A. Babic

Renormalization group running of the cosmological constant and its implication for the Higgs boson mass in the standard model

AbstractThe renormalization-group equation for the zero-point energies associated with vacuum fluctuationsof massive fields from the Standard Model is examined. Our main observation is that at any scale therunning is necessarily dominated by the heaviest degrees of freedom, in clear contradistinction with theAppelquist & Carazzone decoupling theorem. Such an enhanced running would represent a disaster forcosmology, unless a fine-tuned relation among the masses of heavy particles is imposed. In this way, weobtain m H ≃ 550 GeV for the Higgs mass, a value safely within the unitarity bound, but far above themore stringent triviality bound for the case when the validity of the Standard Model is pushed up to thegrand unification (or Planck) scale. PACS: 14.80.Bn; 95.30.Cq; 98.80.CqKeywords: Cosmological constant; Zero-point energy; Renormalization-group equation; Running;Higgs bosonThere are now increasing indications, based on observations on rich clusters of galaxies [1],searches for Type Ia Supernovae [2] and measurements of the cosmic microwave backgroundanisotropy [3], that the today’s universe is undergoing a phase of accelerated expansion. Thisis usually attributed to the presence of a cosmological constant. Although the simplest explana-tion is a time-independent (i.e. “true”) cosmological constant Λ, many scenarios have also beendiscussed involving a dynamical cosmological constant Λ(t). There have recently been a numberof suggestions regarding the nature of the latter, the most popular candidate being known under

Renormalization-group running cosmologies. A Scale-setting procedure

For cosmologies including scale dependence of both the cosmological and the gravitational constant, an additional consistency condition dictated by the Bianchi identities emerges, even if the energy-momentum tensor of ordinary matter stays individually conserved. For renormalization-group (RG) approaches it is shown that such a consistency relation ineluctably fixes the RG scale (which may have an explicit as well as an implicit time dependence), provided that the solutions of the RG equation for both quantities are known. Hence, contrary to the procedures employed in the recent literature, we argue that there is no more freedom in identification of the RG scale in terms of the cosmic time in such cosmologies. We carefully set the RG scale for the RG evolution phrased in a quantum-gravity framework based on the hypothetical existence of an infrared fixed point, for the perturbative regime within the same framework, as well as for an evolution within quantum field theory in a curved background. In the latter case, the implications of the scale setting for the particle spectrum are also briefly discussed.

The evolution of host mass and black hole mass in quasi-stellar objects from the 2dF QSO Redshift Survey

We investigate the relation between the mass of super-massive black holes (MBH) in QSOs and the mass of the dark matter halos hosting them (MDH). We measure the widths of broad emission lines (Mg ii �2798, C iv �1549) from QSO composite spectra as a function of redshift. These widths are then used to determine virial black hole mass estimates. We compare our virial black hole mass estimates to dark matter halo masses for QSO hosts derived by Croom et al. (2005) based on measurements of QSO clustering. This enables us to trace the MBH MDH relation over the redshift range z = 0.5 to 2.5. We calculate the mean zero-point of the MBH MDH relation to be MBH = 10 8.4±0.2 M⊙ for an MDH = 10 12.5 M⊙. These data are then compared with several models connecting MBH and MDH as well as recent hydrodynamical simulations of galaxy evolution. We note that the flux limited nature of QSO samples can cause a Malmquist-type bias in the measured zero-point of the MBH MDH relation. The magnitude of this bias depends on the scatter in the MBH MDH relation, and we reevaluate the zero-point assuming three published values for this scatter. We create a subsample of our data defined by a constant magnitude interval around L ∗ and find (1 + z) 3.3±1.3 evolution in MBH between z � 0.5 and 2.5 for typical, L ∗ QSOs. We also determine the Eddington ratios (L/LEdd) for the same subsample and find no significant evolution: (1 + z) −0.4±1.1 . Taken at face value, our data suggest that a decrease in active black hole mass since z � 2.5 is the driving force behind luminosity evolution of typical, L ∗ , optically selected AGN. However, we note that our data are also consistent with a picture in which reductions in both black hole mass and accretion rate contribute equally to luminosity evolution. In addition we find these evolution results are strongly affected by the virial black hole mass estimators used. Changes to the calibration of these has a significant effect on the evolution results.

Minimal variability time scale – central black hole mass relation of the γ-ray loud blazars

Context. The variability time scales of the blazar γ-ray emission contain the imprints of the sizes of their emission zones and are generally expected to be larger than the light-crossing times of these zones. In several cases the time scales were found to be as short ∼10 min, suggesting that the emission zone sizes are comparable with the sizes of the central supermassive black holes. Previously, these measurements also led to the suggestion of a possible connection between the observed minimal variability time scales and the masses of the corresponding black holes. This connection can be used to determine the location of the γ-ray emission site, which currently remains uncertain. Aims. The study aims to investigate the suggested “minimum time scale – black hole mass” relation using the blazars, detected in the TeV band. Methods. To obtain the tightest constraints on the variability time scales this work uses a compilation of observations by the Cherenkov telescopes HESS, MAGIC, and VERITAS. These measurements are compared to the blazar central black hole masses found in the literature. Results. The majority of the studied blazars show the variability time scales which are at least comparable to the period of rotation along the last stable orbit of the central black hole – and in some cases as short as its light-crossing time. For several sources the observed variability time scales are found to be smaller than the black hole light-crossing time. This suggests that the detected γ-ray variability originates, most probably, from the turbulence in the jet, sufficiently far from the central black hole.

Constraints on particle acceleration in SS433/W50 from MAGIC and H.E.S.S. observations

The large jet kinetic power and non-thermal processes occurring in the microquasar SS 433 make this source a good candidate for a very high-energy (VHE) gamma-ray emitter. Gamma-ray fluxes have been predicted for both the central binary and the interaction regions between jets and surrounding nebula. Also, non-thermal emission at lower energies has been previously reported. We explore the capability of SS 433 to emit VHE gamma rays during periods in which the expected flux attenuation due to periodic eclipses and precession of the circumstellar disk periodically covering the central binary system is expected to be at its minimum. The eastern and western SS433/W50 interaction regions are also examined. We aim to constrain some theoretical models previously developed for this system. We made use of dedicated observations from MAGIC and H.E.S.S. from 2006 to 2011 which were combined for the first time and accounted for a total effective observation time of 16.5 h. Gamma-ray attenuation does not affect the jet/medium interaction regions. The analysis of a larger data set amounting to 40-80 h, depending on the region, was employed. No evidence of VHE gamma-ray emission was found. Upper limits were computed for the combined data set. We place constraints on the particle acceleration fraction at the inner jet regions and on the physics of the jet/medium interactions. Our findings suggest that the fraction of the jet kinetic power transferred to relativistic protons must be relatively small to explain the lack of TeV and neutrino emission from the central system. At the SS433/W50 interface, the presence of magnetic fields greater 10

Multi-wavelength characterization of the blazar S5 0716+714 during an unprecedented outburst phase

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G is derived assuming a synchrotron origin for the observed X-ray emission. This also implies the presence of high-energy electrons with energies up to 50 TeV, preventing an efficient production of gamma-ray fluxes in these interaction regions.MAGIC Collaboration: M. L. Ahnen ... P. de Wilt ... S. Einecke ... J. Hawkes ... J.Lau ... N. Maxted ... G.Rowell ... F. Voisin ... et al.

Geometric programming in designing of mental models on the example of strategic thinking between synergies competition and cooperation

The BL Lac object S5~0716+714, a highly variable blazar, underwent an impressive outburst in January 2015 (Phase A), followed by minor activity in February (Phase B). The MAGIC observations were triggered by the optical flux observed in Phase A, corresponding to the brightest ever reported state of the source in the R-band. The comprehensive dataset collected is investigated in order to shed light on the mechanism of the broadband emission. Multi-wavelength light curves have been studied together with the broadband Spectral Energy Distributions (SEDs). The data set collected spans from radio, optical photometry and polarimetry, X-ray, high-energy (HE, 0.1 GeV 100 GeV) with MAGIC. The flaring state of Phase A was detected in all the energy bands, providing for the first time a multi-wavelength sample of simultaneous data from the radio band to the VHE. In the constructed SED the \textit{Swift}-XRT+\textit{NuSTAR} data constrain the transition between the synchrotron and inverse Compton components very accurately, while the second peak is constrained from 0.1~GeV to 600~GeV by \textit{Fermi}+MAGIC data. The broadband SED cannot be described with a one-zone synchrotron self-Compton model as it severely underestimates the optical flux in order to reproduce the X-ray to

Cabibbo-suppressed decays of theΩc0—Feedback to theΞc+lifetime

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-ray data. Instead we use a two-zone model. The EVPA shows an unprecedented fast rotation. An estimation of the redshift of the source by combined HE and VHE data provides a value of