Exterior Differential Forms Research Articles

К ПРОЕКТИВНО–ДИФФЕРЕНЦИАЛЬНОЙ ГЕОМЕТРИИ ПЯТИМЕРНЫХ КОМПЛЕКСОВ ДВУМЕРНЫХ ПЛОСКОСТЕЙ ПРОЕКТИВНОГО ПРОСТРАНСТВА P5

The article focuses on the differential geometry  of 5-dimensional complexes  C5 of 2-dimensional planes in the projective  space  P5 that contains a finite  number of developable surfaces. This article relates to researches on the projective differential geometry based on E. Cartan’s moving frame method and the method of exterior differential forms. These methods make it possible to study the differential geometry of submanifolds of different dimensions of a Grassmann manifold from a single viewpoint and also extend the results to wider classes of manifolds of multidimensional planes. In order to study such submanifolds, we apply the Grassmann mapping of the manifold  G(2, 5) onto the 9-dimensional algebraic manifold Ω(2, 5) of the space P19. The main task of the differential geometry of submanifolds of Grassmann manifolds is to carry out uniform classifications of various classes of such submanifolds, determine their structure and define the degree of the arbitrariness of their existence and also to research properties of submanifolds of various classes. Intersection of the algebraic manifold Ω(2, 5) with its tangent space TlΩ(2, 5) represents the Segre cone Cl(3, 3). This 5-dimensional cone carries two sets of plane 3-dimensional generatrices intersecting in straight lines. The projectivization PBl(2) of this cone is the Segre manifold Sl(2, 2). The Segre manifold Sl(2, 2) is invariant under projective transformations of P8 = PTlΩ(2, 5), which is the projectivization with center at the point l of the tangent space TlΩ(2, 5) to the algebraic manifold Ω(2, 5). The Segre manifold Sl(2, 2) is used for classification of the submanifolds of Grassmann manifold G(2, 5) under consideration, as well as for interpretation of their properties  in the projective algebraic manifold terms.  The classification  of submanifolds of the Grassmann manifold G(2, 5) is  based on  various  configurations of the plane PTlΩ(2, 5) and on the Segre manifold Sl(2, 2).  The goal of this article  is to prove geometrically the theorem for determination of the order of the Segre invariant manifold Sl(2, 2).

Simple supergravity pp-waves

Non-gauge generated exact solutions of simple supergravity field equations that describe pp-waves in Rosen coordinates are presented in the language of complex quaternion valued exterior differential forms.

Dark Range of ω In Brans-Dicke Gravity

The variational field equations of Brans-Dicke scalar-tensor theory of gravitation that is coupled to a mass-varying sterile neutrino field are presented in Riemannian and non-Riemannian setting in the language of exterior differential forms over four-dimensional spacetime. In a gravitational plane wave geometry in Rosen coordinates, with the scalar field set equal to a constant, the field equations admit ghost neutrino solutions. These correspond to Majorana spinor configurations for which the total neutrino stress-energy-momentum tensor vanishes. We show here that in the absence of a sterile neutrino in the gravitational wave geometry, there are scalar field configurations for which the total scalar field stress-energy-momentum tensor vanishes for negative values of the Brans-Dicke parameter —3/2 < ω < 0.

The Variational Field Equations of Cosmological Topologically Massive Supergravity

AbstractWe discuss the formulation of cosmological topologically massive (simple) supergravity theory in three‐dimensional Riemann‐Cartan space‐times. We use the language of exterior differential forms and the properties of Majorana spinors on 3‐dimensional space‐times to explicitly demonstrate the local supersymmetry of the action density involved. Exact coupled field equations that are complete in both of their bosonic and fermionic sectors are derived by a first order variational principle subject to a torsion‐constraint imposed by the method of Lagrange multipliers. Cotton and Cottino 2‐forms that are complete to all orders in the gravitino field are derived and their properties such as trace are investigated.

Electric charge screening by non-minimal couplings of electromagnetic fields to gravity

A case of non-minimal couplings between gravity and electromagnetic fields is presented. The field equations are worked out in the language of exterior differential forms. A class of exact charge screening solutions is given with a specific discussion on the polarisation and magnetisation of space-time. The consequences of non-minimal couplings to gravity are examined.

A nonminimally coupled, conformally extended Einstein-Maxwell theory of pp-waves

A nonminimal coupling of Weyl curvatures to electromagnetic fields is considered in Brans-Dicke-Maxwell theory. The gravitational field equations are formulated in a Riemannian spacetime where the spacetime torsion is constrained to zero by the method of Lagrange multipliers in the language of exterior differential forms. The significance and ramifications of nonminimal couplings to gravity are examined in a pp-wave spacetime.

Shape equations for two-dimensional manifolds with nonempty boundary based on a variational method

A smooth surface is considered which has a curved boundary. A system of exterior differential forms is introduced which describes the surface and boundary curves completely in the moving frame approach. A total free energy functional is defined based on these forms for which an equilibrium equation and boundary conditions of the surface are derived by calculating the variation of the total free energy. These results can be applied to a surface with several freely exposed edges.

Gravitational plane waves in a non-Riemannian description of Brans–Dicke gravity

The gravitational field equations of Brans–Dicke theory are given in a 4-dimensional non-Riemannian space-time with torsion in the language of exterior differential forms A class of pp-wave metrics together with the Brans–Dicke scalar field are used to derive the autoparallel equations of motion for non-spinning test masses. These are compared with the geodesic equations of motion and the differences are pointed out. The effects of the gradient of the Brans–Dicke scalar on the geodesic deviation equations in this non-Riemannian setting are also discussed.

Connections between physics, mathematics, and deep learning.

Starting from Fermat's principle of least action, which governs classical and quantum mechanics and from the theory of exterior differential forms, which governs the geometry of curved manifolds, we show how to derive the equations governing neural networks in an intrinsic, coordinate-invariant way, where the loss function plays the role of the Hamiltonian. To be covariant, these equations imply a layer metric which is instrumental in pretraining and explains the role of conjugation when using complex numbers. The differential formalism clarifies the relation of the gradient descent optimizer with Aristotelian and Newtonian mechanics. The Bayesian paradigm is then analyzed as a renormalizable theory yielding a new derivation of the Bayesian information criterion. We hope that this formal presentation of the differential geometry of neural networks will encourage some physicists to dive into deep learning and, reciprocally, that the specialists of deep learning will better appreciate the close interconnection of their subject with the foundations of classical and quantum field theory.

Non-Riemannian description of Robinson–Trautman spacetimes in Brans–Dicke theory of gravity

The variational field equations of Brans–Dicke scalar-tensor theory of gravitation are given in a non-Riemannian setting in the language of exterior differential forms over four-dimensional spacetimes. A conformally rescaled Robinson–Trautman metric together with the Brans–Dicke scalar field are used to characterize algebraically special Robinson–Trautman spacetimes. All the relevant tensors are worked out in a complex null basis and given explicitly in an appendix for future reference. Some special families of solutions are also given and discussed.

Two Problems in the Theory Of Differential Equations

1) The differential equation considered in terms of exterior differential forms, as \'E.Cartan did, singles out a differential ideal in the supercommutative superalgebra of differential forms, hence an affine supervariety. In view of this observation, it is evident that every differential equation has a supersymmetry (perhaps trivial). Superymmetries of which (systems of) classical differential equations are missed yet? 2) Why criteria of formal integrability of differential equations are never used in practice?

Induced C*-Complexes in Metaplectic Geometry

For a symplectic manifold admitting a metaplectic structure and for a Kuiper map, we construct a complex of differential operators acting on exterior differential forms with values in the dual of the Kostant's symplectic spinor bundle. Defining a Hilbert $C^*$-structure on this bundle for a suitable $C^*$-algebra, we obtain an elliptic $C^*$-complex in the sense of Mishchenko--Fomenko. Its cohomology groups appear to be finitely generated projective Hilbert $C^*$-modules. The paper can serve as a guide for handling of differential complexes and PDEs on Hilbert bundles

On Connection between Second-Degree Exterior and Symmetric Derivations of Kähler Modules

Mathematical physics looks for ways to apply mathematical ideas to problems in physics. In differential forms, the tensor form is first defined, and the definitions of exterior and symmetric differential forms are made accordingly. For instance, M is an R-module, M ⊗ R M the tensor product of M with itself and H a submodule of M ⊗ R M generated by x ⊗ y − y ⊗ x , where x , y in M. Then, ∨ 2 ( M ) = M ⊗ R M / H is called the second symmetric power of M. A role of the exterior differential forms in field theory is related to the conservation laws for physical fields, etc. In this study, I present a new approach to emphasize the properties of second exterior and symmetric derivations on Kahler modules, and I find a connection between them. I constitute exact sequences of ∨ 2 ( Ω 1 ( S ) ) and Λ 2 ( Ω 1 ( S ) ) , and I describe and prove a new isomorphism in the following: Let S be an affine algebra presented by R / I , where R = k [ x 1 , … x s ] is a polynomial algebra and I = ( f 1 , … f m ) an ideal of R. Then, I have J 1 Ω 1 ( S ) ≃ Ω 1 ( S ) ⊕ ∨ 2 ( Ω 1 ( S ) ) ⊕ Λ 2 ( Ω 1 ( S ) .

Supersymmetric theory of stochastic ABC model

In this paper, we investigate numerically the stochastic ABC model, a toy model in the theory of astrophysical kinematic dynamos, within the recently proposed supersymmetric theory of stochastics (STS). STS characterizes stochastic differential equations (SDEs) by the spectrum of the stochastic evolution operator (SEO) on elements of the exterior algebra or differential forms over the system’s phase space, X. STS can thereby classify SDEs as chaotic or non-chaotic by identifying the phenomenon of stochastic chaos with the spontaneously broken topological supersymmetry that SEOs of all SDEs possess. We demonstrate the following three properties of the SEO, deduced previously analytically and from physical arguments: the SEO spectra for zeroth and top degree forms never break topological supersymmetry, all SDEs possess pseudo-time-reversal symmetry, and each de Rham cohomology class provides one supersymmetric eigenstate. Our results also suggest that the SEO spectra for forms of complementary degrees, i.e., k and dim X −k, may be isospectral.

Application of the moving frame method to deformed Willmore surfaces in space forms

Abstract The main goal of this paper is to use the theory of exterior differential forms in deriving variations of the deformed Willmore energy in space forms and study the minimizers of the deformed Willmore energy in space forms. We derive both first and second order variations of deformed Willmore energy in space forms explicitly using moving frame method. We prove that the second order variation of deformed Willmore energy depends on the intrinsic Laplace Beltrami operator, the sectional curvature and some special operators along with mean and Gauss curvatures of the surface embedded in space forms, while the first order variation depends on the extrinsic Laplace Beltrami operator.

EXTERIOR DIFFERENTIAL FORMS ON RIEMANNIAN SYMMETRIC SPACES

In the present paper we give a rough classification of exterior differential forms on a Riemannian manifold. We define conformal Killing, closed conformal Killing, coclosed conformal Killing and harmonic forms due to this classification and consider these forms on a Riemannian globally symmetric space and, in particular, on a rank-one Riemannian symmetric space. We prove vanishing theorems for conformal Killing L 2-forms on a Riemannian globally symmetric space of noncompact type. Namely, we prove that every closed or co-closed conformal Killing L 2-form is a parallel form on an arbitrary such manifold. If the volume of it is infinite, then every closed or co-closed conformal Killing L 2-form is identically zero. In addition, we prove vanishing theorems for harmonic forms on some Riemannian globally symmetric spaces of compact type. Namely, we prove that all harmonic one-formsvanish everywhere and every harmonic r -form  r  2 is parallel on an arbitrary such manifold. Our proofs are based on the Bochnertechnique and its generalized version that are most elegant and important analytical methods in differential geometry “in the large”.

Differential form representation of stochastic electromagnetic fields

Abstract. In this work, we revisit the theory of stochastic electromagnetic fields using exterior differential forms. We present a short overview as well as a brief introduction to the application of differential forms in electromagnetic theory. Within the framework of exterior calculus we derive equations for the second order moments, describing stochastic electromagnetic fields. Since the resulting objects are continuous quantities in space, a discretization scheme based on the Method of Moments (MoM) is introduced for numerical treatment. The MoM is applied in such a way, that the notation of exterior calculus is maintained while we still arrive at the same set of algebraic equations as obtained for the case of formulating the theory using the traditional notation of vector calculus. We conclude with an analytic calculation of the radiated electric field of two Hertzian dipole, excited by uncorrelated random currents.

Construction of Hamiltonian and Nambu Forms for the Shallow Water Equations

A systematic method to derive the Hamiltonian and Nambu form for the shallow water equations using the conservation for energy and potential enstrophy is presented. Different mechanisms, such as vortical flows and emission of gravity waves, emerge from different conservation laws for total energy and potential enstrophy. The equations are constructed using exterior differential forms and self-adjoint operators, and result in the sum of two Nambu brackets—one for the vortical flow and one for the wave-mean flow interaction—and a Poisson bracket representing the interaction between divergence and geostrophic imbalance. The advantage of this approach is that the Hamiltonian and Nambu forms can here be written in a coordinate-independent form.

New improved massive gravity and three-dimensional spacetimes of constant curvature and constant torsion

We derive the field equations for topologically massive gravity coupled with the most general quadratic curvature terms using the language of exterior differential forms and a first order constrained variational principle. We find variational field equations both in the presence and absence of torsion. We then show that spaces of constant negative curvature (i.e. the anti de-Sitter space $AdS_3$) and constant torsion provide exact solutions.

New improved massive gravity

We derive the field equations for topologically massive gravity coupled with the most general quadratic curvature terms using the language of exterior differential forms and a first-order constrained variational principle. We find variational field equations both in the presence and absence of torsion. We then show that spaces of constant negative curvature (i.e. the anti de-Sitter space AdS3) and constant torsion provide exact solutions.