We reexamine the transition magnetic moment solution to the solar neutrino problem. We argue that the absence of large time variations in the Super-Kamiokande rate provides strong evidence against spin-flavor flip in the solar convective zone. Spin-flavor flip could, however, occur in the primordial magnetic field in the radiative zone. We compute the longest lived toroidal mode for this field and show that spin-flavor flip in the radiative zone can account for all available solar data.Comment: 6 pages, 5 figures, version accepted for publication in Astroparticle Physic

The possibility that the energy density of the Universe is dominated by a network of low-tension domain walls provides an alternative to the commonly discussed cosmological constant and scalar-field quintessence models of dark energy. We quantify the lower bound on the number density of the domain walls that follows from the observed near-isotropy of the cosmic microwave background radiation. This bound can be satisfied by a strongly frustrated domain wall network. No fine-tuning of the parameters of the underlying field theory model is required. We briefly outline the observational consequences of this model.

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We explore the sensitivity of massive stars to neutrino magnetic moments. We find that the additional cooling due to the neutrino magnetic moments bring about qualitative changes to the structure and evolution of stars in the mass window 7 M ⊙ M 18 M ⊙ , rather than simply changing the time scales for the burning. We describe some of the consequences of this modified evolution: the shifts in the threshold masses for creating core-collapse supernovae and oxygen-neon-magnesium white dwarfs and the appearance of a new type of supernova in which a partial carbon-oxygen core explodes within a massive star. The resulting sensitivity to the magnetic moment is at the level of (2 − 4) × 10 −11 µ B .

We discuss bounds on the strength of the magnetic fields that could be buried in the radiative zone of the Sun. The field profiles and decay times are computed for all axisymmetric toroidal ohmic decay eigenmodes with lifetimes exceeding the age of the Sun. The measurements of the solar oblateness yield a bound of P7 MG on the strength of the field. A comparable bound is expected to come from the analysis of the splitting of the solar oscillation frequencies. The theoretical analysis of the double diffusive instability also yields a similar bound. The oblateness measurements at their present level of sensitivity are therefore not expected to measure a toroidal field contribution.

We reexamine the conventional physical description of the neutrino evolution inside the Sun. We point out that the traditional resonance condition has physical meaning only in the limit of small values of the neutrino mixing angle, θ ≪ 1. For large values of θ, the resonance condition specifies neither the point of the maximal violation of adiabaticity in the nonadiabatic case, nor the point where the flavor conversion occurs at the maximal rate in the adiabatic case. The corresponding correct conditions, valid for all values of θ including θ > π/4, are presented. An adiabaticity condition valid for all values of θ is also described. The results of accurate numerical computations of the level jumping probability in the Sun are presented. These calculations cover a wide range of ∆m 2 , from the vacuum oscillation region to the region where the standard exponential approximation is good. A convenient empirical parametrization of these results in terms of elementary functions is given. The matter effects in the socalled "quasi-vacuum oscillation regime" are discussed. Finally, it is shown how the known analytical results for the exponential,

We determine the sensitivity of the KamLAND and Borexino experiments to the neutrino regeneration effect in the Earth as a function of ∆m 2 and θ, using realistic numbers for the signal and background rates. We compare the results obtained with the χ 2 method with those obtained from the conventional day-night asymmetry analysis. We also investigate how well one should be able to measure the neutrino oscillation parameters if a large day-night asymmetry is observed, taking the LOW solution as an example. We present an enlarged parameter space, which contains mixing angles greater than π/4 where the heavy mass eigenstate is predominantly ν e , and determine the electron neutrino survival probability for this traditionally neglected scenario. We emphasize that this portion of the parameter space yields different physics results when dealing with the MSW solutions to the solar neutrino puzzle and should not be neglected.

Unparticle behavior is shown to be realized in the Randall-Sundrum 2 (RS 2) and the Lykken-Randall (LR) brane scenarios when brane-localized Standard Model currents are coupled to a massive vector field living in the five-dimensional warped background of the RS 2 model. By the AdS/CFT dictionary these backgrounds exhibit certain properties of the unparticle CFT at large N c and strong 't Hooft coupling. Within the RS 2 model we also examine and contrast in detail the scalar and vector position-space correlators at intermediate and large distances. Unitarity of brane-to-brane scattering amplitudes is seen to imply a necessary and sufficient condition on the positivity of the bulk mass, which leads to the well-known unitarity bound on vector operators in a CFT.We propose here that the models based on warped extra spacetime dimensions, specifically the famous Randall-Sundrum 2 (RS 2, [23]) and Lykken-Randall (LR, [24]) brane constructions, with the SM fields on the brane and new fields in the bulk in fact realize unparticle physics. We will show, using a simple example of the bulk vector field, that both of these models reproduce all the requisite properties listed above.Right at the outset, we would like to make the following two comments. Firstly, ours is not the first assertion that holographic 1 constructions could realize unparticle physics [6,8,13,25]. The issue is whether such constructions yield theories that are merely similar to unparticle physics ("unparticle-like"), or are genuine realizations of it. At the moment, there does not seem to be a consensus in the literature on this point. To the best of our knowledge, ours is the first systematic analysis that establishes all of the unparticle properties in these setups.Secondly, these holographic models are different from the framework for the unparticle scenario originally envisioned in [1,2]. The latter involves a purely four-dimensional Banks-Zaks (BZ) [26] sector coupled to the SM by messenger fields at a high mass scale, M U . If below M U the BZ couplings flow into an infrared fixed point -at the "transmutation" scale Λ U ≪ M U -the hidden CFT sector is obtained 2 . It is important to stress that, conceptually, there is nothing inherently superior or inferior about one framework versus another. In fact, they model the unparticle sector in different regimes. The BZ realization teaches us about the unparticle sector in the weak (perturbative) regime, and can be used quite effectively, as demonstrated by GIR. Instead, the RS 2/LR realizations allow us to extend their results to strong coupling (large N c ). We will return to this important point at the end of the paper.From the practical standpoint, the RS 2/LR constructions make it possible to study what would be a quantum behavior in the CFT sector with classical equations in the bulk. This makes many of the key unparticle effects, such as the contact terms, the production of unparticles, and the CFT unitarity bounds, particularly transparent and intuitive. It also allows us to easily go beyond simply ...