We consider a modified gravity plus single scalar-field model, where the scalar Lagrangian couples symmetrically both to standard Riemannian volume-form (spacetime integration measure density) given by square root of determinant metric, as well another non-Riemannian in terms an auxiliary maximal-rank antisymmetric tensor gauge field. As shown previous paper, pertinent dynamics provides exact unified description dark energy via dynamical generation cosmological constant, and matter "dust"...

We show that dark energy and matter can be described simultaneously by ordinary Einstein gravity interacting with a single scalar field provided the Lagrangian couples in symmetric fashion to two different spacetime volume forms (covariant integration measure densities) on manifold – one standard Riemannian given $$\sqrt{-g}$$ (square root of determinant pertinent metric) another non-Riemannian form independent metric, defined terms an auxiliary antisymmetric tensor gauge maximal rank....

This paper provides a systematic description of the interplay between specific class reductions denoted as \cKPrm ($r,m \geq 1$) primary continuum integrable system -- Kadomtsev-Petviashvili ({\sf KP}) hierarchy and discrete multi-matrix models. The relevant structure is generalization familiar $r$-reduction full {\sf KP} to $SL(r)$ generalized KdV ${\sf cKP}_{r,0}$. important feature hierarchies presence symmetry generated by successive Darboux-B\"{a}cklund (DB) transformations. allows for...

We study in some detail the properties of a previously proposed new class string and brane models whose world-sheet (world-volume) actions are built with modified reparametrization-invariant measure integration which do not contain any ad hoc dimensionful parameters. The ratio standard Riemannian densities plays role dynamically generated or tension. latter is identified as (the magnitude of) an effective (non-Abelian) electric field strength on world-volume obeying Gauss-law constraint. As...

We propose a new class of gravity-matter-gauge theories in terms two different non-Riemannian volume-forms independent the Riemannian metric. The nonlinear gauge field system contains square-root $\sqrt{-F^2}$ standard Maxwell Lagrangian which is known to describe charge confinement flat spacetime. In physical Einstein frame we obtain an effective "k-essence" type with quadratic dependence on scalar "dilaton" kinetic term X, remarkable potential possessing infinitely large regions as well...

The Einstein–Rosen “bridge” wormhole solution proposed in the classic paper (Einstein and Rosen (1935) [1]) does not satisfy vacuum Einstein equations at throat. We show that fully consistent formulation of original requires solving bulk D=4 gravity coupled to a lightlike brane with well-defined world-volume action. non-vanishing contribution right-hand side throat matches precisely surface stress–energy tensor which automatically occupies (“horizon straddling”) — feature triggered by dynamics.

Lightlike p-branes (LL-branes) with dynamical (variable) tension allow simple and elegant Polyakov-type dual to it Nambu–Goto-like worldvolume action formulations. Here we first briefly describe the dynamics of LL-branes as test objects in various physically interesting gravitational backgrounds black hole type, including rotating ones. Next show that are appropriate sources provide proper matter energy–momentum tensors Einstein equations motion needed generate traversable wormhole...

We present a qualitatively new mechanism for dynamical spontaneous breakdown of supersymmetry. Specifically, we construct modified formulation standard minimal N=1 supergravity. The modification is based on an idea worked out in detail previous publications by some us, where proposed (non-supersymmetric) gravity theories employing alternative volume form (volume element, or generally-covariant integration measure) the pertinent Lagrangian action, defined terms auxiliary (pure-gauge) fields...

We propose a new class of gravity-matter models defined in terms two independent non-Riemannian volume forms (alternative generally covariant integration measure densities) on the spacetime manifold. For matter we choose appropriate scalar field potentials exponential form so that full system is invariant under global Weyl-scale symmetry. Solution pertinent equations motion produce dimensionful constants which spontaneously break invariance. In resulting effective Einstein-frame obtain an...

We describe a new type of gravity-matter models where gravity couples in non-conventional way to two distinct scalar fields providing unified Lagrangian action principle description of: (a) the evolution both "early" and "late" Universe - by "inflaton" field; (b) dark energy matter as manifestation single material entity "darkon" field. The essential non-standard feature our is employing formalism non-Riemannian space-time volume forms alternative generally covariant integration measure...

We propose a simple modified gravity model without any initial matter fields in terms of several alternative non-Riemannian spacetime volume elements within the metric (second order) formalism. show how volume-elements, when passing to physical Einstein frame, create canonical scalar field and produce dynamically non-trivial inflationary-type potential for latter with large flat region stable low-lying minimum. study evolution cosmological solutions from point view theory dynamical systems....

We consider a nonstandard model of gravity coupled to neutral scalar “inflaton” as well [Formula: see text] iso-doublet with positive mass squared and without self-interaction, gauge fields. The principal new ingredient is employing two alternative non-Riemannian spacetime volume-forms (covariant integration measure densities) independent the metric. latter have remarkable impact — although not introducing any additional propagating degrees freedom, their dynamics triggers series important...

We describe two interesting effects in wormhole physics. First, we find that a genuinely charged matter source may appear neutral to an external observer - phenomenon opposite the famous Misner-Wheeler "charge without charge" effect. This takes place when coupling bulk gravity/nonlinear-gauge-field system lightlike brane as source. The "charge-hiding" effect occurs solution which connects non-compact "universe", comprising exterior region of Schwarzschild-(anti-)de-Sitter (SdS) or purely...