Modern Physics Letters A

This is a review of our present knowledge of neutrino properties and what remains to be determined. It is followed by a description of double beta decay and very high energy neutrinos. Finally, there is a description of leptogenesis. In this talk I will neglect sterile neutrinos, and thus the LSND problem.

I review the status of development of the PLANCK project which is slated for launch mid-2008. In particular, I illustrate the type of scientific results to expect in light of the current knowledge of the two on-board instruments. Indeed both instruments have now been delivered to industry for integration and they have been fully tested. This leads us to anticipate that the steady and fast rate of progress enjoyed by cosmology, in particular through the constraints given by the analysis of the Cosmic Microwave background (CMB) will continue unabated in the years to come.

Progress has been made in understanding the origin of spiral galaxies, but elliptical galaxy formation continues to pose many problems. At the centres of ellipticals, one finds supermassive black holes which are occasionally fed by gas accretion from their surroundings and are visible as active galactic nuclei. Negative feedback, due to the outflow from the central black hole during its active phase, terminates the gas supply to the spheroid, thereby resulting in an old stellar population. A contemporaneous phase of positive feedback when the protogalaxy is forming could result in the highly efficient phase of early star formation required by the recent data.

For suitable cosmological backgrounds, thermal fluctuations of a gas of strings can generate a scale-invariant spectrum of cosmological fluctuations without requiring a phase of inflationary expansion. We highlight the key points of this mechanism, and discuss cosmological backgrounds in which this scenario can be realized. The spectrum of cosmo-logical perturbations has a small red tilt (like in scalar field-driven inflation) but (unlike in inflation) there is a small blue tilt of the spectrum of gravitational waves.

This paper presents the science potential of a deep ocean antineutrino observatory being developed at Hawaii. The observatory design allows for relocation from one site to another. Positioning the observatory 60 km distant from a nuclear reactor complex enables precision measurement of neutrino mixing parameters, leading to a determination of neutrino mass hierarchy and θ₁₃. At a mid-Pacific location the observatory measures the flux and ratio of uranium and thorium neutrinos from earth's mantle and performs a sensitive search for a hypothetical natural fission reactor in earth's core. A subsequent deployment at another mid-ocean location would test lateral heterogeneity of uranium and thorium in earth's mantle.

This paper describes the status of four CMB cosmology experiments which are currently being developed by the Berkeley group. These include the APEXSZ and South Pole Telescope searches for clusters of galaxies using the Sunyaev-Zeldovich effect and the Polar Bear and EBEX CMB polarization anisotropy experiments. These experiments exploit new detector technologies with Superconducting TES bolometers and frequency domain output multiplexing, which has been developed at Berkeley.

As a huge amount of high-resolution data made by future high-sensitivity CMB experiments comes along, it is timely to study some important issues such as asymmetric beam effects and the mixing and separation of the E-mode and B-mode polarization in order to make efficient and unbiased estimation of the CMB anisotropy power spectra.

We present an inflation model which realizes density fluctuations with a negative running spectral index large enough as inferred by WMAP observation. In this model two different stages of inflation occur successively in the observable regime. As a result of numerical investigation, we find that the fluctuations generated in the late first inflationary stage are enhanced to the level significant amount of primordial black holes could be produced due to parametric resonance and that it is stretched to a cosmological scale in the second inflation.

The recent three-year WMAP data selects large-field models with certain power-law potentials and small-field models for all power-law potentials as consistent inflation models. We study the large-field and small-field inflation model with a quadratic and a quartic potential within the framework of quantum field theory in an expanding Friedmann-Robertson-Walker universe. We find that quantum fluctuations in the small-field model lead to a significant contribution to the effective potential and may have non-negligible effects on the slow-roll parameters predicted by classical theory.

We have produced a cleaned map of the WMAP three-year data using an improved version of an internal linear combination (ILC) method to subtract the Galactic foreground emission. We divide the whole sky into hundreds of pixel groups with similar foreground spectral indices over a range of WMAP frequencies, apply the ILC for each group, and obtain a CMB map with foreground emission effectively reduced. With the resulting foreground-reduced ILC map, we have investigated the known anomalies in CMB maps at large scales, and confirmed that the quadrupole power is low and the quadrupole and the octopole are strongly aligned and are planar. Although our estimates are consistent with the previous measurements, ILC simulation implies that the observed low quadrupole power and the alignment between the quadrupole and the octopole are marginally statistically significant, and the observed planarity is not statistically significant.

To clarify the issue of obtaining the scale invariant CMB spectrum in bouncing cosmology, we examine the matching condition between the metric perturbations before and after the bounce. We prove a no-go theorem: independent of the details of the matching condition, a scale invariant spectrum is impossible as long as the local causality condition is satisfied. In our framework, it is easy to show that a violation of local causality around the bounce is needed in order to give a scale invariant spectrum. We study a specific scenario of this possibility by considering a nonlocal effective theory inspired by noncommutative geometry around the bounce and show that a scale invariant spectrum is possible.

We propose that cosmological density perturbation may originate from passive fluctuations of the inflaton, which are induced by colored quantum noise due to the coupling of the inflaton to the quantum environment. At small scales, the fluctuations grow with time to become nearly scale-invariant. However, the larger-scale modes cross out the horizon earlier and do not have enough time to grow, thus resulting in a suppression of the density perturbation. This may explain the observed low quadrupole in the CMB anisotropy data and potentially unveil the initial time of inflation. We also discuss the implications to the running spectral index and the non-Gaussianity of the primordial density perturbation.

Coupling between quintessence and pseudoscalar of electromagnetism induces the rotation of the polarization plane of Cosmic Microwave Background(CMB). This rotation mixes the power between E and B modes and generates parity-violating TB and EB modes. Given the potential of a quintessence model, we present the full set of CMB power spectra for temperature and polarization anisotropies. These power spectra can be used to constrain the coupling and quintessence model.

Our universe might be a domain wall or kink carrying localized standard model fields embedded in a 4 + 1-dimensional space. I report on some initial studies of the cosmology of such a model, focusing on the relatively simple de Sitter (dS) and Anti-de Sitter (AdS) cases for the effective 3 + 1-dimensional FRW metric. Fermion localization to the AdS₄ and dS₄ domain walls is briefly discussed.

In this talk, we take the wisdom that the cosmological QCD phase transition, which happened at a time between 10⁻⁵ sec and 10⁻⁴ sec or at the temperature of about 150 MeV and accounts for confinement of quarks and gluons to within hadrons, would be of first order, i.e., would release latent "heat" or latent energy. I wish to base on two important points, i.e. (1) that we have 25% dark matter in the present Universe, and (2) that when the early universe underwent the cosmological QCD phase transition it released 1.02 × 10gm/cm³ in latent energy huge compared to 5.88 × 10⁹ gm/cm³ radiation (photon) energy, to deduce that the two numbers are in fact closely related. It is sufficient to approximate the true QCD vacuum as one of degenerate θ-vacua and can be modelled effectively via a complex scalar field with spontaneous symmetry breaking. We examine how "pasted" or "patched" domain walls are formed, how such walls evolve in the long run, and we believe that the majority of dark matter could be accounted for in terms of such domain-wall structure and its remnants. The latent energy released due to the conversion of the false vacua to the true vacua, in the form of "pasted" or "patched" domain walls at first and their evolved objects, make it obsolete the "radiation-dominated" epoch or later on the "matter-dominated" epoch.

We study a class of generalized inflation models in which the inflaton is coupled to the Ricci scalar by a general f(φ, R) term. The scalar power spectrum, the spectral index, the running of the spectral index, the tensor mode spectrum and a new consistency relation of the model are calculated.

Recently it was suggested that the dark energy maybe related to the well-known hierarchy between the Planck scale (~ 10¹⁹GeV) and the TeV scale. The same brane-world setup to address this hierarchy problem may also in principle address the smallness problem of dark energy. Specifically, the Planck-SM hierarchy ratio was viewed as a quantum gravity-related, dimensionless fine structure constant where various physical energy scales in the system are associated with the Planck mass through different powers of the 'gravity fine structure constant'. In this paper we provide a toy model based on the Randall-Sundrum geometry where SUSY-breaking is induced by the coupling between a SUSY-breaking Higgs field on the brane and the KK gravitinos. We show that the associated Casimir energy density indeed conforms with the dark energy scale.

Recent astrophysical observations of quasar absorption systems indicate that the fine structure constant α and the proton-electron mass ratio μ may have evolved through the history of the universe. Motivated by these observations, we consider the cosmological evolution of a quintessence-like scalar field ϕ coupled to gauge fields and matter which leads to effective modifications of the coupling constants and particle masses over time. We show that a class of models where the scalar field potential V(ϕ) and the couplings to matter B(ϕ) admit common extremum in ϕ naturally explains constraints on variations of both the fine structure constant and the proton-electron mass ratio.

Regarding the possible effects of inhomogeneity on the cosmic evolution, two of the essential issues are discussed. The most fundamental one is whether the Friedmann-Lemaitre-Robertson-Walker cosmology is a good approximation for describing our universe. The other is whether the accelerating expansion can be driven by the inhomogeneity of the universe.

Recent spectroscopic observations of metal poor stars have indicated that both ⁷Li and ⁶Li have abundance plateaus as a function of the metallicity. Abundances of ⁷Li are about a factor three lower than the primordial abundance predicted by standard big-bang nucleosynthesis (SBBN), and ⁶Li abundances are ~ 1/20 of ⁷Li, whereas SBBN predicts negligible amounts of ⁶Li compared to the detected level. These discrepancies suggest that ⁶Li has another cosmological or Galactic origin. Furthermore, it appear that ⁷Li (and also ⁶Li) has been depleted from its primordial abundance by some post-BBN processes. We study the possibility that the radiative decay of long-lived particles has affected the cosmological lithium abundances in reality. We calculate the non-thermal nucleosynthesis associated with the radiative decay, and explore the allowed region of the parameters specifying the properties of long-lived particles. We also impose constraints from observations of the CMB energy spectrum. It is found that non-thermal nucleosynthesis could produces ⁶Li at the level detected in metal poor halo stars (MPHSs), when the lifetime of the unstable particles is of the order ~ 10⁸ − 10¹²s depending on their initial abundance. We conclude that a combination of two different processes could explain the lithium isotopic abundances in MPHSs. First, a non-thermal cosmological nucleosynthesis associated with the radiative decay of unstable particles; and second, about the same degree of stellar depletion of both primordial lithium isotopic abundances. If MPHSs experience ⁶Li depletion of factor much greater than ~ 3, the simple radiative decay process can not be the cause of large ⁶Li abundances in MPHSs.

We show that an unification of quantum mechanics and general relativity implies that there is a fundamental length in Nature in the sense that no operational procedure would be able to measure distances shorter than the Planck length. Furthermore we give an explicit realization of an old proposal by Anderson and Finkelstein who argued that a fundamental length in nature implies unimodular gravity. Finally, using hand waving arguments we show that a minimal length might be related to the cosmological constant which, if this scenario is realized, is time dependent.

We investigated a simple D-term inflation with taking account of higher order corrections in the Kähler potential. These terms may solve the cosmic string problem in D-term inflation model. The mass per unit length of cosmic strings formed after inflation can be suppressed enough. In addition, the change of the potential slope leads simultaneously a more tilted scalar spectral index n_s ≃ 0.96 – 0.97 than that in the model without these corrections.

First we briefly review our covariant Hamiltonian approach to quasi-local energy, noting that the Hamiltonian-boundary-term quasi-local energy expressions depend on the chosen boundary conditions and reference configuration. Then we present the quasi-local energy values resulting from the formalism applied to homogeneous Bianchi cosmologies. Finally we consider the quasi-local energies of the FRW cosmologies. Our results do not agree with certain widely accepted quasi-local criteria.

We present a new class of time-dependent solution to the ten-dimensional type 0 effective action. Given a generic potential of tachyon field, there exist phases where tachyon is either frozen at local extremals or free to propagate along flat directions. In the latter phase, a cosmology model is proposed where the tachyon plays the role of time.

For the Poincaré gauge theory of gravity we consider the dynamical scalar torsion mode in a cosmological context. We explore in particular the possibility of using dynamical torsion to explain the current state of the accelerating Universe. With certain suitable sets of chosen parameters, this model can give a (qualitatively) proper description of the current universe without a cosmological constant, and the universe described is oscillating with a period of the Hubble time.

We derive the energy asymmetry given the proto-neutron star during the time when the neutrino sphere is near the surface of the proto-neutron star, using the modified URCA process. The electrons produced with the anti-neutrinos are in Landau levels due to the strong magnetic field, and this leads to asymmetry in the neutrino momentum, and a pulsar kick. Our main prediction is that the large pulsar kicks start at about 10 s and last for about 10 s, with the corresponding neutrinos correlated in the direction of the magnetic field.

We calculate the effective potential of a strong magnetic field induced by fermions with anomalous magnetic moments which couple to the electromagnetic field in the form of the Pauli interaction. For a uniform magnetic field, we find the explicit form of the effective potential. It is found that the non-vanishing imaginary part develops for a magnetic field stronger than a critical field and has a quartic form which is quite different from the exponential form of the Schwinger process. We also consider a linear magnetic field configuration as an example of inhomogeneous magnetic fields. We find that the imaginary part of the effective potential is nonzero even below the critical field and shows an exponentially decreasing behavior with respect to the inverse of the magnetic field gradient, which is the non-perturbative characteristics analogous to the Schwinger process. These results imply the instability of the strong magnetic field to produce fermion pairs as a purely magnetic effect. The possible applications to the astrophysical phenomena with strong magnetic field are also discussed.

We investigate a generation of magnetic fields from cosmological density perturbations. In the primordial plasma before cosmological recombination, all of the materials except dark matter in the universe exist in the form of photons, electrons, and protons (and a small number of light elements). Due to the different scattering nature of photons off electrons and protons, electric currents and electric fields are inevitably induced, and thus magnetic fields are generated. We numerically obtain the power spectrum of magnetic fields over a wide range of scales, from k ~ 10⁻⁵Mpc⁻¹ to k ~ 10⁹Mpc⁻¹. Implications of these cosmologically generated magnetic fields are discussed.

We present results from a weak lensing analysis of the galaxy cluster A1689 (z = 0.183) based on deep wide-field imaging data taken with Suprime-Cam on Subaru telescope. A maximum entropy method has been used to reconstruct directly the projected mass distribution of A1689 from combined lensing distortion and magnification measurements of red background galaxies. The resulting mass distribution is clearly concentrated around the cD galaxy, and mass and light in the cluster are similarly distributed in terms of shape and orientation. The azimuthally-averaged mass profile from the two-dimensional reconstruction is in good agreement with the earlier results from the Subaru one-dimensional analysis of the weak lensing data, supporting the assumption of quasi-circular symmetry in the projected mass distribution of the cluster.

Present experimental data from neutrino oscillations have provided much information about the neutrino mixing angles. Since neutrino oscillations only determine the mass squared differences , the absolute values for neutrino masses m_i, can not be determined using data just from oscillations. In this work we study implications on neutrino masses from a geometric mean mass relation which enables one to determined the absolute masses of the neutrinos. We find that the central values of the three neutrino masses and their 2σ errors to be m₁ = (1.58 ± 0.18)meV, m₂ = (9.04 ± 0.42)meV, and m₃ = (51.8 ± 3.5)meV. Implications for cosmological observation, beta decay and neutrinoless double beta decays are discussed.

Light dark matter aims at explaining the 511 keV γ-ray line emission from the galactic bulge as well as cold dark matter in our universe. The former is achieved via the annihilations or decays of light dark matter particles, which implies interesting observational consequences in addition to 511 keV γ-rays. We consider the axino in the 1 ~ 10 MeV mass range as the light dark matter particle and discuss the particle physics models for it, its cosmological production, and its decay arising from R-parity violation. For additional observational signals, we consider the connection to the neutrino data made by bilinear R-parity violations and the continuum γ-ray emission from light dark matter particles.

We study possible observational effects of scalar dark matter, the darkon D, in Higgs h and top quark t decay processes, h → DD and t → cDD in the minimal Standard Model (SM) and its two Higgs doublet model (THDM) extension supplemented with a SM singlet darkon scalar field D. We find that the darkon D can have a mass in the range of sub-GeV to several tens of GeV, interesting for LHC and ILC colliders, to produce the required dark matter relic density. In the SM with a darkon, t → cDD only occurs at loop level giving a very small rate, while the rate for Higgs decay h → DD can be large. In THDM III with a darkon, where tree level flavor changing neutral current (FCNC) interaction exists, a sizable rate for t → cDD is also possible.

We present cosmological perturbation theory in neutrino probe interacting dark-energy models, and calculate cosmic microwave background anisotropies and matter power spectrum. In these models, the evolution of the mass of neutrinos is determined by the quintessence scalar field, which is responsible for the cosmic acceleration today. We consider several types of scalar field potentials and put constraints on the coupling parameter between neutrinos and dark energy. Assuming the flatness of the universe, the constraint we can derive from the current observation is Σ m_ν < 0.87eV at the 95 % confidence level for the sum over three species of neutrinos.

A modern effective field theory is exploited to pin down accurately the flux S factors for the pp and hep processes in the Sun. The technique used is to combine the high accuracy established in few-nucleon systems of the "standard nuclear physics approach" (SNPA) and the systematic power counting of chiral perturbation theory (ChPT) into a consistent effective field theory framework. Using highly accurate wave functions obtained in the SNPA and working to N³LO in the chiral counting for the current, we make totally parameter-free and error-controlled predictions for the pp and hep processes in the Sun. We also discuss the convergence with respect to chiral expansion.

We briefly review neutrino properties, with emphasis on neutrino oscillations. We then present a status report on the proposed India-based Neutrino Observatory (INO). We focus on the physics studies possible with an iron calorimeter detector (ICAL) and the logistics of constructing this detector at INO. Such a detector would study atmospheric neutrinos in the first phase with the possibility of acting as a far-end detector of a future neutrino factory or beta beam. This talk was given at the Cosmology and Particle Astrophysics (CosPA) conference at Taipei, in Nov 2006.