Searches for proton decay and superheavy Magnetic Monopoles

Conclusion In conclusion, as of 1984 January, it may be stated that the existence of super-heavy monopoles and the phenomenon of nucleon decay, both of which are extremely important from the point of view of grand unification theories, are still very open questions. While there has been just one magnetic monopole candidate so far, there have been several as far as nucleon decay is concerned. The first candidates for nucleon decay came from the fine-grain calorimeters of KGF, and NUSEX; recently there have been candidates from the water Cerenkov experiments as well. The experimental situation regarding the other important phenomena of relevance to grand unification which we have not discussed in this article — like the finite mass of neutrinos, neutrino oscillations, and neutron oscillations — continues to be indefinite though many dedicated experiments are in progress. With the continued operation of the nucleon decay experiments already collecting data and the commissioning of the new generation of experiments over the next few years, the stage is set for a resolution of this problem in a time scale of 5–10 years. The present indication that the dominant decay mode for the proton (even if it decays) is notp → e⁺π⁰ and that the lower limit to the lifetime of the nucleon is 10³¹ yr, does not favour the simple SU(5) type models. The remarkable discoveries of W^± and Z⁰ with mass values exactly as predicted, have given a boost to the unification based on the gauge theoretical approaches. Whether grand unification can be extended to super-unification, experiment alone can tell. This will be the challenge for the remaining years of this century.     

A diatom model of dust in the Trapezium nebula

The influence of the results of the grand unified theory of interactions on the formation of black holes is discussed and compared with the observations of the supernova 1987a.     

Dynamics of warm inflation with gauge fields in Bianchi type I universe model

In this paper, we study the dynamics of warm inflation in which slow-roll inflation is driven by non-Abelian gauge fields. To this end, we use the geometry of locally rotationally symmetric Bianchi type I universe model. We construct dynamical equations, i.e., first model field equation, energy conservation equations and equation of motion under slow-roll approximation. In order to discuss inflationary perturbations, we evaluate parameters like scalar and tensor power spectra as well as scalar and tensor spectral indices. We also evaluate inflaton, directional Hubble parameter, slow-roll and perturbation parameters as well as tensor-scalar ratio as a function of inflaton during intermediate and logamediate inflationary eras. It is concluded that anisotropic inflationary universe model with non-Abelian gauge fields remains compatible with WMAP7.     

Dark Matter from the inflaton field

We present a model where inflation and Dark Matter takes place via a single scalar field ?. Without introducing any new parameters we are able unify inflation and Dark Matter using a scalar field ? that accounts for inflation at an early epoch while it gives a Dark Matter WIMP particle at low energies. After inflation our universe must be reheated and we must have a long period of radiation dominated before the epoch of Dark Matter. Typically the inflaton decays while it oscillates around the minimum of its potential. If the inflaton decay is not complete or sufficient then the remaining energy density of the inflaton after reheating must be fine tuned to give the correct amount of Dark Matter. An essential feature here, is that Dark Matter-Inflaton particle is produced at low energies without fine tuning or new parameters. This process uses the same coupling g as for the inflaton decay. Once the field ? becomes non-relativistic it will decouple as any WIMP particle, since n_? is exponentially suppressed. The correct amount of Dark Matter determines the cross section and we have a constraint between the coupling g and the mass m_o of ?. The unification scheme we present here has four free parameters, two for the scalar potential V(?) given by the inflation parameter λ of the quartic term and the mass m_o. The other two parameters are the coupling g between the inflaton ? and a scalar filed φ and the coupling h between φ with standard model particles ψ or χ. These four parameters are already present in models of inflation and reheating process, without considering Dark Matter. Therefore, our unification scheme does not increase the number of parameters and it accomplishes the desired unification between the inflaton and Dark Matter for free.     

Dynamical supersymmetric inflation

We propose a new class of inflationary models in which the scalar field potential governing inflation is generated by the same nonperturbative gauge dynamics that may lead to supersymmetry breaking. Such models satisfy constraints from cosmic microwave background measurements for natural values of the fundamental parameters in the theory. In addition, they have two particularly interesting characteristics: a “blue” spectrum of scalar perturbations, and an upper bound on the total amount of inflation possible.     

Estimating the effect of intermediate-range forces on the mass of rapidly-rotating neutron stars

Intermediate-range gravitational forces have been predicted by certain grand unified theories. If such forces exist, they would naturally affect the structure of neutron stars. Here, a simple rotating neutron star model is constructed which, under fairly mild assumptions, can be integrated exactly for the pressure. According to this model, the effect on neutron star masses by intermediate range forces is negligible, except when the range approaches the radius of the star and the coupling constant is close to the usual gravitation constant. In addition, extremely short range forces can be shown to have negligible effect, even when the coupling constant is many orders of magnitude greater thanG. Thus, there appears to be little hope of using neutron star mass measurements to test such grand unified theories.     

Searching for relic neutralinos using neutrino telescopes

Neutrino telescopes of large area offer the possibility of searching for indirect signals of relic neutralinos in the galactic halo, due to annihilations in the Sun or the Earth. Here we investigate the sensitivity, using a supergravity scheme where the soft scalar mass terms are not constrained by universality conditions at the grand unification scale. We first discuss in which regions of the supersymmetric parameter space the neutralino may be considered as a good candidate for cold dark matter. The discovery potential of the search using neutrino telescopes is then compared to that of the direct search for relic neutralinos.     

Kinetic and chemical equilibrium of the Universe and gravitino production

Flat directions in generic supersymmetric theories can change the thermal history of the Universe. A novel scenario was proposed earlier where the vacuum expectation value of the flat directions induces large masses for all the gauge bosons and gauginos. This delays the thermalization of the Universe after inflation and solves the gravitino problem. In this article we perform a detailed calculation of the above scenario. We include the appropriate initial state particle distribution functions, consider the conditions for the feasibility of the non-thermal scenario, and investigate phase space suppression of gravitino production in the context of heavy gauge bosons and gauginos in the final state. We find that the total gravitino abundance generated is consistent with cosmological constraints.     

Self-interacting dark matter from the hidden heterotic-string sector

It has been suggested recently that self-interacting dark matter (SIDM) fits better the observational characteristics of galaxy dynamics. We propose that the SIDM is composed from the glueballs of the hidden sector non-Abelian gauge group, while the hidden matter states exist in vector-like representation and decouple from the light spectrum. It is shown that these glueballs are semi-stable with the lifetime larger than the present age of the Universe, if their mass is 1 GeV or less. The constraint on their abundance today suggests that the energy was stored in the hidden sector soon after inflation. This imposes an upper limit on the reheating temperature. We further study the naturalness of this scenario in the context of the free-fermionic string models and point out a class of such models where the SIDM from the hidden sector is indeed plausible.     

Enigmatic aspects of the early universe: possibility of a ‘pre-big bang phase’!

In this paper it is suggested that inclusion of mutual gravitational interactions among the particles in the early dense universe can lead to a ‘pre-big bang’ scenario, with particle masses greater than the Planck mass implying an accelerating phase of the universe, which then goes into the radiation phase when the masses fall below the Planck mass. The existence of towers of states of such massive particles (i.e. multiples of Planck mass) as implied in various unified theories, provides rapid acceleration in the early universe, similar to the usual inflation scenario, but here the expansion rate goes over ‘smoothly’ to the radiation dominated universe when temperature becomes lower than the Planck temperature.     

Magnetic Flux Transport Simulations of Solar Surface Magnetic Distributions During a Grand Minimum

It is well known that magnetic activity on the Sun modulates from one cycle to the next. The most striking occurrence of this is called a grand minimum where magnetic activity all but disappears. The latest grand minimum occurred between the years 1645 and 1715 and is called the Maunder minimum. In this paper magnetic flux transport simulations are used to consider what type of surface magnetic field configurations may be produced both during and after a grand minimum depending on how the grand minimum occurs. It is shown that the surface configurations during and after a grand minimum strongly depend on the phase of the cycle in which the grand minimum starts and whether it lasts for an odd or even number of cycles. If the grand minimum starts around cycle minimum then a significant amount of large-scale magnetic flux may persist on the Sun at high latitudes during the grand minimum. In contrast, if it starts at cycle maximum during the grand minimum it is possible for there to be essentially zero large-scale magnetic flux over the entire surface of the Sun. It is shown that for a single grand minimum event the reversal of the polar fields at the presently observed time in the solar cycle is only reproduced if the event starts at cycle minimum and extends over an even number of cycles. In contrast, if the grand minimum runs for an odd number of cycles it is possible for there to be no reversal of the polar fields or for the reversals to occur at times inconsistent with our present understanding of the solar cycle. Consequences of the assumptions made in the modelling are discussed and the significance of the simulations for direct modelling of events such as the Maunder minimum are considered.     

Where are the broad lines in Seyfert 2s?

The unified model for Seyfert 2s postulates that these galaxies are in fact normal Seyfert ls whose innermost regions are hidden from a direct view by an opaque torus. Galaxies seen from a line-of-sight within the opening angle of this torus have the central continuum source and the Broad Line Region unobstructed, and are classified as Seyfert 1/QSO. In Seyfert 2s, on the other hand, periscopic views of the hidden nucleus may be obtained through scattering of the nuclear light in the extranuclear regions. If this model is correct, the Blue and Featureless Continuum observed in many Seyfert 2s is simply a mirror image of the obscured nucleus. In this case, the light from the Broad Line Region must also be reflected towards the observer. Seyfert 2s should therefore exhibit broad lines in their spectrum, which, by definition, they do not! In this contribution we examine this issue and the complications it brings to the basic unification picture of Seyfert galaxies. We fail to find a consistent explanation for this question in the framework of the unified model. An alternative modified-unified model for Seyfert 2s is proposed.     

Varying Constants, Nuclear Physics and Unification

Precision measurements of gauge couplings at particle accelerators strongly suggest that the standard model fields are unified at about 10¹⁶ GeV. This talk will consist of a brief review of this evidence and also how in such a setting variations in α _em lead to much larger variations in Λ _QCD . I will then describe how variations in the strong force will impact upon nuclear astrophysics, considering in particular the stability of di-nucleons and stellar and primordial nucleosynthesis. (Based upon collaborations with T. Dent and with A. Csoto, H. Oberhummer and H. Schlattl.) This revised version was published online in July 2006 with corrections to the Cover Date.     

The unification of the inflation with late-time acceleration in Born-Infeld-f(R) gravity

We study accelerating dynamics from Born-Infeld-f(R) gravity in a simplified conformal approach without matter. In Makarenko et al. (arXiv:1404.2850 [gr-qc], 2011b) it was derived eventually any Dark Energy cosmology from above theory. In this Letter we apply the technique of Makarenko et al. (arXiv:1404.2850 [gr-qc], 2011b) to show that Born-Infeld-f(R) gravity may describe very realistic universe admitting the unification of early-time inflation with late-time acceleration. Specifically, the evolution with periodic as well as non-periodic behavior is considered with possibility to cross the phantom-divide at early or late-times.     

On M-Theory

This contribution gives a personal view on recent attempts to find a unified framework for non-perturbative string theories, with special emphasis on the hidden symmetries of supergravity and their possible role in this endeavor. A reformulation ofd = 11 supergravity with enlarged tangent space symmetry SO(1, 2) × SO(16) is discussed from this perspective, as well as an ansatz to construct yet further versions with SO(1, 1) × SO(16)^∞ and possibly even SO(1, 1)₊ × ISO(16)^∞ tangent space symmetry. It is suggested that upon “third quantization”, dimensionally reduced maximal supergravity may have an equally important role to play in this unification as the dimensionally reduced maximally supersymmetricSU(∞) Yang Mills theory.     

Long-Term Changes in Sunspot Activity,Occurrence of Grand Minima,and Their Future Tendencies

Long-term changes in the magnetic activity of the Sun were studied in terms of the empirical mode decomposition that revealed their essential modes. The occurrence of grand minima was also studied in their relation to long-term changes in sunspot activity throughout the past 11 000 yr. Characteristic timescales of long-term changes in solar activity manifest themselves in the occurrence of grand minima. A quantitative criterion has been defined to identify epochs of grand minima. This criterion reveals the important role of secular and bicentennial activity variations in the occurrence of grand minima and relates their amplitudes with the current activity level, which is variable on a millennial timescale. We have revealed specific patterns in the magnetic activity between successive grand minima which tend to recur approximately every 2300 yr but occasionally alternate with irregular changes. Such intermittent activity behavior indicates low dimensional chaos in the solar dynamo due to the interplay of its dominant modes. The analysis showed that in order to forecast activity level in forthcoming cycles, one should take into account long-term changes in sunspot activity on a ≈2300-yr timescale. The regularities revealed suggest solar activity to decrease in the foreseeable future.     

Application of the atomic configuration probability to the equilibrium calculation

This is an extension study of the grand canonical approach of the equation of state to the equilibrium calculation for radiative opacities. We discuss the construction of atomic configurations from the ion stages and excitation states of atoms. The atomic configuration is essentially important to the grand canonical approach, and also useful to the radiative opacity calculation. We present the complete formalism for the calculation of atomic configuration probabilities and population fractions. We show that the grand canonical approach provides a shortcut in the computation of thermodynamic equilibrium. We mainly discuss its use in two cases for the equilibrium calculation.     

Dilaton stabilization by massive fermion matter

The study started by Cabo and Brandenberger (J. Cosmol. Astropart. Phys. 2:15, 2009) about the Dilaton mean field stabilization thanks to the effective potential generated by the existence of massive fermions, is here extended. Three loop corrections are evaluated in addition to the previously calculated two loop terms. The results indicate that the Dilaton vacuum field tends to be fixed at a high value close to the Planck scale, in accordance with the need for predicting Einstein gravity from string theory. The mass of the Dilaton is evaluated to be also a high value close to the Planck mass, which implies the absence of Dilaton scalar signals in modern cosmological observations. These properties arise when the fermion mass is chosen to be either at a lower bound corresponding to the top quark mass, or alternatively, at a very much higher value assumed to be in the grand unification energy range. One of the three 3-loop terms is exactly evaluated in terms of Master integrals. The other two graphs are however evaluated in their leading logarithm correction in the perturbative expansion. The calculation of the non leading logarithmic contribution and the inclusion of higher loops terms could made more precise the numerical estimates of the vacuum field value and masses, but seemingly are expected not to change the qualitative behavior obtained. The validity of the here employed Yukawa model approximation is argued for small value of the fermion masses with respect to the Planck one. A correction to the two loop calculation done in the previous work is here underlined.     

How does inflation depend upon the nature of fluids filling up the universe in brane world scenario?

By constructing different parameters which are able to give us the information about our universe during inflation, (specially at the start and the end of the inflationary universe) a brief idea of brane world inflation is given in this work. What will be the size of the universe at the end of inflation, i.e., how many times will it grow than the original size is been speculated and analysed thereafter. Different kinds of fluids are taken to be the matter inside the brane. It is observed that in the case of highly positive pressure giving gas like polytropic, the size of the universe at the end of inflation is comparatively smaller. Whereas for negative pressure creators (like Chaplygin gas) this size is much bigger. Except these two cases, inflation has been studied for barotropic fluid and linear red shift parametrization ω(z)=ω ₀+ω ₁ z too. For them the size of the universe after inflation is much more high. We also have seen that this size does not depend upon the potential energy at the end of the inflation. On the contrary, there is a high impact of the initial potential energy upon the size of inflation.     

The origin of the Big-Bang

Within the framework of FLRW cosmology withk=+1 a singularity free model of the Universe is proposed which readily accounts for the origin of the Big-Bang and for the preponderance of matter over anti-matter. It is also free from the problems of accounting for the observed large-scale homogeneity and isotropy of the Universe as well as from the problems of horizon and flatness. It is pointed out that the collapsing universe might have acted as an ultra-high energy particle accelerator. In the collapsing phase of the Universe, when the interparticle distances10^–16 cm, the electromagnetic and weak interactions might have unified into electroweak interaction and as the collapse proceeded further the entire matter in the Universe might have been converted into quark-gluon plasma permeated by leptons. The gravitational energy released during the collapse might have been locked in this plasma. Ass approached 10^–28 cm, grand unification of electroweak and strong interactions might have occurred. It is also suggested that, with further collapse, whens<10^–33 cm super-symmetry (SUSY)—i.e., the unification of all the four interactions (viz., electromagnetic, weak, strong, and gravitational) might have occurred. During this process gravitinos, the supersymmetric partners of graviton might have been produced. As a result of the exchange of a pair of virtual gravitinos between two particles an ultra-strong repulsive force between them might have been generated. Due to this ultra-strong repulsive interaction between particles the motion of the Universe might have been reversed, i.e., the Universe might have started expanding. During expansion, whens10^–28 cm, SUSY might have broken down spontaneously toSU ₅ and gravity. Ass increased from 10^–28 to 10^–16 cm, the gravitational energy locked in the quark-gluon plasma might have been released with a gigantic explosion, the so-called Big-Bang. It is estimated here that during this Big-Bang more than 10⁸² GeV of energy might have been released. Whens10^–16 cm,SU ₅ might have broken down spontaneously toSU ₃ andU ₁. Expansion beyond this stage might have occurred in the manner described by the standard cosmology. It is further suggested that in due course of time expansion will be followed by contraction and the cycle of contraction-expansion-contraction will be repeated ad infinitum.