Running vacuum in the Universe and the time variation of the fundamental constants of Nature

We compute the time variation of the fundamental constants (such as the ratio of the proton mass to the electron mass, the strong coupling constant, the fine-structure constant and Newton’s constant) within the context of the so-called running vacuum models (RVMs) of the cosmic evolution. Recently, compelling evidence has been provided that these models are able to fit the main cosmological data (SNIa+BAO+H(z)+LSS+BBN+CMB) significantly better than the concordance \(\Lambda \)CDM model. Specifically, the vacuum parameters of the RVM (i.e. those responsible for the dynamics of the vacuum energy) prove to be nonzero at a confidence level \({\gtrsim } 3\sigma \). Here we use such remarkable status of the RVMs to make definite predictions on the cosmic time variation of the fundamental constants. It turns out that the predicted variations are close to the present observational limits. Furthermore, we find that the time evolution of the dark matter particle masses should be crucially involved in the total mass variation of our Universe. A positive measurement of this kind of effects could be interpreted as strong support to the “micro–macro connection” (viz. the dynamical feedback between the evolution of the cosmological parameters and the time variation of the fundamental constants of the microscopic world), previously proposed by two of us (HF and JS).     

Low-mass photinos and supernova 1987A

Photinos or higgsinos with mass O(100) eV are not excluded by cosmological considerations, and their radiative decays could be responsible for the surprisingly large ultra-violet background recently detected at a red-shift z∼4. The agreement of the neutrino data from supernova 1987A with standard expectations severely restricts the energy which could have been emitted via such light photinos or higgsinos, and hence constrains the parameters of models in which they appear. In the low-mass photino case, we find that squark masses between ∼60 GeV and ∼2.5 TeV are excluded. This together with laboratory limits excludes the range of squark masses generally favoured by naturalness arguments. In the low-mass higgsino case, we exclude much of the range of ratios of Higgs VEVs favoured by many models.     

Is cosmology compatible with sterile neutrinos?

By combining data from cosmic microwave background experiments (including the recent WMAP third year results), large scale structure, and Lyman-alpha forest observations, we constrain the hypothesis of a fourth, sterile, massive neutrino. For the 3 massless+1 massive neutrino case, we bound the mass of the sterile neutrino to ms<0.26 eV (0.44 eV) at 95% (99.9%) C.L., which excludes at high significance the sterile neutrino hypothesis as an explanation of the LSND anomaly. We generalize the analysis to account for active neutrino masses and the possibility that the sterile abundance is not thermal. In the latter case, the contraints in the plane are nontrivial. For a mass of >1 or <0.05 eV, the cosmological energy density in sterile neutrinos is always constrained to be omeganu<0.003 at 95% C.L., but for a mass of approximately 0.25 eV, omeganu can be as large as 0.01.     

Massive neutrinos and cosmology

The present experimental results on neutrino flavour oscillations provide evidence for non-zero neutrino masses, but give no hint on their absolute mass scale, which is the target of beta decay and neutrinoless double-beta decay experiments. Crucial complementary information on neutrino masses can be obtained from the analysis of data on cosmological observables, such as the anisotropies of the cosmic microwave background or the distribution of large-scale structure. In this review we describe in detail how free-streaming massive neutrinos affect the evolution of cosmological perturbations. We summarize the current bounds on the sum of neutrino masses that can be derived from various combinations of cosmological data, including the most recent analysis by the WMAP team. We also discuss how future cosmological experiments are expected to be sensitive to neutrino masses well into the sub-eV range.     

On the cosmological effects of thermal masses in the era 1011K⩾T⩾5xl09K

The cosmological effects of thermal masses of particles (masses induced via interactions at nonzero temperature) as well as ordinary masses are studied. These effects are shown to be negligible for photons. For electrons, however, they modify the dependence of the universe's radiusR and the timet on temperature.     

Primordial inflation with flat supergravity potentials

A new class of primordial inflation models (PRIMO) is presented, based upon the possibility of getting naturally flat potentials in N = 1 supergravity. These models may be considered as the natural cosmological extension of some recently proposed no-scale particle physics models, where all mass scales are derived from the Planck mass (M_p). PRIMO seem to satisfy all presently known cosmological constraints and they are guaranteed (a) to be void of SUSY minima with negative cosmological constant, (b) of a stable (around the origin) potential form against finite temperature effects.     

Higgs masses in the standard,multi-Higgs and supersymmetric models

Theoretical constraints and limits on the masses of Higgs scalars in the standard electroweak model, in electroweak models with additional Higgs doublets and in various supersymmetric models are presented. In the standard model, the lower limit on the Higgs mass, based on vacuum stability arguments, is reviewed in detail, as are “upper limits” based on perturbative constraints. In most grand unified and all supersymmetric models, however, at least two doublets are needed. The masses of the various Higgs scalars in the two-doublet model are discussed and constraints on their masses are found, including the generalization of the above limits. The results are then generalized to models with more than two doublets. Finally, recent attempts at constructing models with low-energy supersymmetry are reviewed and it is shown that in many models, fairly stringent tree-level mass relations among the Higgs scalars can be found. These relations are interesting in that they do not refer to the supersymmetric partners of ordinary particles, and they are most restrictive in models in which the supersymmetry is explicitly broken, i.e., via arbitrary mass terms.     

Zum gegenwärtigen Stand der Diracschen kosmologischen Hypothesen

Diracs two hypotheses about variation of the constant of gravitation and of the mass of the universe are discussed with regard to the remarks made byFierz concerning the authors attempt to give a coherent theory leading toDiracs two cosmological laws as its consequences. Though at first sight it seems that the results ofFierz would be contrary to the idea of any inconstancy of the mass of the universe, they do not make impossible a theory allowing separate threedimensional spaces to unite and to add their masses. A direct measurement of the variation of the constant of gravitation is not yet possible, but further progress of methods of measurement probably will allow a direct examination of this hypothesis. Many facts in the realm of geology and geophysics, and concerning the structure and history of the moon, to be discussed in detail elsewhere, indicate very strongly that diminution of the constant of gravitation during the development of the universe is an empirical fact. At the other handAmbarzumians results about formation of stars and galaxies strongly support the idea that these processes may be interpreted at the basis of uniting spaces.     

Charged Randall-Sundrum Braneworld Type II with Higher Order Curvature Corrections from Superstring Arguments and Dominated by Quintessence

We discuss a new class of RSII braneworld cosmology exhibiting accelerated expansion and dominated by quintessence. It is explicitly demonstrated that the universe expansion history （transition from inflation to deceleration epoch to acceleration and effective quintessence era） may naturally occur in such unified theory for some classes of inverse scalar potentials. Besides a decaying effective cosmological constant, the model incorporates an increasing black hole mass, an increasing Maxwellian electrical charge with cosmic time and a time-dependent brahe tension. The cosmological model exhibits several features of cosmological and astrophysical interest for both the early and late universe consistent with recent observations, in particular the ones concerned with the gravitational constants, black holes masses and charges and variation of the gauge coupling parameters with cosmic time. One interesting mark of the constructed model concerns the fact that a black hole mass surrounded by quintessence energy may increase with time even if the horizon disappears.     

A Class of Elementary Particle Models Without Any Adjustable Real Parameters

Conventional particle theories such as the Standard Model have a number of freely adjustable coupling constants and mass parameters, depending on the symmetry algebra of the local gauge group and the representations chosen for the spinor and scalar fields. There seems to be no physical principle to determine these parameters as long as they stay within certain domains dictated by the renormalization group. Here however, reasons are given to demand that, when gravity is coupled to the system, local conformal invariance should be a spontaneously broken exact symmetry. The argument has to do with the requirement that black holes obey a complementarity principle relating ingoing observers to outside observers, or equivalently, initial states to final states. This condition fixes all parameters, including masses and the cosmological constant. We suspect that only examples can be found where these are all of order one in Planck units, but the values depend on the algebra chosen. This paper combines findings reported in two previous preprints (G. ’t Hooft in [gr-qc], 2010; [gr-qc], 2010) and puts these in a clearer perspective by shifting the emphasis towards the implications for particle models.     

Neutrino masses and the dark energy equation of state: relaxing the cosmological neutrino mass bound

At present, cosmology provides the nominally strongest constraint on the masses of standard model neutrinos. However, this constraint is extremely dependent on the nature of the dark energy component of the Universe. When the dark energy equation of state parameter is taken as a free (but constant) parameter, the neutrino mass bound is sigma m(v) < or = 1.48 eV (95% C.L.), compared with sigma m(v) < or = 0.65 eV (95% C.L.) in the standard model where the dark energy is in the form of a cosmological constant. This has important consequences for future experiments aimed at the direct measurement of neutrino masses. We also discuss prospects for future cosmological measurements of neutrino masses.     

Light gauginos: Masses and instabilities

Within the framework of supergravity models without grand unified steps, we analyse in detail the consequences of the hypothesis that gauginos have no bare masses due to supergravity interactions. To this purpose we have made a one-loop calculation of wino, zino, and photino masses and a renormalization group improved two-loop calculation of the gluino masses.We find that: (i) the non-observation of charged winos is compatible either with a gravitino mass m ? 300 GeV or $\text{m ?3}\text{TeV}$; (ii) with a top quark mark of about 40 GeV, gluino and photino have very similar masses ranging from O(1 GeV) to O(20 GeV). In most cases consistency with cosmology requires that the gauge singlet needed to break the SU(2) × U(1) symmetry, be the lightest stable supersymmetric particle, with a mass as low as 1 keV or less. In such cases photino (or gluino) lifetimes into one photon (gluon) and one light singlet fermion (zerino), are typically between 10^?3 and 1 sec.We discuss the problem of the experimental detection of gauginos, which, according to the various options, require rather different approaches.     

Negative mass in general relativity

Mechanics is considered in a universe containing negative mass. Demanding (i) conservation of momentum, (ii) principle of equivalence, (iii) no runaway motions, (iv) no Schwarzschild black holes, and (v) the inertial and active gravitational masses of a body shall have the same sign, we find thatall mass must be negative. Some properties of such a universe are investigated. We show that a neutral spherical body of arbitrarily small size is possible, and observers external to it can communicate with each other by light rays without horizon problems. There are no cosmological models with a power-law big bang, and there is an abundance of nonsingular models. Like electric charges would attract each other, and unlike ones would repel. This could produce stars and galaxies held together by charge and not gravity. The investigation does not suggest any reason why mass in the real universe should be positive.     

The cosmological constant and the gravitational light bending

The solution of the null non-radial geodesic in a Schwarzschild-de Sitter background is revisited. The gravitational bending of a light ray is affected by the cosmological constant, in agreement with the findings of some previous investigations. The present study confirms that the leading correction term depends directly not only on Λ but also on the impact parameter and on the angular distance to the source. Using the resulting lens equation, the projected mass of the lens was estimated for several systems displaying Einstein rings. Corrections on the masses due to Λ are, on the average, of the order of 2%, indicating that they are not completly negligible for lens systems at cosmological distances.     

Hypothesis of friedmons as dark matter particles

The hypothesis of friedmons, the particles of mass 1.53 · 10^?15 g, as candidates to dark matter particles is presented. Friedmons are stable bicolor lepton structures corresponding to exact symmetry group SU(2), the dual group of electroweak interaction. Similarly to the fact that the nucleon mass is related to the average star mass, the friedmon mass is related to the mass of the Metagalaxy whose metric is close to the de Sitter metric and which can be qualitatively considered as a white hole with an event horizon defined by the cosmological constant.     

Uniform Newtonian models with variable mass

A Newtonian version of the spatially homogeneous and isotropic cosmological models with variable mass is presented. Under the assumption that the mass variation is a strict cosmological effect, its influence on the evolution of the scale function is established for the case of a dust-filled universe. Unlike the usual Newtonian models the present value of the deceleration parameter (q 1) obtained from the luminosity distance versus redshift relation can be fitted for a time-decreasing mass. It is also shown that the hyperbolic, parabolic or elliptic character of the fluid motion can be modified along the expansion. Likewise, a Friedmann-type equation with a variable curvature term indicates that in the frame-work of a full geometric variable mass theory, the same may occur with the open, flat or closed character of the universe spatial section.     

Decaying warm dark matter and neutrino masses

Neutrino masses may arise from spontaneous breaking of ungauged lepton number. Because of quantum gravity effects the associated Goldstone boson - the majoron - will pick up a mass. We determine the lifetime and mass required by cosmic microwave background observations so that the massive majoron provides the observed dark matter of the Universe. The majoron decaying dark matter scenario fits nicely in models where neutrino masses arise via the seesaw mechanism, and may lead to other possible cosmological implications.     

Physics of Dark Energy Particles

We consider the astrophysical and cosmological implications of the existence of a minimum density and mass due to the presence of the cosmological constant. If there is a minimum length in nature, then there is an absolute minimum mass corresponding to a hypothetical particle with radius of the order of the Planck length. On the other hand, quantum mechanical considerations suggest a different minimum mass. These particles associated with the dark energy can be interpreted as the “quanta” of the cosmological constant. We study the possibility that these particles can form stable stellar-type configurations through gravitational condensation, and their Jeans and Chandrasekhar masses are estimated. From the requirement of the energetic stability of the minimum density configuration on a macroscopic scale one obtains a mass of the order of 10⁵⁵ g, of the same order of magnitude as the mass of the universe. This mass can also be interpreted as the Jeans mass of the dark energy fluid. Furthermore we present a representation of the cosmological constant and of the total mass of the universe in terms of ‘classical’ fundamental constants.     

Particle physics models of inflation and curvaton scenarios

We review the particle theory origin of inflation and curvaton mechanisms for generating large scale structures and the observed temperature anisotropy in the cosmic microwave background (CMB) radiation. Since inflaton or curvaton energy density creates all matter, it is important to understand the process of reheating and preheating into the relevant degrees of freedom required for the success of Big Bang Nucleosynthesis. We discuss two distinct classes of models, one where inflaton and curvaton belong to the hidden sector, which are coupled to the Standard Model gauge sector very weakly. There is another class of models of inflaton and curvaton, which are embedded within Minimal Supersymmetric Standard Model (MSSM) gauge group and beyond, and whose origins lie within gauge invariant combinations of supersymmetric quarks and leptons. Their masses and couplings are all well motivated from low energy physics, therefore such models provide us with a unique opportunity that they can be verified/falsified by the CMB data and also by the future collider and non-collider based experiments. We then briefly discuss the stringy origin of inflation, alternative cosmological scenarios, and bouncing universes.