Hyperfluid - a model of classical matter with hypermomentum

A variational theory of a continuous medium is developed the elements of which carry momentum and hypermomentum (hyperfluid). It is shown that the structure of the sources in metric-affine gravity is predetermined by the conservation identities and, when using the Weyssenhoff ansatz, these explicitly yield the hyperfluid currents.Comment: plain Tex, 11 pages, no figure

Exploring Important Protein Interactions in the Mammalian Diaphanous-related Formins: A Closer Look at the Relationship between the Intracellular Skeletal Network and a Single Amino Acid Residue

The Diaphanous-related formin protein family plays a key role in intracellular cytoskeletal regulation. Due to their farreaching importance, these proteins must be highly regulated themselves. With recent exploration of regulatory processes of mDia2, a formin protein found in mammals, the established mechanism of control appears to be more complex than previously thought. This project examines the possibility of phosphorylation at critical sites near the protein regions that regulate formin function. Here, we outline our initial screen for discovering these specific residues within mDia2 and their potential for phosphorylation using site-directed mutagenesis

On the derivation of the spacetime metric from linear electrodynamics

In the framework of metric-free electrodynamics, we start with a {\em linear} spacetime relation between the excitation 2-form $H = ({\cal D}, {\cal H})$ and the field strength 2-form $F = ({E,B})$. This linear relation is constrained by the so-called closure relation. We solve this system algebraically and extend a previous analysis such as to include also singular solutions. Using the recently derived fourth order {\em Fresnel} equation describing the propagation of electromagnetic waves in a general {\em linear} medium, we find that for all solutions the fourth order surface reduces to a light cone. Therefrom we derive the corresponding metric up to a conformal factor.Comment: 11 Pages, LaTeX, some typos corrected, one reference added. Version published in Physics Letters

On the triviality of certain non-Riemannian models of gravitation

We prove in the Tucker-Wang approach to non-Riemannian Gravity that a general homogeneous Lagrangian density in the general connection with order of homogeneity of at least two, gives no contribution to the generalised Einstein equations. Using this result other important cases are also considered.Comment: 12 pages, Latex, final version for Physics Letters

On the theory of the skewon field: From electrodynamics to gravity

The Maxwell equations expressed in terms of the excitation $\H=({\cal H}, {\cal D})$ and the field strength $F=(E,B)$ are metric-free and require an additional constitutive law in order to represent a complete set of field equations. In vacuum, we call this law the ``spacetime relation''. We assume it to be local and linear. Then $\H=\H(F)$ encompasses 36 permittivity/permeability functions characterizing the electromagnetic properties of the vacuum. These 36 functions can be grouped into 20+15+1 functions. Thereof, 20 functions finally yield the dilaton field and the metric of spacetime, 1 function represents the axion field, and 15 functions the (traceless) skewon field \notS_i{}^j (S slash), with $i,j=0,1,2,3$. The hypothesis of the existence of \notS_i{}^j was proposed by three of us in 2002. In this paper we discuss some of the properties of the skewon field, like its electromagnetic energy density, its possible coupling to Einstein-Cartan gravity, and its corresponding gravitational energy.Comment: latex-file, 15 pages, 1 figur

Modified coupling procedure for the Poincar\'e gauge theory of gravity

The minimal coupling procedure, which is employed in standard Yang-Mills theories, appears to be ambiguous in the case of gravity. We propose a slight modification of this procedure, which removes the ambiguity. Our modification justifies some earlier results concerning the consequences of the Poincar\'e gauge theory of gravity. In particular, the predictions of the Einstein-Cartan theory with fermionic matter are rendered unique.Comment: 4 page