Cosmology, Gravitational Waves and Particles

The following sections are included:

• Preface
• Contents

Advanced Virgo is the French-Italian second generation laser gravitational wave detector, successor of the Initial Virgo. This new interferometer keeps only the infrastructure of its predecessor and aims to be 10 times more sensitive, with its first science run planned for 2017. This article gives an overview of the Advanced Virgo design and the technical choices behind it. Finally, the up-to-date progresses and the planned upgrade for the following years are detailed.

The discovery of gravitational waves enabled assessment of the science benefits of new improved gravitational wave detectors. This paper discusses the science benefits of an Asia-Australia Gravitational wave Observatory (AAGO) consisting of a pair of widely spaced gravitational wave detectors on a north-south axis. Initial sensitivity would be ∼4 times better than the projected sensitivity of Advanced LIGO, but designed for future upgrades to match proposed third generation detectors. AAGO would enable near optimum angular resolution of sources, and signal detections at a rate ∼1 per hour, sufficient to monitor a substantial fraction of all large mass black hole merger events in the universe. The proposed conceptual design and infrastructure, technical issues and challenges are discussed.

Recent detections of gravitational waves by the LIGO detectors herald a new era of observational astronomy. Previously invisible objects and phenomena may now be uncovered through their gravitational interaction. Observation of gravitational waves allows one to explore the extremes of the Universe and study astronomy and fundamental physics like never before. This article gives a brief overview of the detection process, from the production of the data to their physical implications.

The theoretical basis for the energy carried away by gravitational waves that an isolated gravitating system emits was first formulated by Hermann Bondi during the ’60s. Recent findings from the observation of distant supernovae revealed that the rate of expansion of our universe is accelerating, which may be well explained by sticking a positive cosmological constant into the Einstein field equations for general relativity. By solving the Newman–Penrose equations (which are equivalent to the Einstein field equations), we generalize this notion of Bondi mass–energy and thereby provide a firm theoretical description of how an isolated gravitating system loses energy as it radiates gravitational waves, in a universe that expands at an accelerated rate. This is in line with the observational front of LIGO’s first announcement in February 2016 that gravitational waves from the merger of a binary black hole system have been detected.

The direct discovery of gravitational waves opens of new avenues for exploring fundamental microscopic physics. In this presentation, I will illustrate this by obtaining the stringent bounds on the scale of quantum fuzziness of hypothetical noncommutative space-time. I also discuss how future observations of stochastic gravitational wave back-ground can shed light on the nature of the Higgs mechanism of the electroweak symmetry breaking and the related cosmological phase transition.

We present a theory of weak gravity parametrized by a fundamental frequency ${\omega }_0=\sqrt{1-qH}$ of the cosmological horizon, where H and q denote the Hubble and, respectively, deceleration parameter. It predicts (i) a C⁰ onset to weak gravity across accelerations α = a_dS in galaxy rotation curves, where a_dS = cH denotes the de Sitter acceleration with velocity of light c, and (ii) fast evolution Q(z) = dq(z)/dz of the deceleration parameter by $\text{Λ}={\omega }_0^2$ satisfying Q₀ > 2.5, Q₀ = Q(0), distinct from Q₀ ≲ 1 in ΛCDM. The first is identified in the high resolution data of Lelli et al. (2017), the second in the heterogeneous data on H(z) over 0 < z < 2. A model-independent cubic fit in the second rules out ΛCDM by 4.35σ and obtains H₀ = 74.0±2.2 km s⁻¹ Mpc⁻¹ consistent with Riess et al. [Astrophys. J. 826, 56 (2016)]. Comments on possible experimental tests by the LISA Pathfinder are included.

In N = 1 supergravity the tree-level scalar potential of the hidden sector may have a minimum with broken local supersymmetry (SUSY) as well as a supersymmetric Minkowski vacuum. These vacua can be degenerate, allowing for a consistent implementation of the multiple point principle. The first minimum where SUSY is broken can be identified with the physical phase in which we live. In the second supersymmetric phase, in flat Minkowski space, SUSY may be broken dynamically either in the observable or in the hidden sectors inducing a tiny vacuum energy density. We argue that the exact degeneracy of these phases may shed light on the smallness of the cosmological constant. Other possible phenomenological implications are also discussed. In particular, we point out that the presence of such degenerate vacua may lead to small values of the quartic Higgs coupling and its beta function at the Planck scale in the physical phase.

We discuss the hypothesis that the constituents of dark matter in the galactic halo are primordial intermediate-mass black holes (PIMBHs). The status of axions and weakly interacting massive particles (WIMPs) is discussed, as are the methods for detecting PIMBHs with emphasis on microlensing. The role of the angular momentum $\mathcal{J}$ of the PIMBHs in their escaping previous detection is considered.

After the results of Run I, can we still “guarantee” the discovery of supersymmetry at the LHC? It is shown that viable dark matter candidates in CMSSM-like models tend to lie in strips (coannihilation, funnel, focus point) in parameter space. The role of grand unification in constructing supersymmetric models is discussed and it is argued that nonsupersymmetric GUTs such as SO(10) may provide alternative solutions to many of the standard problems addressed by supersymmetry.

We set to weigh the black holes at their event horizons in various spacetimes and obtain masses which are substantially higher than their asymptotic values. In each case, the horizon mass of a Schwarzschild, Reissner–Nordström, or Kerr black hole is found to be twice the irreducible mass observed at infinity. The irreducible mass does not contain electrostatic or rotational energy, leading to the inescapable conclusion that particles with electric charges and spins cannot exist inside a black hole. This is proposed as the External Energy Paradigm. A higher mass at the event horizon and its neighborhood is obligatory for the release of gravitational waves in binary black hole merging. We describe how these horizon mass values are obtained in the quasi-local energy approach and applied to the black holes of the first gravitational waves GW150914.

A simple model is constructed based on the gauge symmetry SU(3)_c×SU(2)_L×U(1)_Y × SU(2)_l, with only the leptons transforming nontrivially under SU(2)_l. The extended symmetry is broken down to the Standard Model gauge group at TeV-scale energies. We show that this model provides a mechanism for baryogenesis via leptogenesis in which the lepton number asymmetry is generated by SU(2)_l instantons. The theory also contains a dark matter candidate — the SU(2)_l partner of the right-handed neutrino.

In this year, in which we celebrate 100 years of the cosmological term, ∧, in Einstein’s gravitational field equations, we are still facing the crucial question whether ∧ is truly a fundamental constant or a mildly evolving dynamical variable. After many theoretical attempts to understand the meaning of ∧, and in view of the enhanced accuracy of the cosmological observations, it seems now mandatory that this issue should be first settled empirically before further theoretical speculations on its ultimate nature. In this review, we summarize the situation of some of these studies. Devoted analyses made recently show that the ∧ = const. hypothesis, despite being the simplest, may well not be the most favored one. The overall fit to the cosmological observables SNIa + BAO + H(z) + LSS + BBN + CMB single out the class of “running” vacuum models (RVMs), in which ∧ = ∧(H) is an affine power-law function of the Hubble rate. It turns out that the performance of the RVM as compared to the “concordance” ∧CDM model (with ∧ = const.) is much better. The evidence in support of the RVM may reach ∼ 4σ c.l., and is bolstered with Akaike and Bayesian criteria providing strong evidence in favor of the RVM option. We also address the implications of this framework on the tension between the CMB and local measurements of the current Hubble parameter.

The weak bosons are not elementary gauge bosons, but bound states of two fermions. Here the excitations of the weak bosons and the new fermions are discussed — they might provide the dark matter in the universe.

The matter-antimatter asymmetry problem, corresponding to the virtual nonexistence of antimatter in the universe, is one of the greatest mysteries of cosmology. According to the prevailing cosmological model, the universe was created in the so-called ‘Big Bang’ from pure energy and it is generally considered that the Big Bang and its aftermath produced equal numbers of particles and antiparticles, although the universe today appears to consist almost entirely of matter rather than antimatter. This constitutes the matter-antimatter asymmetry problem: where have all the antiparticles gone? Within the framework of the Generation Model (GM) of particle physics, it is demonstrated that the asymmetry problem may be understood in terms of the composite leptons and quarks of the GM. It is concluded that there is essentially no matter-antimatter asymmetry in the present universe and that the observed hydrogen-antihydrogen asymmetry may be understood in terms of statistical fluctuations associated with the complex many-body processes involved in the formation of either a hydrogen atom or an antihydrogen atom.

In light of the latest neutrino data, we revisit a minimal seesaw model with the Frampton–Glashow–Yanagida ansatz. Renormalization-group running effects on neutrino masses and flavor mixing parameters are discussed and found to essentially have no impact on testing such a minimal scenario in low-energy neutrino experiments. However, since renormalization-group running can modify neutrino mixing parameters at high energies, it does affect the leptogenesis mechanism, which is responsible for the observed matter–antimatter asymmetry in our Universe. Furthermore, to ease the conflict between the naturalness argument and the successful leptogenesis, a special regime for resonant leptogenesis is also emphasized.

The following sections are included:

• Gauging orientation on a differentiable manifold (classical configurations)
• References

I describe the phenomenology of a model of supersymmetry breaking in the presence of a tiny (tuneable) positive cosmological constant. It utilizes a single chiral multiplet with a gauged shift symmetry, that can be identified with the string dilaton (or an appropriate compactification modulus). The model is coupled to the MSSM, leading to calculable soft supersymmetry breaking masses and a distinct low energy phenomenology that allows to differentiate it from other models of supersymmetry breaking and mediation mechanisms. We also study the question if this model can lead to inflation by identifying the dilaton with the inflaton. We find that this is possible if the Kähler potential is modified by a term that has the form of NS5-brane instantons, leading to an appropriate inflationary plateau around the maximum of the scalar potential, depending on two extra parameters.

We emulate Cabibbo by assuming a kind of universality for fermion mass terms in the Standard Model. We show that this is consistent with all current data and with the concept that deviations from what we term Higgs’ universality are due to corrections from currently unknown physics of nonetheless conventional form. The application to quarks is straightforward, while the application to leptons makes use of the recognition that Dark Matter can provide the “sterile” neutrinos needed for the seesaw mechanism. Requiring agreement with neutrino oscillation results leads to the prediction that the mass eigenstates of the sterile neutrinos are separated by quadratically larger ratios than for the charged fermions. Using consistency with the global fit to LSND-like, short-baseline oscillations to determine the scale of the lowest mass sterile neutrino strongly suggests that the recently observed astrophysical 3.55 keV γ-ray line is also consistent with the mass expected for the second most massive sterile neutrino in our analysis.

Within the Standard Model, using the facility of making Weak Basis transformations, attempt has been made to examine the most general mass matrices within the texture zero approach. For the case of quarks, interestingly, one finds a particular set of texture four zero quark mass matrices emerging out to be a unique viable option for the description of quark mixing data as well as for accommodation of CP violation. Similarly, general lepton mass matrices, essentially considered as texture zero mass matrices, yield interesting bounds on the CP violating Jarlskog’s rephasing invariant parameter in the leptonic sector.

Issue of CP invariance in the flavor sector has been revisited briefly. Apart from defining the CP invariants in the quark sector as well as in the leptonic sector, we have briefly attempted to find Dirac like leptonic CP violating phase δ_l using analogy of the CP violating phase in the quark sector. Also briefly reviewed in leptonic sector is the importance of CP invariants for texture two zero mass matrices in the flavor basis.

The Standard model of particle physics is a very successful theory of strong weak and electromagnetic interactions. This theory is perturbative at sufficiently high energies and renormalizable, it describes these interactions at quantum level. However it has a number of limitations, one being the fact that it has 28 free parameters assuming massive neutrinos. Within the Standard model these parameters can not be explained, however they can be accommodated in the standard theory. Particularly the masses of the fermions are not predicted by the theory. The existence of the neutrino masses can be regarded as the first glimpse of the physics beyond the standard model. we have described the quark and lepton masses and mixings in context of four zero texture (FZT). In the four zero texture case the fermion masses and mixing can be related. We have made some predictions using tribimaximal mixing, the near tribimaximal (TBM) mixing. Our results show that under the TBM the neutrinos have normal, but weak hierarchy. Under near tribimaximal mixing, we find that the neutrino masses in general increase, if the value of solar angle increases from its TBM value and vice versa. It appears that the neutrinos become more and more degenerate for solar angle values higher than TBM value and hierarchical for lower values of solar angle.

Radiative neutrino mass models and the seesaw models are viewed from the unifying framework of standard model effective operators that explicitly violate lepton number by two units (ΔL = 2). After some comments on naturalness and leptogenesis in the minimal type 1 seesaw model, a full list of minimal renormalisable models that produce mass dimension-7, ΔL = 2 operators at low energies is presented. By way of example, phenomenological bounds from Run 1 LHC and lepton flavour violation data are then placed on one of these models. A possible connection between radiative neutrino mass models and the current flavour anomalies in b → c and b → s transitions is then described.

We give some new insights into the effective Majorana neutrino mass 〈m〉_ee responsible for the neutrinoless double-beta (0v2β) decays. We put forward a three-dimensional way of plotting |〈m〉_ee| against the lightest neutrino mass and the Majorana phases, which can provide more information as compared with the two-dimensional one. With the help of such graphs we discover a novel threshold of |〈m〉_ee| in terms of the neutrino masses and flavor mixing angles: |〈m〉_ee|_* = m₃ sin² θ₁₃ in connection with $\tan {\theta }_{12}=\sqrt{m_1/m_2}$ and ρ = π, which can be used to signify observability of the future 0v2β-decay experiments. Fortunately, the possibility of |〈m〉_ee| < |〈m〉_ee|_* turns out to be very small, promising a hopeful prospect for the 0v2β-decay searches.

The spin-charge-family theory, which is a kind of the Kaluza-Klein theories in d = (13+1) — but with the two kinds of the spin connection fields, the gauge fields of the two Clifford algebra objects, S^ab and ${\tilde{S}}^{ab}$ — explains all the assumptions of the standard model: The origin of the charges of fermions appearing in one family, the origin and properties of the vector gauge fields of these charges, the origin and properties of the families of fermions, the origin of the scalar fields observed as the Higgs’s scalar and the Yukawa couplings. The theory explains several other phenomena like: The origin of the dark matter, of the matter-antimatter asymmetry, the “miraculous” triangle anomaly cancellation in the standard model and others. Since the theory starts at d = (13 + 1) the question arises how and at which d had our universe started and how it came down to d = (13+1) and further to d = (3 + 1). In this short contribution some answers to these questions are presented.

Though the expansion of a simple FLRW dust ball would always decelerate in Newtonian gravitational dynamics, in GR, when the dust ball’s radius insufficiently exceeds the Schwarzschild value, its expansion instead accelerates because the dominant gravitational time-dilation braking of its expansion speed weakens as it expands. But in “comoving coordinates” the fixing of the 00 component of the metric tensor to unity completely eliminates gravitational time dilation, which is reflected by the purely Newtonian Friedmann equation of motion in those “coordinates” for the dust-ball. For a particular dust-ball initial condition Oppenheimer and Snyder remedied the GR-inconsistent Newtonian behavior in “comoving coordinates” by their famed tour-de-force analytic transformation to GR-compatible “standard” coordinates. Recent extension of their transformation to arbitrary dust-ball initial conditions enables the derivation of GR-consistent equations of motion in “standard” coordinates for all shell radii of any simple FLRW dust ball. These non-Newtonian equations of motion not only show that a dust ball’s expansion always accelerates when its radius insufficiently exceeds the Schwarzschild value, but also that for a range of initial conditions the dust ball’s expansion never ceases to accelerate (although that acceleration asymptotically decreases toward zero), apparently eliminating any need for a nonzero “dark energy” cosmological constant.

Physical and methematical implications of nonlinear-supersymmetric general relativity theory(NLSUSYGR) are presented. They offer a new paradigm for the supersymmetric unification of space-time(Einstein general relativity theory(EGR)) and matter(the SM of particle physics), which gives new insight into the unsolved problems in EGR and SM.