Submitted:
25 August 2025
Posted:
26 August 2025
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Abstract
Keywords:
1. Introduction: Metric and Nonmetric Finsler-Lagrange-Hamilton Geometric Flows, GR and MGTs
1.1. Historical Remarks on Finsler-like Relativistic Geometric Flow and Gravity Theories
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Prehistory and beginning of History (1854-1934): B. Riemann considered in his famous habilitation thesis ([27], 1854) the first example of nonlinear quadratic element where are coordinated on a base manifold V and are certain fibler/velocity like coordinates. Such an involving homogeneity conditions on y (when for ), was later called a Finsler metric, or (equivalently) a Finsler generating function. The Riemannian geometry was formulated and studied by using quadratic elements, for and a symmetric metric tensor That was the "prehistory" of Finsler geometry.− The "Finsler history" began in 1918 due to P. Finsler’s thesis [28], when the term "Finsler geometry" was introduced in E. Cartan’s first monograph on Finsler geometry from 1935 [29]. In that monograph (in coordinate form), the first examples of Finsler nonlinear, connection (N-connection) and linear distinguished connection (d-connection) were considered. Such values consist of two other cornerstone geometric objects (the first one is ). Mathematical details on so-called Riemann-Finsler geometry can be found in monographs [30,31,32]. We consider that E. Cartan’s contributions are also fundamental because without his first use of N- and d-connections and the concept of bundle space, Finsler geometric and physical models are incomplete for elaborating applications in physics. For our purposes to formulate and study relativistic Finsler generalizations of the Einstein gravity theory and to construct exact and parametric solutions in such theories, we follow the system of notations and conventions stated in [13,17,19].1
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Classical Geometric Ages (1935 - 1955): A series of fundamental geometric papers were published on so-called metric noncompatible Finsler geometry theories due to L. Berwald [33,34] and S. -S. Chern [35] and others. Such Finsler geometric models are different from the Finsler-Cartan theories and involve many conceptual and technical difficulties in elaborating Finsler modifications of GR and standard particle physics because of nontrivial nonmetricity fields, as we criticised in [17,19,36]. For instance, it is a problem how to define Finsler-spinors and Finsler-Dirac equations, conservation laws, and finding exact and parametric solutions of respective locally anisotropic modifications of the Einstein equations. In principle, a cure exists as in the case of metric-affine gravity theories formulated on (co) tangent Lorentz bundles following advanced geometric methods for constructing generic off-diagonal solutions as in [37]. For FLH MGTs, this is a task for a series of future works.− We also mention certain important works on the geometry of nonholonomic manifolds due to G. Vrǎnceanu and Z. Horak (1926-1955) [38,39,43]; and on the global theory of N-connections and Finsler geometry due to A. Kawaguchi (1937-1952) [40,41] and C. Ehresmann (1955) [42]. Summaries of results and detailed bibliography on the classical period of Finsler geometry and first applications can be found in [17,19,30,31,32].2 We can consider that all FLH models consist of particular examples of nonholonomic manifolds or (co) tangent bundle geometries defined by respective N-connection structures.
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Early Middle Ages (1950 - 1974): That was the beginning of research on applications of Finsler geometry methods in MGTs and geometric mechanics. For our purposes, we mention the first Finsler modification of the Einstein equations, when instead of the Levi-Civita (LC) connection ∇ the Cartan distinguished (d) connection was used (J. I. Horvath, 1950) [44]. We also cite the monograph [45], which contains a rigorous formulation of Finsler geometry as an example of (co) tangent bundle geometry. It is defined by Sasaki lifts of Hessians (vertical quadratic forms ), using N-connections, to total metrics on In our opinion, such constructions are very important because they result in well-defined geometrically complete d-metrics on (co) tangent Lorentz bundles and allow self-consistent extensions of metrics in GR.[-] Relativistic Lagrange mechanics as a generalized Finsler geometry without homogeneity conditions, on tangent Lorentz bundle. Another very important work was that due to J. Kern (1974) [46] who introduced the concept of Lagrange geometry with nonlinear quadratic element on a tangent bundle This provides an alternative geometrization of classical mechanics which is different from the standard approach to geometric mechanics (see, for instance, [47]). Finsler geometry is a particular example of homogeneous mechanics, when Such generalizations are very important because Finsler metrics with homogeneity conditions consists of a very special case, which is not motivated for general nonlinear interactions and MDRs in MGTs or GR.- Relativistic Hamilton mechanics as a cotangent Lorentz bundle model of generalized Finsler geometry and equivalent almost (symplectic) Kähler-Lagrange/ Hamilton.Using Legendre transforms, the concept of Hamilton geometry, with nonlinear quadratic elements , on cotangent bundle can be introduced. Such geometries can be constructed on Lorentz manifolds with nontrivial N-connection structures and described equivalently as almost (symplectic) Kähler-Lagrange/ Finsler (or Kähler-Hamilton/geometries, see [31,48,49,50]). Respectively, classical and quantum geometric techniques are important for the deformation quantization for such theories [17,51,52,53,54] (in chronological form, such developments are relevant to the research described for directions 6-7], see below).
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- Middle Ages (1959 - 1995): The period is characterized by many works on Finsler and other types of locally anisotropic field theories and gravity. It begins with the publication of the monograph [30] (H. Rund, 1959). It was translated into Russian by G. Asanov, who developed (together with his postgraduate students, during 1980-1990) in the former USSR some new directions with applications in physics of Finsler geometry [55,56,57]. M. Masumoto’s monograph [31] (1986) played a very important role in the elaboration of various variants of Finsler gravity theories and postulating certain versions of Finsler gravitational field equations [58,59,60,61,62,63,64,65]. At that time, certain methods of constructing solutions of locally anisotropic gravitational field equations were not formulated, but only certain post-Newtonian computations of possible Finsler anisotropy effects.
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- Dark non-standard Ages (1975 - 2011): It was an "Orthodox" period of GR and standard particle physics, when influential authors in gravity and QFT [66,67] concluded that Finsler theories with generic anisotropies had substantial restrictions by experimental and observational data. Their theoretical analysis had not involved nontrivial N-connection structures, which made those conclusions quite uncertain and ambiguous. Unfortunately, because of the mentioned works, tents of Finsler papers (including manuscripts by this author) were rejected from Phys. Rev. Lett. and Phys. Rev. D as "as unphysical". That situation was described in Appendix B of the preprint variant of [17], see also references therein. Nevertheless, many authors in the USA, Japan, Germany, UK, Canada, Greece, Russia, Poland, Romania, R. Moldova, etc., published in other mathematical and theoretical physics journals of number of papers on generalized Finsler gravity theories [17,68,69,70]. Here we note that important works (using the FLH geometric methods) were performed using nonholonomic fibered structures on Lorentz manifolds, in extra-dimension gravity, string theory, noncommutative Finsler gravity, etc. [71,72,73,74,75]. A series of important monographs on nonholonomic manifolds and generalized Finsler gravity and applications were published [19,50,62,64,76,77].
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Renaissance (1996 - 2011): The period is characterized by a new series of works on modified dispersion relations (MDRs) and local Lorentz invariance violations (LIVs) as attempts to solve certain important problems in QG, string theory and other MGTs [78,79,80]. For additional assumptions on nonholonomic geometric structures, various classes of such theories can be formulated as (generalized) Finsler geometries. This induced in the literature a non-correct opinion that Finsler gravity models are theories with local anisotropies determined by MDRs and LIVs [81,82,83,84].- Elaborating general methods for constructing exact and parametric solutions in FLH MGTs. As we mentioned above, FLH geometric and physical models can be formulated in general self-consistent forms on (co) tangent Lorentz bundles when the postulates of GR theory can be extended from similar ones with Lorentz manifolds [17,19,85]. Using nonholonomic methods as in Finsler geometry, redefined in canonical 2+2 variables on Lorentz spacetimes, we can construct new classes of off-diagonal exact and parametric solutions in GR and MGTs. Extending the constructions to higher dimensions involving nonholonomic dyadic decompositions and distortions of affine (linear) connections, the anholonomic frame and connection deformation method (AFCDM) was formulated [23,24,25,86,87,88]. Perhaps, this is the most general geometric and analytic method which allows us to decouple and integrate in certain general forms the gravitational and matter field equations in FLH and other types of MGTs, and GR, see recent reviews and results [13,17,26]. The ansatz for constructing such solutions is chosen as some generic off-diagonal metrics that depend on the type of distorting relations for connections, and on prescribed generating sources.-Problems with the definition of Finsler-spinors and Finsler-Dirac equations. Another fundamental problem for elaborating physically viable FLH is that of formulating Finsler generalizations of the concept of Clifford structures/ spinors adapted to N-connection structures. A related issue is that on how to formulate self-consistent variants of Finsler-Dirac equations, and (in general) to construct FLH modifications of the Einstein-Yang-Mills-Higgs-Dirac (EYMHD) equations. Such research programs were performed for metric compatible Finsler connections (during 1996 - 2012) in our works [19,62,64,89,90,91,92,93,94,95,96,97]. We criticized [17,19,36] the approaches for elaborating nonmetric Finsler gravity theories (involving Chern, Berwald and other type metric noncompatible Finsler connections). That was because of ambiguities with the definition of nonmetric versions of the Finsler-Dirac equations and with the formulation of conservation laws for nonmetric FLH deformed EYMHD systems. Such difficulties do not exist for the case of Finsler-Cartan geometry, and for FLH generalizations with metric-compatible Finsler connections. Recently, we discussed how to find a cure for nonmetric MGTs using physically important solutions as in [37,98]. One of the main purposes of this work is to show how the AFCDM can be applied both to metric and nonmetric FLHs modified Einstein equations with general generating sources. Proofs of the integrability of nonmetric FLH deformed EYMHD equations will be provided in our future works.- FLH MGTs and string gravity, locally anisotropic gauge gravity, supersymmetric and noncommutative Finsler models. The works [13,26,54,62,71,72,73,74,99,100] contain a series of original results on Finsler like (super) string and supergravity theories formulated for extra dimension coordinates being of velocity/ momentum type. The approach was developed for noncommutative Finsler gravity models, Finsler-Hořava-Lifshitz theories, almost Kaehler-Finsler models, deformation and gauge-like quantization of Finsler gauge gravity theories etc. [17,22,101,102,103,104,105]. The AFCDM was correspondingly generalized and applied to constructing physically important solutions in such FLH theories.- Metric and nonmetric nonholonomic and generalized Finsler geometric flows. This direction of our research (see reviews [13,37,106,107]) was inspired by G. Perelman’s preprint [108] on the entropy of Ricci flows and related proof of the Poincaré-Thurston conjecture, see mathematical methods in [109,110,111,112]. Formulatig Finsler generalizations (in a certain unified form of that conjecture) is not possible because of the various types of Finsler geometries. This is different from the case of Riemannian or Kähler geometry. Nevertheless, we can construct abstract geometric and N-adapted variational forms of FLH geometric flow models by using distortions of connections. The most important motivation to formulate such Finsler-like generalizations is that the concepts of G. Perelman W-entropy, and respective statistical and geometric thermodynamic variables, can be computed for any type of FLH geometries and MGTs defined by certain (generalized) Ricci scalar and Ricci tensors. This is enough for analyzing the thermodynamic properties of large classes of exact and parametric solutions in FLH gravity and geometric flow theories. In general, the off-diagonal solutions are not characterized by certain hypersurface, holographic, or duality properties. For such solutions, the Bekenstein-Hawking paradigm [113,114] is not applicable and we have to elaborate on theories of nonholonomic and Finsler geometric flows. Here, we cite our and co-authors’ works beginning 2006, [53,115,116,117,118,119]. Recent results and methods on nonholonomic or nonmetric geometric and quantum information flows and FLH, and other types of MGTs can be found in [13,98,107]. Such works are also related to a series of papers on Finsler-like diffusion, locally anisotropic kinetic processes, locally anisotropic thermodynamics, etc. [17,120,121,122,123,124].- Certain different Renaissance directions were developed by other authors (we reviewed and discussed the most important contributions till 2018 in Appendix B of the preprint variant of [17]). Here we note that those results and methods do not allow for the construction in general forms of certain off-diagonal solutions, depending on the type of Finsler generating functions and prescribed connections. They are different from our approach to FLH and can be incomplete for applying the AFCDM. The fiber (tangent or vector ....) bundle formalism was not applied in elaborating such theories, which put many questions on mathematical rigorous formulation. In many cases, those models and a few found diagonalizable solutions of Finsler-like gravitational equations are with a trivial N-connection structure. Typically, they consist of arbitrary lifts and deformations on y-variables that are not derived as certain exact or parametric solutions involving Sasaki lifts and an axiomatic formulation and self-consistent physical formulation.
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Nowadays and Future (2012 - ...) After many observational evidences on accelerating cosmology and validating papers of various MGTs and DM and DE physics [5,6,7,8,9,10,11,12], Phys. Rev. D and other influential physical journals began to publish papers on Finsler geometry and applications in modern physics, cosmology and astrophysics [82,125,126,127,128,129,130,131,132,133,134]. New international and multi-disciplinary teams and research groups (originating from Greece, Germany, China, Romania, R. Moldova, Spain, Italy, India, Iran, etc.) have been organized during the last 15 years. We discussed the main developments (till 2018) in Appendix B of the preprint part of [17]. The discovery of late-time cosmic acceleration [5,6] resulted in extensive research on modified gravity theories (MGTs) [7,8,9,10,11] and dark energy (DE) and dark matter (DM) physics [12] Here we analyze in brief some recent results on FLH MGTs and applications, which are relevant to the purposes of this work:- Undetermined concepts of pseudo-Finsler spacetime, causality, and problems with nonmetric Finsler gravitational equations. Such geometric models and possible applications were elaborated in a series of works [125,126,127,133,134,135,136]. This group of authors try to impose a Finsler spacetime standard (publishing in Phys. Rev. D and other influential journals). Former important and more general results and methods (from the periods when Finsler gravity was considered "unphysical") typically are not cited and not discussed, as we described above in 5], and reviewed in [17]). The main idea of the mentioned team of authors was to extend the concept of pseudo-Riemannian geometry in certain causal, with a well-defined theory of observations, and for a concept of pseudo-Finsler spacetime, by postulating a version of locally anisotropic gravitational equations. For instance, such a pseudo-Finsler spacetime can be defined by some data where V is a pseudo-Riemannian manifold and is a Finsler generating function. Additional assumptions are necessary to define certain causality and postulates and to derive in geometric or variational forms some Finsler-like gravitational equations, for instance, of type [125,126], etc. This is not enough for formulating generalizations of Einstein gravity if we do not prescribe some classes of nonlinear and distinguished Finsler d-connections on (co) tangent Lorentz bundles. Well-motivated physical arguments (general theoretic/ phenomenological or observational/experimental one) are necessary for prescribing an F (why it should be homogeneous?) and certain types of N- and d-connections, or to motivate certain very special relativity models. In [127], a procedure on how to make extensions of the Lorentzian spacetime geometry "from Finsler to Cartan can vice versa" is analyzed. Then, in [135], a Birkhoff theorem was proved for Berwald-Finsler spacetimes. Nevertheless, Berwald, Chern or other type of nonmetric d-connections (reviewed in [136]) result in many difficulties in definition of Finsler like versions of the Einstein-Dirac equations, as we explained above in paragraph 6.2] (see also criticisms in [17,19,36]). In principle, a cure can be provided by formulating Finsler methods involving the canonical d-connection and distortions of linear connection structures as in [37] (necessary definitions and formulas will be provided in the next section).- The variant of Finsler geometric extension of GR [125,126] (and related models with metrizability conditions) does not allow construction of exact or parametric solutions [136] in certain general forms with nontrivial N-connection structure and using Sasaki lifts [45]. Such variants of Finsler-like gravitational equations consist just of an example reflecting priorities of a group of authors when other more general approaches were elaborated (as we motivated in [17,19]). Any axiomatic approach for the Finsler gravity theories [125,126] depends on the type of geometric structures, conditions of causality, (homogeneity conditions on the types of N- and d-connections) and other assumptions on deriving Finsler modified gravitational equations. Mentioned authors do not cite and do not apply the AFCDM described above in 6.1]. Our main idea was to elaborate on FLH theories in general forms on (co) tangent Lorentz bundles, which allow a straightforward generalization of the axiomatic approach to GR [17]. Then we can apply the AFCDM for respective classes of distortions of connections, Sasaki-type d-metrics with respective gravitational polarizations, and effective sources, and construct very general classes of off-diagonal solutions. After certain classes of physically important solutions have been constructed in some general forms, we can analyze if additional homogeneity conditions on (effective) Finsler-Lagrange, or Cartan-Hamilton, generating functions and generating sources can be imposed. This way, we can extract, for instance, Fisler-Cartan, Finsler-Berwald, or other types of configurations. Certain conditions for generating off-diagonal solutions for a base Lorentz spacetime manifold (as in GR but, for instance, with anisotropic polarizations of physical constants) can also be formulated. We shall provide important examples in Section 5. Such results can’t be obtained if we follow only the geometric approach and methods elaborated in [125,126,127,133,134,135,136] (only certain particular examples of vacuum solutions were found by these authors). More than that, it is not clear how to define self-consistently and solve the respective Finsler deformed EYMHD equations.- Barthel-Randers/-Kropina-type Finsler geometries and cosmological implications. A series of such applications in modern cosmology and DM and DE physics was elaborated recently in [137,138,139]. N-adapted Sasaki-type metrics are used for defining d-metrics on total tangent bundles. In [137], the gravitational field equations are derived using Akbar-Zadeh geometric lifts (Ricci type) tensors [140,141]. Further developments [138,139] involve so-called metrics, Kropina metrics, the Barthel connection etc. Such models can be subjected to cosmological tests and may explain certain DE properties. Nevertheless, the simplifications for respective classes of d-metrics and d-connections (and respective osculator constructions) do not have theoretical motivations in the conditions when the AFCDM allows us to construct more general classes of off-diagonal locally anisotropic cosmological solutions. Even if we begin with a variant of Barthel-Randers/ - Kropina-type configuration, the geometric evolution and off-diagonal dynamics transform such Finsler geometric data into another type ones. The issues on constructing Barthel-Randers/-Kropina-type deformations of EYMHD systems and constructing respective classes of solutions have not been analyzed in [137,138,139] and further developments. We analyze how to solve such problems in the next sections.- Fibered structures in (pseudo) Finsler geometry, causality, and variational formalism. A series of such works was published by research groups in mathematics and mathematical physics [142,143,144] (see also references therein). A class of static vacuum solutions of the Einstein equations were extended for a model of Finsler-Berwald spacetimes with vanishing Ricci scalar. For such constructions, a concept of Finsler spacetime was considered for a smooth finite dimensional manifold endowed with a Lorentz-Finsler metric. More general models with the Chern connection and Akbar-Zadeh were also considered, and the conditions for embedding such solutions to solve Rutz’s equations [61] were stated. Then, a metric-affine version of the Finslerian Einstein equations was derived using the Palatini formalism [143]. Such equations depend on the type of N-connection and d-connection structures. Nevertheless, it is not clear how to solve such locally anisotropic gravitational and matter field equations in certain general forms and to find physically important solutions. Physically viable models of anisotropic gravity with a respective action integral for a Finsler gravity theory can be obtained by pulling back and Einstein-Cartan-like Lagrangian from the tangent bundle to the base manifold [144]. To find solutions (vacuum ones and for nontrivial matter field sources) in such an approach is a difficult technical task.- Physically important black hole (BH), wormhole (WH), and cosmological solutions. Such new numeric and graphic methods were elaborated in [145,146,147]. Typically, the Finsler-Runders geometry with the Barthel connection is used for finding solutions of the Finsler-like gravitational equations from [129] and/or using the Akbar-Zadeh definition of Ricci tensors for Finsler spaces [140,141]. Such solutions are not derived in a unique and complete form on tangent Lorentz bundles and consist of arbitrary lifts because certain variants of Sasaki d-metrics are not defined [17,75,86,101,148,149]. In principle, to reconstruct such BH, WH, and locally anisotropic configurations is possible in general and self-consistent forms as in [13,107,150,151,152] (we explain this in Section 5). In our works, we applied the AFCDM in its nonassociative/noncommutative, supersymmetric and other type generalizations. For FLH theories (in general form, not only for certain Finsler-Randers generating functions and Berwald or Barthel connections), we consider different types of nonholonomic structures. This allows us to construct exact and parametric off-diagonal solutions for FLH theories defined on (co) tangent Lorentz bundles.- Finsler-Randers-Sasaki gravity and cosmology. A series of recent works [153,154,155,156,157], see also [128], is devoted to constructing of exact and parametric solutions (and applications in modern cosmology and astrophysics). This direction of research is close to our research programs on FLH MGTs and applications. Our collaboration with Prof. P. Stavrinos and other co-authors in 2000 [19,64] is reviewed [17]. The most common points are those that we elaborate our geometric and physical models on (co) tangent Lorentz bundles, using Sasaki-type d-metrics, metric-compatible Cartan or canonical d-connections, etc. The main difference is that in our works we construct off-diagonal solutions encoding FLH deformations in most general forms (not for any special classes of Finsler generating functions, like Randers types encoding a covector field as a linear y-contributions). Even if we begin with certain particular Finsler configurations (Randers or another type) the geometric evolutions/ dynamics of corresponding Sasaki type d-metrics and distortion of N- and d-connections transform substantially the target d-metrics. To prove this is possible if we apply the AFCDM as in [17,25,26,158] for FLH geometric flow and MGTs. Here we also emphasize that using respective nonholonomic frame transforms, and distortions of connections, we can reproduce as particular cases any class of solutions in Finsler-like theories 7.2-7.5].
1.2. The Hypotheses, Objectives and Structure of the Review
- H1.
- The axiomatic formulation of the Einstein gravity theory on Lorentz manifolds can be extended for Finsler-like gravity theories in physically motivated, self-consistent, and mathematically rigorous forms on (co) tangent Lorentz bundles. In general forms, the nonholonomic geometric formulation of such FLH MGTs is similar to metric-affine geometry, when the fundamental geometric objects and physically important systems of nonlinear PDEs can be adapted to a prescribed N-connection structure. The nonmetric generalizations are performed by using distortions of Finsler-like connections used in metric-compatible theories (such constructions may involve, or not, nontrivial torsion structures). Explicit examples of FLH MGTs can be derived by postulating respective classes of Lagrangian or Hamiltonians, or certain almost symplectic structures, and by prescribing corresponding classes of FLH generating functions. Such generating functions and effective sources can be with homogeneity conditions, or with other types of prescribed symmetries, N-connections, and d-connections. General frame/coordinate transforms and distortions of connections on (co) tangent Lorentz bundles (in particular, on base spacetime manifolds), and respective classes of off-diagonal solutions of fundamental systems of nonlinear PDEs, mix the types of FLH theories and may transform them into general nonholonomic MAG theories.
- H2.
- Considering N-adapted geometric flows on a (temperature-like) -parameter involving respective distortions of connections and Sasaky-type d-metrics, we can generalize the theory of Ricci flows for respective nonolonomic geometric flows of FHL theories. In relativistic forms, such FLH-flows are modelled on (co) tangent Lorentz bundles. Considering N-adapted (3+1)+(3+1) splitting, the G. Perelman’s statistical and geometric thermodynamics can be generalized for FLH and various types of MGTs. For such modifications, explicit formulations and proofs of certain generalized Poincaré-Thurston conjectures are not possible because the topological and geometric analysis constructions depend on the types of N- and d-connections and respective distortions. Nevertheless, formal generalizations and respective general decoupling and off-diagonal integration properties of the modified R. Hamilton and D. Friedan geometric flow equations can be proven for general classes of distortion relations, generating functions and sources. This allows us to compute the modified G. Perelman thermodynamic variables for respective classes of FLH theories, and important classes of solutions, and speculate on the physical importance and possible application of such theories or classes of solutions. The dynamical FLH gravitational and (effective) matter field equations stated by H1 can be considered as specific examples of FLH Ricci solutions, which are derived as self-similar nonholonomic geometric flow configurations for a fixed
- H3.
- The fundamental geometric and physically important systems of nonlinear PDEs considered for H1 and H2 (FLH modified geometric flow or gravitational and matter field equations) can be decoupled and integrated in general off-diagonal forms using the AFCDM. Such geometric and analytic methods allow us to generate physically important exact and parametric solutions using respective dyadic variables with conventional nonholonomic (2+2)+(2+2) decompositions. For respective subclasses of generating and integration functions, we can define FLH modifications/ versions of BH, WH and BT solutions. In dual forms, with respective nonlinear symmetries, we can elaborate on locally anisotropic cosmological models with implications in modern DE and DM physics. Typically, the Bekenstein-Hawking paradigm does not apply to characterizing physical properties of such FLH theories and respective classes of solutions. Changing the statistical thermodynamic paradigm to that for G. Perelman’s thermodynamics of Ricci flows, we can investigate in a more general form the physical properties of such nonlinear systems under nonholonomic geometric evolution and/or with dynamical off-diagonal interactions.
- H4.
- Certain Finsler-like MGTs are used to study new (non) metric and nonlinear physical effects and observational features of accelerating cosmology, DE and DM theories. This involves both conceptual and technical problems if we consider FLH non-standard models of particle physics with nonmetricity fields. In such cases, to define in a unique form Finsler variants of the Dirac operator and respective FLH modifications of the Einstein-Dirac, ED, equations are not possible. For the canonical d-connection, which is metric compatible and can be related via frame transforms to the Cartan-Finsler d-connection, the constructions for Clifford structures are similar to those in GR, but result in ambiguities, for instance, for the Chern-Finsler d-connection (because of nonmetricity). In our approach, we can define FLH-modifications of certain well-defined EYMHD systems possessing physically motivated solutions in nonholonomic dyadic variables and canonically adapted (non) linear connection structures. For such configurations, the AFCDM allows us to decouple and integrate in a certain general off-diagonal form and generate both metric-compatible and nonmetric solutions. Various classes of solutions in GR and MGTs defined on Lorentz spacetime manifolds can be extracted for certain particular parameterizations of general generation and integration data. Using the formalism of N-adapted distortion of linear connections nonholonomic dyadic variables, and canonically adapted (non) linear connection structures, the AFCDM allows decoupling and integrating in a certain general off-diagonal form the nonmetric FLH geometric evolution flow equations and related dynamical (non) metric EYMHD equations. All new classes of off-diagonal solutions for nonmetric FLH geometric flow equations, with nonholonomic Ricci soliton configurations for EYMHD systems, etc., are characterized by generalized G. Perelman thermodynamic variables.
- H5.
- FLH geometric flow and MGTs can be quantized by using nonholonomic generalized methods of deformation quantization, generalized Batalin-Fradkin-Vilkovisky quantization methods, etc. Generalized QG theories with local anisotropy and modified dispersion relations, for FLH models, can be elaborated in certain compatible forms with the (super) string/ M-theories. In general, they involve nonassociative and noncommutative R-flux modifications and nontrivial Lie-algebroid structures and gerbes. Such constructions result in new types of nonmetric FLH geometric and quantum flow information theories, and locally anisotropic kinetic, diffusion and geometric thermodynamic models.
2. Nonholonomic Metric or Nonmetric Geometry and FLH-Modified Einstein Gravity
- In MGTs, we can define N-connection structures determined by semi-spray equations, i.e. nonlinear geodesic equations. Such equations are equivalent to the Euler-Lagrange and/or Hamilton equations [32,46,47]. This results into alternative formulations of geometric mechanics, which may involve supersymmetric/ nonassociative and other types nonholonomic variables [19,62].
- Non-geometric star product R-flux deformations in string theory [15,162,163] can be geometrized in nonassociative and nonholonomic forms on 8-d phase spaces involving complex or real momentum variables [13,18,26]. Star product R-flux deformations can be also characterized by MDRs encoding nonassociative and noncommutative data. We also can elaborate on (super) string and supergravity theories when extra dimension coordinates are velocity/momentum type [17,19,71,72,73]. To prove general decoupling and integration properties of physically important systems of nonlinear PDEs in such theories, we have to consider nonholonomic dyadic decompositions and certain classes of generalized metrics and linear connections adapted to N-connection structures. Such geometric methods were elaborated in Finsler geometry.
- New classes of generic off-diagonal solutions with effective sources in MGTs on (nonassociative, noncommutative, supersymetric, etc.) phase spaces, or nonholonomic Lorentz manifolds, are characterized by G. Perelman statistical and geometric thermodynamic models [108] which are generalized for nonassociative Finsler-Lagrange-Hamilton geometric flow and nonholonomic Ricci soliton theories [53,115,116,117,118,119]. We cite [13,98,107] for recent results and methods (which were originally formulated in Finsler geometry) on nonholonomic or nonmetric geometric and quantum information flows and FLH, and other types of MGTs.
- We elaborated the AFCDM as a geometric and analytic method for constructing generic off-diagonal solutions in GR and various types of MGTs by using nonholonomic dyadic frames and certain canonical d-connections defined as in Finsler geometry, see recent reviews of results in [17,18,25,26,152]. Conventional nonholonomic 2+2 and (2+2)+(2+2) etc. splitting (respectively, for 4-d GR and MGTs and for 8-d FLH gravity theories) were used. New classes of Finsler-like solutions were constructed for elaborating various models of nonlinear classical and quantum theories, locally anisotropic thermodynamics, diffusion and kinetics, and effective DE and DM physics.
2.1. E. Cartan’s Approach, Canonical d-Connections, and Relativistic FLH Geometry
2.1.1. Finsler-Cartan Geometry
2.1.2. N-Connection Structures for FL and FH Spaces
2.1.3. Canonical d-Metrics in Relativistic FL and FH Geometry
2.1.4. General Covariance, Modified Dispersion Relations and Nonholonomic FLH Variables
2.1.5. Almost Symplectic Variables in FLH Geometry
2.2. General and Canonical FLH d-Connections and Distortion d-Tensors
2.2.1. Affine Connections, d- and s-Connections in FLH Geometry
2.2.2. Physically Important and Canonical and Dyadic FLH d-Connections
- [a]
- The LC-connections and can be defined in standard forms using corresponding d-metrics (13) and (14), or (23) and (24), or (15) and (16), or their off-diagonal representations for coordinate bases on phase spaces. Such linear connections can be used for elaborating FLH models by analogy to higher dimension extensions of the Einstein gravity, when extra-dimension coordinates are velocity or momentum type. We can construct diagonal configurations, for instance, certain BH solutions as in higher dimension gravity, in string gravity theories, etc., see discussions in [17,18,19]. To construct generic off-diagonal solutions using only ∇ or is a very difficult task because we are not able to prove any general decoupling properties. We can encode in such LC-configurations certain FLH data, but in general such theories are not Finsler-like because the LC-connections are not adapted to certain N-connection structures. Here we note that any metric-affine phase space geometry defined by some data involves bi-connection, and distortion configurations, If we introduce a N-connection structure on , we can perform N-adapted geometric constructions with as on nonholonomic manifolds and (co) tangent bundles. Corresponding bi-connection, and distortion N-adapted configurations, can be also defined. To prescribe/ or define an N-connection structure is crucial for constructing FLH theories even, in general, a d-connection can be an arbitrary one. A distortion d-tensor can be determined from certain fundamental geometric of modified gravitational field equations for a postulated FLH or other type MGT. Here we note that N- and d-connections can also be introduced in GR and "non-Finsler" gravity theories if we prescribe a N-connection as nonholonomic distribution on a V and, respectively, . For non-FLH theories, the N-connection structure is not obligatory of type (8) but can be a general one (17). Nevertheless, nonholonomic dyadic splitting and distortion of connection formalism are important for all MAG theories because they allow applications of the AFCDM for constructing off-diagonal solutions. For dual phase spaces, the above formulas are determined by a distortion relation of type
- [b]
- The almost symplectic d-connections and (respectively on and ) are very important because they are also equivalent to the Cartan d-connection in Finsler geometry, see details and index formulas in [17,19,29,30,127]. In abstract geometric form, such nonholonomic geometries are determined, respectively, by and The corresponding phase space gravitational field equations possess very special integration properties [22,75,101] but not general ones. The main priority of such d-connections defined for Finsler-like variables is that we can perform DQ of FLH MGTs and GR [18,51,52,53,54,105]. Nevertheless, to prove certain general off-diagonal decoupling properties of corresponding dynamical or geometric flow equations is not possible if we work only with the LC-connection.
- [c]
- The almost symplectic d-connections and (respectively on and ) are very important because they are also equivalent to the Cartan d-connection in Finsler geometry, see details and index formulas in [17,19,29,30,127]. In abstract geometric form, such nonholonomic geometries are determined, respectively, by and The corresponding phase space gravitational field equations possess very special integration properties [22,75,101] but not general ones. The main priority of such d-connections defined for Finsler-like variables is that we can perform DQ of FLH MGTs and GR [51,52,53,54,105]. Nevertheless, to prove certain general off-diagonal decoupling properties of corresponding dynamical or geometric flow equations is not possible if we work only with the LC-connection.
- [d]
- The main goal of this work is to study nonholonomic metric-affine FLH theories adapted to N-adapted structures determined by respective geometric data and and show how the AFCDM can be applied in such a case. We can consider theories when, for instance, (see definition in (36)) is a d-connection with nontrivial nonmetricity but with zero torsion. This provides a tangent Lorentz bundle generalization of MAG theories [14,19], in particular, of gravity [16,37]. The AFCDM can be generalized for such 4-d and 8-d theories (or other dimensions), which allows us to construct generic off-diagonal solutions for nonmetric FLH theories (see Section 4 and Section 5). Finsler-like theories with nonmetricity were criticised in [17,19,36] because of the problems with definitions of general nonmetric spinors and the Dirac equation. Nevertheless, we can elaborate on nonmetric FLH modifications of ED systems using the same nonholonomic methods as in [37] (using velocity/ momentum variables, we shall study this problem in our further partner works).
- [e]
- We can consider metric-affine structures or on respective (co) tangent Lorentz bundles and postulate certain types of generalized gravitational field equations with nontrivial torsion and nonmetricity fields. Such phase space MGTs can’t be integrated in general forms if certain special diagonal ansatz are not considered. It is not clear how to define a self-consistent metric-affine geometric flow models and respective nonmetric generalizations of EYMHD systems etc. Introducing formal s-connection structures (17), with respective distortions and s-adapted frames, we can generate solutions for physically important systems of nonlinear PDEs. We can speculate when such MGTs can be related to certain FLH configurations if certain effective backgrounds are determined by velocity/ momentum - like variables. This can be performed for respective nonholonomic dyadic splitting when, for instance, see also distortions (35).
2.2.3. Distorting Curvature, Torsion, Nonmetricity and Ricci s-Tensors
2.3. Metric and Nonmetric FLH-Deformed Einstein Equations
2.3.1. Canonical Nonholonomic Metric Affine Structures in FLH Gravity
2.3.2. FL Deformed Nonmetric f(Q) Gravity and Modified Einstein Equations
2.3.3. FH Deformed Nonmetric f(Q) Gravity and Modified Einstein Equations
2.3.4. Canonical Integrable Nonmetric FLH Deformed Gravitational Phase Space Equations
2.3.5. Modelling, Distorting, or Extracting Gravitational Field Equations in GR and FLH MGTs
3. Metric and Nonmetric Geometric FLH-Flows and Ricci Solitons
3.1. Metric Compatible FL and FH Deformed Geometric Flows
3.1.1. F- and W-Functionals for FL and FH Flows
3.1.2. Thermodynamic Models for FL and FH Flows
3.2. Nonmetric Geometric Flow Equations in Canonical Dyadic Variables
3.2.1. Q-Distorted R. Hamilton and D. Friedan Equations
3.2.2. -Running Nonmetric Einstein Equations for Nonmetric Geometric Flows
3.3. Statistical Geometric Thermodynamics for Geometric Flows
3.3.1. Nonholonomic F-/ W-Functionals for Q-Deformed Geometric Flows and Gravity
3.3.2. Canonical Thermodynamic Variables for Theories
3.4. Different Thermodynamic Formulations of (Non) Metric FLH Theories
4. Decoupling and Integration of (Non) Metric FLH-Flows and Modified Einstein Equations
4.1. Off-Diagonal and s-Adapted Ansatz for Metrics and Canonical d-Connections
4.2. Decoupling of Nonmetric FLH Geometric Flow and Modified Einstein Equations
4.3. Integration of Nonmetric FLH Geometric Flow Equations
4.3.1. Different Forms of Quasi-Stationary Solutions and Their Nonlinear Symmetries
- Above classes of such solutions are with nontrivial geometric flows of nonholonomic torsion, which is not zero for hat variables. We can define certain classes of nonholonomic frame transforms and distortions of the canonical s-variables when the FL geometric evolution is described by families of LC-connections
- We can compute necessary thermodynamic variables (92) associated with canonical quasi-stationary solutions, or their time dual ones defined as locally anisotropic cosmological solutions with additional cosmological flow. In the next section, we shall provide such examples for nonassociative BH and WH configurations.
- The solutions for FL Ricci soliton equations (85) consist self-similar configurations of (81) with We can construct such quasi-stationary solutions directly or after a class of generic off-diagonal solutions was constructed for FL geometric evolution flows. Such nonholonomic Ricci soliton configurations can be generated equivalently by solutions constructed using the AFCDM as it is outlined in Appendix B.
- Finally, we note that -families of nonholonomic FLH quasi-stationary solutions can be generated using Table A5, Table A6, Table A10 and Table A11 (see respective ansatz (A31), (A32), (A34) and (A35)) when the s- and N-coefficients are considered with additional -dependence and the generating sources (111) are correspondingly redefined for FH distortions and .
Nonlinear Symmetries of Quasi-Stationary Configurations
4.3.1.2. Quasi-Stationary Solutions with Effective Cosmological Constants
4.3.1.3. Solutions When Some D-metric Coefficients are Used as Generating Functions
4.3.1.4. Quasi-Stationary Gravitational Polarizations of Prime S-Metrics
4.3.2. Dualities of Space and Time, and Space Momenta and Energy, for Off-Diagonal Solutions
4.3.3. Constraints on Generating Functions and Sources for Extracting LC Configurations
4.4. Mutual Transforms of FLH Geometric Flow and MGTs and Their Classes of Solutions
- Certain FLH models may transform equivalently, or partially, in other types of FLH theories (which can be metric compatible or not).
- A class of off-diagonal exact/parametric solutions can be transformed in another class of off-diagonal solutions of the same FLH MGT model. In particular, we can chose a prime s-metric which is not a solution of some FLH-modified Einstein equation and transform it in a target s-metric which is a solution of FLH geometric flow, or nonholonomic Ricci soliton, equations.
4.4.1. Thermodynamic Variables for FLH Geometric Flows of Nonmetric Quasi-Stationary Configurations
4.4.2. Nonholonomic Distortions and Equivalence of FLH Theories
4.4.3. Equivalent Modelling and Different Classes of FLH Solutions
5. Examples of FLH-Modified Off-Diagonal Solutions
5.1. FLH Geometric Flows of New Kerr de Sitter BHs to (Double) Spheroidal Configurations
5.1.1. Prime New KdS Metrics and Gravitational Polarizations
5.1.2. Nonmetric FLH Geometric Flow Off-Diagonal Deformations of KdS Metrics
5.1.3. Off-Diagonal Solutions with Small Parametric Deformations of KdS d-Metrics
5.1.4. Double BE Solutions in Nonmetric FLH Geometric Flow and MGTs
5.1.5. Perelman Thermodynamic Variables for General Off-Diagonal Deformed KdS BHs
- a]
- b]
- (142), when the gravitational -polarizations are defined by -running s-metrics involving a small parameter The corresponding volume functional can be computed in -parametric form.
- c]
- when the prime data (144) are chosen to define double BE configurations. We have possibilities to define and compute a volume functional (131) on the 8-d phase space, and a similar projection for geometric flows on base Lorentz manifold, where the h-projection is defined by A similar volume form can be computed for the typical fiber with which may result in a "nonstandard" thermodynamic model for velocity type variables.
5.1.6. Discussion of Alternative BH Solutions in Finsler-like MGTs
5.2. Off-Diagonal FLH Geometric Flow Deformed WHs
5.2.1. FL Quasi-Stationary Gravitational Polarizations of WHs in GR and Lifts to Phase Spaces
5.2.2. Small Parametric FLH Quasi-Stationary Deformations of WH d-Metrics
5.2.3. G. Perelman Thermodynamic Variables for FLH Off-Diagonal Deformed WHs
5.3. Nonholonomic Toroid Configurations and Black Torus, BT
Relativistic Ricci Flow Thermodynamic variables for FLH BTs
5.4. Off-Diagonal 4-d Cosmological Solitonic and Spheroid Cosmological Solutions Involving 2-d Vertices
5.4.1. Off-Diagonal Transforms of Cosmological Models with Spheroidal Symmetry and Voids
5.4.2. Off-Diagonal Cosmological Solitonic FLH Evolution Encoding 2-d Vertices
5.5. Double Off-Diagonal (4+4)-d Cosmological Solitonic and Spheroid Cosmological Involving 2-d Vertices
Geometric Flow Thermodynamics for Off-Diagonal FLH Cosmological Solutions
6. Conclusions and Perspectives
Acknowledgments
Appendix A. Proofs of Decoupling and Integrating Nonmetric FLH-Geometric Flow Equations
Appendix A.1. Canonical Ricci s-Tensors for Quasi-Stationary Configurations
Appendix A.1.1. Conventions on Quasi-Stationary Ansatz and their Dualization to Locally Anisotropic Cosmological Configurations
Appendix A.1.2. Computing the Coefficients of the Canonical s-Connection
Appendix A.1.3. Computing the Coefficients of the Canonical Ricci and Einstein s-Tensors
Appendix A.2. Off-Diagonal Integration of Decoupled FLH Geometric Flow Modified Einstein Equations
Appendix A.3. Off-Diagonal Quasi-Stationary Solutions with Small Parameters
Appendix B. Tables A1–A13 for Generating Off-Diagonal Solutions in FLH Theories
Appendix B.1. Nonmetric 4-d Off-Diagonal Quasi-Stationary and Cosmological Solutions, Table A1–Table A3
Appendix B.1.1. Ansatz for 4-d Metrics and d-Metrics and Systems of Nonlinear ODEs and PDEs
| diagonal ansatz: PDEs → ODEs | AFCDM: PDEs with decoupling; generating functions | |
|---|---|---|
| radial coordinates | nonholonomic 2+2 splitting, | |
| LC-connection | [connections] | |
| [coord.frames] | ||
| [N-adapt. fr.] | ||
| Ricci tensors | ||
| generating sources |
||
| trivial equations for -torsion | LC-conditions |
Appendix B.1.2. Decoupling and Integration of (Modified) Einstein eqs & Quasi-Stationary Configurations
| Effective matter sources | ||
| Nonlinear PDEs (99)-(102) | for | |
| Off-diag. solutions, | ||
| LC-configurations (128) | ||
| N-connections, zero torsion | ||
| Prime metric defines a BH | ||
| Example of a prime metric | ||
| Solutions for polarization funct. | ||
| Polariz. funct. with zero torsion |
Appendix B.1.3. Decoupling and Integration of 4-d Gravitational PDEs Generating Cosmological s-Metrics
| Effective matter sources | ||
| Nonlinear PDEs | for | |
| Off-diag. solutions, | ||
| LC-configurations | ||
| N-connections, zero torsion | ||
| Solutions for polariz. funct. | ||
| Polariz. funct. with zero torsion |
Appendix B.2. Off-Diagonal Velocity Depending Quasi-Stationary or Cosmological FL Solutions
Appendix B.2.1. Diagonal and Off-Diagonal Ansatz for Velocity Phase Spaces and FL Geometric Flows
| diagonal ansatz: PDEs → ODEs | AFCDM: PDEs with decoupling; | |
|---|---|---|
| coordinates |
||
| LC-connection | N-connection; canonical d-connection |
|
| [coord.frames] | ||
| [N-adapt. fr.] |
⋮ |
|
| Ricci tensors | ||
| generating sources |
||
| trivial eqs for -torsion | LC-conditions |
Appendix B.2.2. Quasi-Stationary Solutions for Nonmetric FL Geometric Flows with Fixed Light Velocity
| Effective matter sources | ||
| Nonlinear PDEs (99)-(102) | ||
| Off-diag. solutions, |
Appendix B.2.3. Quasi-Stationary Nonmetric Solutions with Variable Light Velocity
| Effective matter sources | ||
| Nonlinear PDEs (99)-(102) | ||
| Off-diag. solutions, |
Appendix B.2.4. Nonmetric Locally Anisotropic Cosmological Solutions with Phase Space Velocities
| Effective matter sources | ||
| Nonlinear PDEs (99)-(102) | ||
| Off-diag. solutions, |
Appendix B.2.5. Nonmetric Cosmological Solutions with Phase Space Rainbow Symmetries
| Effective matter sources | ||
| Nonlinear PDEs (99)-(102) | ||
| Off-diag. solutions, |
Appendix B.3. Momentum Depending Quasi-Stationary and Cosmological Solutions
Appendix B.3.1. Off-Diagonal Ansatz for Nonmetric Geometric Flows on Momentum Phase Spaces
| diagonal ansatz: PDEs → ODEs | AFCDM: PDEs with decoupling; | |
|---|---|---|
| coordinates |
||
| LC-connection | N-connection; canonical d-connection |
|
| [coord.frames] | ||
| [N-adapt. fr.] |
⋮ |
|
| Ricci tensors | ||
| generating sources |
||
| trivial eqs for -torsion | LC-conditions |
Appendix B.3.2. Quasi-Stationary FH Nonmetric Solutions with Fixed Energy Parameter
| Effective matter sources | ||
| Nonlinear PDEs (99)-(102) | ||
| Off-diag. solutions, |
Appendix B.3.3. Quasi-Stationary and Rainbow Phase Space Solutions
| Effective matter sources | ||
| Nonlinear PDEs (99)-(102) | ||
| Off-diag. solutions, |
Appendix B.3.4. Locally Anisotropic Nonmetric Cosmological Solutions with Fixed Energy Parameter
| Effective matter sources | ||
| Nonlinear PDEs (99)-(102) | ||
| Off-diag. solutions, |
Appendix B.3.5. Locally Anisotropic Nonmetric Cosmological Solutions with Variable Energy Parameter
| Effective matter sources | ||
| Nonlinear PDEs (99)-(102) | ||
| Off-diag. solutions, |
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| 1 | In our approach V is a four dimensional (4-d) Lorentz manifold as in GR; and and are respective tangent and cotangent Lorentz bundles with respective local coordinates and Indices run values where is the time like coordinate (typically we use systems of unities when the speed of light and consider necessary auxiliary constants to work with dimensionless geometric and physical objects); and, for velocity and momentum type coordinates, where are considered as cumulative (total space) indices. In this work, we shall give priority to the abstract geometric formulation of GR and MGTs as in [2,13,17] (with various abstract left-up and low labels), but certain coefficient formulas will be used for constructing exact and parametric solutions. Boldface symbols are used for denoting N-adapted geometric objects, and respective geometric constructions and "" emphasizes that the formulas involve momentum-like variables on Tilde on geometric objects is used to emphasize that we work in the framework of the Finsler-Cartan geometry. All necessary definitions and notations will be provided and explained in the next sections and appendices to this paper. In the introduction section, we follow standard and abstract notations on geometric objects in FLH theories elaborated in [17,19]. |
| 2 | Here we note that a nonholonomic manifold is a standard manifold M of necessary smooth class endowed with a nonholonomic (equivalently, anholonomic, or non-integrable) distribution. A nonlinear connection, N-connection structure , used in Finsler geometry models defined on tangent bundle can be defined equivalently as a Whitney sum: where h and v are used, respectively, for conventional horizontal and vertical splitting. All necessary definitions and details will be provided in the next section and Appendix. |
| 3 | Necessary formulas (3) and explanations are provided in next section. In this subsection, we use only the definitions and notations which are important for stating the hypotheses and objectives of this work. |
| 4 | |
| 5 | |
| 6 | We note that, the geometric constructions can be performed similarly for higher dimensions (with extra dimension pseudo-Riemannian coordinates as in Kaluza-Klein or string gravity theories) and other types of MGTs. We can elaborate also on or gravity [7,8,9,10,11,14,16] effectively modelled on 4-d Lorentz manifolds. In this work, we assume that the GR can be modeled only on a 4-d base spacetime manifold V when the fundamental geometric structures are subjected to Finsler-like nonholonomic generalizations for MGTs formulated on certain total (co) tangent Lorentz bundles. |
| 7 | We follow such additional conventions: A v-metric and a c-metric are labeled by a tilde "~" to emphasize that such conventional v–metrics and c-metrics are defined canonically by respective Lagrange and Hamilton generating functions. General frame/ coordinate transforms on and/or allow us to express any "tilde" Hessian in a general form, respectively as a vertical metric (v-metric), and/or co-vertical metric (cv-metric), We can also works with inverse frame/ coordinate transforms by prescribing any v-metric (cv-metric). In general, a is different from the inverse of i.e. from . In explicit form, certain Lagrange and/or Hamilton models on corresponding and/or can be always constructed by prescribing certain generating functions and/or We shall omit tildes on geometrical/ physical objects if certain formulas hold true in general forms and not only for some canonical structures and if that will not result in ambiguities. |
| 8 | They include nonholonomic torsion components but in a form which is different from (for instance) the Riemann-Cartan theory or string gravity with torsion. In those gravity models, there are considered algebraic equations for motivating torsion fields as generated by certain spin-like fluids with nontrivial sources or certain other completely anti-symmetric torsion fields. |
| 9 | In this work, we follow a different system of notations and chose an opposite sign before
|
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