurvature modes by performing a rotation in field space. Our results indicate that adiabatic and isocurvature perturbations might be cross-correlated and that curvature perturbations might be entirely seeded by isocurvature perturbations
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