Massive Potentials Research Articles

Constraints on Dirac-Born-Infeld type dark energy models from varying alpha

We study the variation of the effective fine-structure constant alpha for Dirac-Born-Infeld (DBI) type dark energy models. The DBI action based on string theory naturally gives rise to a coupling between gauge fields and a scalar field responsible for accelerated expansion of the universe. This leads to the change of alpha due to a dynamical evolution of the scalar field, which can be compatible with the recently observed cosmological data around the redshift $\stackrel{\texttildelow{}}{z}\ensuremath{\lesssim}3$. We place constraints on several different DBI models including exponential, inverse power-law and rolling massive scalar potentials. We find that these models can satisfy the varying alpha constraint provided that mass scales of the potentials are fine-tuned. When we adopt the mass scales which are motivated by string theory, both exponential and inverse power-law potentials give unacceptably large change of alpha, thus ruled out from observations. On the other hand the rolling massive scalar potential is compatible with the observationally allowed variation of alpha. Therefore the information of varying alpha provides a powerful way to distinguish between a number of string-inspired DBI dark energy models.

Simulated Melting Curve of NaCl up to 200 kbar

The melting curve of NaCl is studied up to 200 kbar by means of theshell-model molecular dynamics method, using massive shell coreinteraction potentials. The model for the interatomic interaction isshown to produce reasonable results at a wide range of pressures inbulk transitions. The pressure dependence of the melting curve of NaClwas calculated and the result was modified on the assumption ofoverheating due to the small system size and small time scalesimulation. The final result is in good agreement with the correctedexperimental values, accounting for melting mechanisms such as surfaceheating or superheating. Therefore, it is believed that bulk transitionsimulation at constant pressure indeed provides a useful tool forstudying the melting transition.

The D8-brane tied up: string and brane solutions in massive type IIA supergravity

We present two new solutions of Romans' massive type IIA supergravity characterized by the two non-trivial massive potentials of Romans' theory: the NSNS 2-form and the RR 7-form. They can be interpreted respectively as the intersection of a fundamental string and a D8-brane over a D0-brane and the intersection of a D6-brane with a D8-brane over a NSNS5-brane. The D8-brane manifests itself through the mass parameter and in the massless limit one recovers the standard fundamental string and D6-brane solutions. Although these solutions do not have the usual form for BPS bound states at threshold and each of them involves 3 objects, both of them preserve 1 4 of the supersymmetries.

A new massive type IIA supergravity from compactification

We consider the most general form for eleven dimensional supersymmetry compatible with on-shell superfields. This allows for the introduction of a conformal Spin(1,10) connection. In eleven dimensional Minkowski space this modification is trivial and can be removed by a field redefinition, however, upon compactification on S^1 it is possible to introduce a non-trivial `Wilson line'. The resulting ten dimensional supergravity has massive 1-form and 3-form potentials and a cosmological constant. This theory does not possess a supersymmetric eightbrane soliton but it does admit a supersymmetric non-static cosmological solution.

TWISTORS IN CONFORMALLY FLAT EINSTEIN FOUR-MANIFOLDS

This paper studies the two-component spinor form of massive spin-[Formula: see text] potentials in conformally flat Einstein four-manifolds. Following earlier work in the literature, a nonvanishing cosmological constant makes it necessary to introduce a supercovariant derivative operator. The analysis of supergauge transformations of primary and secondary potentials for spin-[Formula: see text] shows that the gauge freedom for massive spin-[Formula: see text] potentials is generated by solutions of the supertwistor equations. The supercovariant form of a partial connection on a nonlinear bundle is then obtained, and the basic equation of massive secondary potentials is shown to be the integrability condition on super β-surfaces of a differential operator on a vector bundle of rank 3. Moreover, in the presence of boundaries, a simple algebraic relation among some spinor fields is found to ensure the gauge invariance of locally supersymmetric boundary conditions relevant for quantum cosmology and supergravity.

Lorentz invariance, approach to helicity, and gauge transformations for Spin-1

Spin-1 fields are constructed automatically using the regular representation of the three-dimensional complex orthogonal group and the group's isomorphism with the Lorentz group. The fields and potentials are examined as one lets their mass go to zero. Going to masslessness after the differentiation of potentials results in a consistent formulation of the fields. The behavior of the massive and massless potentials under rotations in the particle frame is examined. The loss of global degrees of freedom as one goes from one to the other is made up by the appearance of gradient terms.