International Journal of Modern Physics A

The MINOS experiment uses the NuMI ν_μ beam to make precise measurements of neutrino flavor oscillations in the "atmospheric" neutrino sector. MINOS can also probe the yet-unknown neutrino mixing angle θ₁₃ by searching for a ν_e appearance signal in the ν_μ beam. This paper reviews the techniques developed for the first ν_e appearance analysis in MINOS.

We construct explicit integral relations between propagators of generalized Schrödinger equations that are linked by higher-order supersymmetry. Our results complement and extend the findings obtained in J. Phys. A40, 10557 (2007) for the conventional Schrödinger equation.

We study how the property of asymptotic helicity conservation (HCns), expected for any 2-to-2 process in the minimal supersymmetric model (MSSM), is realized in the processes gg →γγ, γZ, ZZ, W⁺W^-, at one-loop electroweak order and very high energies. The violation of this property for the same process in the standard model (SM) is also shown. This strengthens the claim that HCns is specific to the renormalizable SUSY model, and not generally valid in the SM. HCns strongly reduces the number of nonvanishing 2-to-2 amplitudes at asymptotic energies in the MSSM.

The A-term is included in the logarithmic quark sigma model, which is based on chiral symmetry and its spontaneous breaking. We investigate the consequences of this term and its relevance to baryon properties. The field equations have been solved in the mean-field approximation for the hedgehog baryon state. We found that including the A-term in the logarithmic quark model leads to lower energies of the nucleon and delta masses and reduces the values of the sigma commutator σ_πN(0), proton μ_p(N), and neutron μ_n(N) of the magnetic moments. This indicates that the inclusion of the A-term improves the calculated nucleon properties in comparison with previous work and other models.

It is shown how actions corresponding to antisymmetric non-Abelian tensorial gauge field theories of (p+1)-dimensional diffeomorphisms yield p-brane actions associated with their (p+1)-dimensional worldvolume evolution. We conclude with a discussion of how to obtain p-brane actions from the large N limit of covariant matrix models based on generalized hypermatrices. A deformation quantization of Nambu classical mechanics furnishing Nambu quantum mechanics by constructing the n-ary noncommutative product of n functions f₁ •f₂ • ⋯ •f_n, the n-ary version of the Moyal bracket, and the analog of the Weyl–Wigner–Groenowold–Moyal map among operators and c-functions remains an open problem. A solution to this problem will reveal important relations between the physics of p-branes and matrix models based on generalized hypermatrices in the large N limit.

Space–time singularities are studied in both the (D+d)-dimensional string theory and its D-dimensional effective theory, obtained by the Kaluza–Klein compactification. It is found that space–time singularities in the low dimensional effective theory may or may not remain after lifted to the (D+d)-dimensional string theory, depending on particular solutions. It is also found that there exist cases in which space–time singularities appearing in high/low dimensional space–times do not necessarily happen on the same surfaces.

Based on conformal invariance and using Dirac's six-cone formalism, a new conformally invariant physical field equation for de Sitter (dS) linear gravity has been obtained, which corresponds to one of the unitary irreducible representations of the dS group and is denoted by in the sense of discrete series. Using ambient space notations, it has been shown that the solution to this new field equation can be written as the multiplication of a generalized symmetric polarization tensor of rank 2 and a massless conformally coupled scalar field in dS space–time. The physical tensor two-point function has been calculated in terms of the conformally coupled scalar two-point function in the ambient space formalism. It has been expressed in terms of dS intrinsic coordinates from its ambient space counterpart, which is dS-invariant and free of any divergences.

Inspired by the holographic principle, we suggest that the density of dark energy is proportional to the spatial Ricci scalar curvature (SRDE). Such a model is phenomenologically viable. The best fit values of its parameters at 68% confidence level are found to be Ω_{m 0} = 0.259±0.016 and α = 0.261±0.0122, constrained from the Union+CFA3 sample of 397 SNIa and the BAO measurement. We find that the equation of state of SRDE crosses -1 at z ≃ -0.14. The present value of the deceleration parameter q(z) for SRDE is found to be q_{z = 0}~-0.85. The phase transition from deceleration to acceleration of the Universe for SRDE occurs at the redshift z_{q = 0}~0.4. After studying the perturbation of each component of the Universe, we show that the matter power spectra and cosmic microwave background temperature anisotropy are slightly affected by SRDE, compared with ΛCDM.

Abundances of primordial deuterium, and helium, Y_p, are examined by modifying the early universe expansion rate and hence the time–temperature relation, including a constant vacuum energy motivated by the cyclic scenario of brane cosmology. Enhancement of abundances with respect to standard BBN prediction is found. Rapid expansion leads to early freeze-out of weak interaction and hence to an enhanced neutron fraction at elevated freeze-out temperature, which in turn results in more helium. Nucleosynthesis at a much lower temperature (due to rapid expansion) faces a larger Coulomb barrier and leaves more deuterium behind, which is also implied by a lower baryon-to-photon ratio (η) as we increase the vacuum energy density. The change in the helium fraction agrees within orders of magnitudes with that found by the effect of more neutrino flavors on Y_p. Elevation of the neutron fraction at freeze-out is revealed by decrease in the neutron–proton mass difference (Q) from 1.293 MeV to 1.279 MeV, which is consistent with the study of the influence of extra dimension size on BBN. The lowest Q value corresponds to the highest vacuum energy and also to the largest size of the extra dimension. The upper limit on vacuum energy density is found by estimating the contribution from nonbaryonic dark matter by using X-ray emission from galaxy clusters and taking a flat spatial geometry, which is found to be the cosmological constant (Λ) observed today, so that the abundances do not run beyond the observational upper bounds. The allowed range of Ω_Λ, 0.786 ≤ Ω _Λ ≤ 0.844, makes Y_p and lie within the observational upper bounds, which yields a Big Bang equivalence of the Λ universe. This is expected to further motivate the cyclic scenario, which incorporates a small and constant vacuum energy density tied to spacetime.