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We establish the mathematical fundamentals for a unified description of curvature, torsion, and non-metricity 2-forms in the way extending the so-called Möbius representation of the affine group, which is the method to convert the semi-direct product into the ordinary matrix product, to revive the fertility of gauge theories of gravity. First of all, we illustrate the basic concepts for constructing the metric-affine geometry. Then the curvature and torsion 2-forms are described in a unified manner by using the Cartan connection of the Möbius representation of the affine group. In this unified-description, the curvature and torsion are derived by Cartan’s structure equation with respect to a common connection 1-form. After that, extending the Möbius representation, the dilation and shear 2-forms, or equivalently, the non-metricity 2-form, are introduced in the same unified manner. Based on the unified-description established in this paper, introducing a new group parametrization and applying the Inönü–Wigner group contraction to the full theory, the relationships among symmetries, geometric quantities, and geometries are investigated with respect to the three gauge groups: the metric-affine group and its extension, and an extension of the (anti)-de Sitter group in which the non-metricity exists. Finally, possible applications to theories of gravity are briefly discussed. [ABSTRACT FROM AUTHOR]

Realism about general relativity (GR) seems to imply realism about spacetime curvature. The existence of the teleparallel equivalent of general relativity (TEGR) calls this into question, for (a) TEGR is set in a torsionful but flat spacetime, and (b) TEGR is empirically equivalent to GR. Knox (Stud Hist Philos Sci Part B Stud Hist Philos Mod Phys 42(4):264–275, 2011) claims that there is no genuine underdetermination between GR and TEGR; we call this verdict into question by isolating and addressing her individual arguments. In addition, we anticipate and evaluate two further worries for realism about the torsionful spacetimes of TEGR, which we call the ‘problem of operationalisability’ and the ‘problem of visualisability’. [ABSTRACT FROM AUTHOR]

The cochlea, situated within the inner ear, is a spiral-shaped, liquid-filled organ responsible for hearing. The physiological significance of its shape remains uncertain. Previous research has scarcely addressed the occurrence of transverse flow within the cochlea, particularly in relation to its unique shape. This study aims to investigate the impact of the geometric features of the cochlea on fluid dynamics by characterizing transverse flow induced by harmonically oscillating axial flow in square ducts with curvature and torsion resembling human cochlear anatomy. We examined four geometries to investigate curvature and torsion effects on axial and transverse flow components. Twelve frequencies from 0.125 Hz to 256 Hz were studied, covering infrasound and low-frequency hearing, with mean inlet velocity amplitudes representing levels expected for normal conversation or louder situations. Our simulations show that torsion contributes significantly to transverse flow in unsteady conditions, and that its contribution increases with increasing oscillation frequency. Curvature alone has a small effect on transverse flow strength, which decreases rapidly with increasing frequency. Strikingly, the combined effect of curvature and torsion on transverse flow is greater than expected from a simple superposition of the two effects, especially when the relative contribution of curvature alone becomes negligible. These findings may be relevant to understanding physiological processes in the cochlea, including metabolite transport and wall shear stress. Further studies are needed to investigate possible implications for cochlear mechanics. [ABSTRACT FROM AUTHOR]

A tool for path following for a mobile manipulator is herein presented. The control algorithm is obtained by projecting a local frame associated with the robot onto the desired path, thus obtaining a non-orthogonal moving frame. The Serret–Frenet frame moving along the curve is considered as a reference. A curve resulting from the control points of a B-spline in 2D or 3D is investigated as the desired path. It is used to show how the geometric continuity of the path has an impact on the performance of the robot in terms of undesired force spikes. This can be understood by looking at the curvature and, in 3D, at the torsion of the path. These unwanted effects vanish and better performance is achieved thanks to the change of the B-spline order. The theoretical results are confirmed by the simulation study for a mobile manipulator consisting of a non-holonomic wheeled base coupled with a holonomic robotic arm with three degrees of freedom (rotational and prismatic). [ABSTRACT FROM AUTHOR]

In this paper, pedal-like curves are defined resulting from the orthogonal projection of a fixed point on the alternative frame vectors of a given regular curve. For each pedal curve, the Frenet vectors, the curvature and the torsion functions are found to provide the common relations among the main curve and its pedal curves. Then, Smarandache curves are defined by using the alternative frame vectors of each pedal curve as position vectors. The relations of the Frenet apparatus are also established for the pedal curves and their corresponding Smarandache curves. Finally, the expressions of the alternative frame apparatus of each Smarandache curves are given in terms of the alternative frame elements of the pedal curves. Thus, a set of new symmetric curves are introduced that contribute to the vast curve family. [ABSTRACT FROM AUTHOR]

In this study, first the pedal curves as the geometric locus of perpendicular projections to the Frenet vectors of a space curve were defined and the Frenet vectors, curvature, and torsion of these pedal curves were calculated. Second, for each pedal curve, Smarandache curves were defined by taking the Frenet vectors as position vectors. Finally, the expressions of Frenet vectors, curvature, and torsion related to the main curves were obtained for each Smarandache curve. Thus, new curves were added to the curve family. [ABSTRACT FROM AUTHOR]

We introduce the notion of conformal trajectories in three-dimensional Riemannian manifolds M3. Given a conformal vector field V ∈ 픛(M3), a conformal trajectory of V is a regular curve γ in M3 satisfying ∇γ′γ′ = qV × γ′, for some fixed nonzero constant q ∈ ℝ. In this paper, we study the conformal trajectories in the space forms ℝ3, 핊3 and ℍ3. For (non-Killing) conformal vector fields in 핊3 (respectively, in ℍ3), we prove that conformal trajectories have constant curvature and its torsion is a linear combination of trigonometric (respectively, hyperbolic) functions on the arc-length parameter. In the case of Euclidean space ℝ3, we obtain the same result for the radial vector field and characterizing all conformal trajectories. [ABSTRACT FROM AUTHOR]

It has been a widely-accepted belief that for a planar convex domain with two coordinate axes of symmetry, the location of maximal norm of gradient of torsion function is either linked to contact points of largest inscribed circle or connected to points on boundary of minimal curvature. However, we show that this is not quite true in general. Actually, we derive the precise formula for the location of maximal norm of gradient of torsion function on nearly ball domains in ℝn, which displays nonlocal nature and thus does not inherently establish a connection to the aforementioned two types of points. Consequently, explicit counterexamples can be straightforwardly constructed to illustrate this deviation from conventional understanding. We also prove that for a rectangular domain, the maximum of the norm of gradient of torsion function exactly occurs at the centers of the faces of largest (n - 1)-volume. [ABSTRACT FROM AUTHOR]

In this paper, we present a geometric perspective on how to quantify the bending and the twisting of quantum curves traced by state vectors evolving under nonstationary Hamiltonians. Specifically, relying on the existing geometric viewpoint for stationary Hamiltonians, we discuss the generalization of our theoretical construct to time-dependent quantum-mechanical scenarios where both time-varying curvature and torsion coefficients play a key role. Specifically, we present a quantum version of the Frenet–Serret apparatus for a quantum trajectory in projective Hilbert space traced out by a parallel-transported pure quantum state evolving unitarily under a time-dependent Hamiltonian specifying the Schrödinger evolution equation. The time-varying curvature coefficient is specified by the magnitude squared of the covariant derivative of the tangent vector | T 〉 to the state vector | Ψ 〉 and measures the bending of the quantum curve. The time-varying torsion coefficient, instead, is given by the magnitude squared of the projection of the covariant derivative of the tangent vector | T 〉 to the state vector | Ψ 〉 , orthogonal to | T 〉 and | Ψ 〉 and, in addition, measures the twisting of the quantum curve. We find that the time-varying setting exhibits a richer structure from a statistical standpoint. For instance, unlike the time-independent configuration, we find that the notion of generalized variance enters nontrivially in the definition of the torsion of a curve traced out by a quantum state evolving under a nonstationary Hamiltonian. To physically illustrate the significance of our construct, we apply it to an exactly soluble time-dependent two-state Rabi problem specified by a sinusoidal oscillating time-dependent potential. In this context, we show that the analytical expressions for the curvature and torsion coefficients are completely described by only two real three-dimensional vectors, the Bloch vector that specifies the quantum system and the externally applied time-varying magnetic field. Although we show that the torsion is identically zero for an arbitrary time-dependent single-qubit Hamiltonian evolution, we study the temporal behavior of the curvature coefficient in different dynamical scenarios, including off-resonance and on-resonance regimes and, in addition, strong and weak driving configurations. While our formalism applies to pure quantum states in arbitrary dimensions, the analytic derivation of associated curvatures and orbit simulations can become quite involved as the dimension increases. Thus, finally we briefly comment on the possibility of applying our geometric formalism to higher-dimensional qudit systems that evolve unitarily under a general nonstationary Hamiltonian. [ABSTRACT FROM AUTHOR]

It is known that the Frenet–Serret apparatus of a space curve in three-dimensional Euclidean space determines the local geometry of curves. In particular, the Frenet–Serret apparatus specifies important geometric invariants, including the curvature and the torsion of a curve. It is also acknowledged in quantum information science that low complexity and high efficiency are essential features to achieve when cleverly manipulating quantum states that encode quantum information about a physical system. In this paper, we propose a geometric perspective on how to quantify the bending and the twisting of quantum curves traced by dynamically evolving state vectors. Specifically, we propose a quantum version of the Frenet–Serret apparatus for a quantum trajectory in projective Hilbert space traced by a parallel-transported pure quantum state evolving unitarily under a stationary Hamiltonian specifying the Schrödinger equation. Our proposed constant curvature coefficient is given by the magnitude squared of the covariant derivative of the tangent vector | T 〉 to the state vector | Ψ 〉 and represents a useful measure of the bending of the quantum curve. Our proposed constant torsion coefficient, instead, is defined in terms of the magnitude squared of the projection of the covariant derivative of the tangent vector | T 〉 , orthogonal to both | T 〉 and | Ψ 〉. The torsion coefficient provides a convenient measure of the twisting of the quantum curve. Remarkably, we show that our proposed curvature and torsion coefficients coincide with those existing in the literature, although introduced in a completely different manner. Interestingly, not only we establish that zero curvature corresponds to unit geodesic efficiency during the quantum transportation in projective Hilbert space, but we also find that the concepts of curvature and torsion help enlighten the statistical structure of quantum theory. Indeed, while the former concept can be essentially defined in terms of the concept of kurtosis, the positivity of the latter can be regarded as a restatement of the well-known Pearson inequality that involves both the concepts of kurtosis and skewness in mathematical statistics. Finally, not only do we present illustrative examples with nonzero curvature for single-qubit time-independent Hamiltonian evolutions for which it is impossible to generate torsion, but we also discuss physical applications extended to two-qubit stationary Hamiltonians that generate curves with both nonzero curvature and nonvanishing torsion traced by quantum states with different degrees of entanglement, ranging from separable states to maximally entangled Bell states. In the Appendix C, we examine the different curvature and torsion characteristics of the three qubit | GHZ 〉 and | W 〉 states under evolution by a quantum Heisenberg Hamiltonian. [ABSTRACT FROM AUTHOR]

We study curve-shortening flow for twisted curves in $\mathbb {R}^3$ (that is, curves with nowhere vanishing curvature $\kappa $ and torsion $\tau $) and define a notion of torsion-curvature entropy. Using this functional, we show that either the curve develops an inflection point or the eventual singularity is highly irregular (and likely impossible). In particular, it must be a Type-II singularity which admits sequences along which ${\tau }/{\kappa ^2} \to \infty $. This contrasts strongly with Altschuler's planarity theorem, which shows that ${\tau }/{\kappa } \to 0$ along any essential blow-up sequence. [ABSTRACT FROM AUTHOR]

One of the most relevant topics in web theory is linearization. A particular class of linearizable webs is the Grassmannizable web. Akivis gave a characterization of such a web, showing that Grassmannizable webs are equivalent to isoclinic and transversally geodesic webs. The obstructions given by Akivis that characterize isoclinic and transversally geodesic webs are computed locally, and it is difficult to give them an interpretation in relation to torsion or curvature of the unique Chern connection associated with a web. In this paper, using Nagy's web formalism, Frölisher—Nejenhuis theory for derivation associated with vector differential forms, and Grifone's connection theory for tensorial algebra on the tangent bundle, we find invariants associated with almost-Grassmann structures expressed in terms of torsion, curvature, and Nagy's tensors, and we provide an interpretation in terms of these invariants for the isoclinic, transversally geodesic, Grassmannizable, and parallelizable webs. [ABSTRACT FROM AUTHOR]

We introduce and study a deformation of the geodesic curvature for a given spherical curve γ . Also, we define a new type of evolute and two Fermi-Walker type derivatives for γ . Some concrete examples are detailed with a special attention towards space curves with a constant torsion. [ABSTRACT FROM AUTHOR]

The construction of new railway lines is based on the railway plan. There are various ways to draw up a railway plan. The basis of all railway plans is a scheme of geometric point locations, the projection of the center of gravity of the carriage is on a horizontal plane and consists of a single flat line. The railway plan consists of linear and curved parts connecting straight sections. However, the curves determining the position of the rails of the railway track in the curved part will be spatial. To extinguish the centrifugal force arising in the curved part of the road, an external rail rises. In this case, the elevated curve representing the outer rail becomes spatial. Therefore, in the work, it is proposed to draw up a plan of a railway track as two curves, one of which is flat, and the other depicts an external spatial rail. In this case, the distance between the ends of the rectilinear parts and the angle between the rectilinear parts are selected as the main parameters. In the work, for the simplest case, when both linear parts belong to the same horizontal plane, it is proved that the curved part is a spatial curve. The curvature of the required curve was determined and a dynamic system was constructed, the solution of which would be a curve that satisfied the technical conditions presented for the railway route. This dynamic system is proposed as a mathematical model of the railway route. In the rectilinear parts, the railway plan is straight on a horizontal plane. The curve of the road should be spatial.

Poincaré Gauge Theories are a class of Metric-Affine Gravity theories with a metric-compatible (i.e. Lorentz) connection and with an action quadratic in curvature and torsion. We perform an explicit one-loop calculation starting with a single term of each type and show that not only are all other terms generated, but also many others. In our particular model all terms containing torsion are redundant and can be eliminated by field redefinitions, but there remains a new term quadratic in curvature, making the model non-renormalizable. We discuss the likely behavior of more general theories of this type. [ABSTRACT FROM AUTHOR]

In this paper, firstly, we define the evolute curve of any curve concerning the vertical, complete, and horizontal lifts on space R³ to its tangent space TR³ = R6. Secondly, we examine the Frenet-Serret apparatus (T*(s), N*(s), B*(s), κ", τ") and the Darboux vector W of the evolute curve a according to the vertical, complete and horizontal lifts on TR³ by depend on the lifting of Frenet-Serret aparatus {T(s), N(s), B(s), K, T} of the first curve a on space R³. In addition, we include all special cases the curvature k*(s) and torsion t(s) of the Frenet-Serret aparatus (T" (s), N(s), B(s), κ, τ"} of the evolute curve a with respect concerning complete and horizontal lifts on space R³ to its tangent space TR³. As a result of this transformation on space R³ to its tangent space TR³, we could have some information about the features of the volute curve of any curve on space TR3 by looking at the characteristics of the first curve a. Moreover, we get the transformation of the evolute curves using bifts on R³ to tangent space TR³. Finally, some examples are given for each curve transformation to validate our theoretical claims. [ABSTRACT FROM AUTHOR]

In this work, we consider geometrical models describing spinning particles in the context of generalized Robertson–Walker spacetimes. We study spacelike and timelike trajectories for massive and massless particles governed by two different Lagrangians: one depending on the torsion and the other on the curvature of the trajectory. For both, we are able to relate the curvature and torsion of such trajectories with the curvature of the spatial fiber of the cosmological model. Moreover, several conserved quantities are described as well as their possible relations with physical parameters of the particle. [ABSTRACT FROM AUTHOR]

We study a class of early universe cosmological models based on Einstein–Cartan gravity and including a higher derivative term corresponding to a power of the Holst scalar curvature. The resulting effective action is basically given by General Relativity and an additional neutral pseudoscalar field (the pseudoscalaron), unequivocally related to the corresponding components of the torsion, that necessarily acquire a dynamics. The induced pseudoscalaron potential provides a realistic inflationary phase together with a very rich postinflationary epoch, resulting from the coupling of the pseudoscalaron to ordinary matter. [ABSTRACT FROM AUTHOR]

An important role in the roads design is played by plane curves, if the road lies on a plane surface and by space curves, if the road can not be embeded in a plane. This article presents some work done in the two and three dimensional roads design, by using the differential geometry methods. A study of a general case for plane roads is given.

This study explores the problem of describing viscous fluid motion for Navier–Stokes equations in curved channels, which is important in applications like hemodynamics and pipeline transport. Channel curvature leads to vortex flows and closed vortex zones. Asymptotic models of the flux problem are useful for describing viscous fluid motion in long pipes, thus considering geometric parameters like pipe diameter and characteristic length. This study provides a representation for the vorticity vector and energy dissipation in the flow problem for a curved channel, thereby determining the magnitude of vorticity and energy dissipation depending on the channel's central line curvature and torsion. The accuracy of the asymptotic formulas are estimated in terms of small parameter powers. Numerical calculations for helical tubes demonstrate the effectiveness of the asymptotic formulas. [ABSTRACT FROM AUTHOR]

We consider homogeneous and isotropic cosmological models in the framework of three geometrical theories of gravitation. In Einstein's general relativity, they are given in terms of the curvature of the Levi-Civita connection in torsion-free metric spacetimes; in the teleparallel equivalent of general relativity, they are given in terms of the torsion of flat metric spacetimes; and in the symmetric teleparallel equivalent of general relativity, they are given in terms of the nonmetricity of flat torsion-free spacetimes. We argue that although these three formulations seem to be different, the corresponding cosmological models are in fact equivalent and their choice is conventional. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the effect of the curvature and torsion of the ear canal on its resonance through a comparison between several ear canal models. Utilizing Stinson's ear canal geometries as a reference, we build and analyze several ear canal models using both transmission matrix and numerical methods for the purpose of comparative assessment. A conical transmission unit, which considers visco-thermal effects, is employed for the modeling of the human ear canal. While the transfer matrix and numerical method agree well for a straight axis model, this simplification results in up to 20% deviation from a curved canal. We propose the curve twist ratio as a metric to quantify the influence of curvature on the ear canal and find that our proposed metric can effectively express the error introduced by the simplified straight axis model. Upon this metric, an empirical equation is proposed for incorporating the curvature effect in the transmission matrix method, enabling it to generate comparable results to those of the numerical method, which considers the effect of the curvature and torsion, thus dramatically accelerating computation. [ABSTRACT FROM AUTHOR]

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In the conventional formulation of general relativity, gravity is represented by the metric curvature of Riemannian geometry. There are also alternative formulations in flat affine geometries, wherein the gravitational dynamics is instead described by torsion and nonmetricity. These so-called general teleparallel geometries may also have applications in material physics, such as the study of crystal defects. In this work, we explore the general teleparallel geometry in the language of differential forms. We discuss the special cases of metric and symmetric teleparallelisms, clarify the relations between formulations with different gauge fixings and without gauge fixing, and develop a method of recasting Riemannian into teleparallel geometries. As illustrations of the method, exact solutions are presented for the generic quadratic theory in 2, 3 and 4 dimensions. [ABSTRACT FROM AUTHOR]

In this article we have characterized the natural lift curve of a curve in IR³ according to its torsion and curvature. The natural lift curve of a timelike curve in IR³1 is characterized by the torsion and curvature of the natural lift curve, taking into account whether it is a spacelike curve with a timelike binormal or a spacelike curve with a space binormal. The natural lift curve of a spacelike curve with a timelike binormal in IR³1 is characterized according to the torsion and curvature of the natural lift curve, considering that the natural lift curve is a spacelike curve with a timelike binormal or a spacelike curve with a space binormal. [ABSTRACT FROM AUTHOR]

The minimal length conjecture is merged with a generalized quantum uncertainty formula, where we identify the minimal uncertainty in a particle's position as the minimal measurable length scale. Thus, we obtain a quantum-induced deformation parameter that directly depends on the chosen minimal length scale. This quantum-induced deformation is conjectured to require the generalization of Riemannian spacetime geometry underlying the classical theory of general relativity to an eight-dimensional spacetime fiber bundle, which dictates the deformation of the line element, metric tensor, Levi-Civita connection, Riemann curvature tensor, etc. We calculate the deformation thus produced in the Levi-Civita connection and find it to explicitly and exclusively depend on the product of the minimum measurable length and the particle's spacelike four-acceleration vector, L 2 x ¨ 2 . We find that the deformed Levi-Civita connection preserves all properties of its undeformed counterpart, such as torsion freedom and metric compatibility. Accordingly, we have constructed a deformed version of the Riemann curvature tensor whose expression can be factorized in all its terms with different functions of L 2 x ¨ 2 . We also show that the classical four-manifold status of being Riemannian is preserved when the quantum-induced deformation is negligible. We study the dependence of a parallel-transported tangent vector on the spacelike four-acceleration. We illustrate the impact of the minimal-length-induced quantum deformation on the classical geometrical objects of the general theory of relativity using the unit radius two-sphere example. We conclude that the minimal length deformation implies a correction to the spacetime curvature and its contractions, which is manifest in the additional curvature terms of the corrected Riemann tensor. Accordingly, quantum-induced effects endow an additional spacetime curvature and geometrical structure. [ABSTRACT FROM AUTHOR]

In this study, we consider DNA as a torus knot that is formed by an elastic string. In order to determine what kinds of knot could be formed, we present its energy spectrum by combining Euler rotation, DNA's mechanical properties, and the modified Faddeev–Skyrme model. Our results theoretically demonstrated that the flexural rigidity of DNA plays an important role. If it is smaller than a critical value, DNA is likely to form a coiled structure. Conversely, above the critical value, DNA forms a twisting structure. The energy spectrum provides a way to identify the types of knots that are most likely to be created by DNA, according to the principle of energy minimisation, and with implications for its functional and packaging states in the cell nucleus. [ABSTRACT FROM AUTHOR]

Most small SUVs in the automotive market are equipped with torsion beam suspension for the rear wheels. Torsion beam suspension consists of a cross-member and a trailing arm. The cross-member plays a crucial role in preventing the vehicle from twisting; therefore, a shape that can withstand loads is essential. In this study, various shapes of cross-member reinforcements were added to the existing torsion beam suspension to analyze its structural strength when subjected to arbitrary forces. Analysis results were obtained for stiffness and driving stability factors such as smooth road shake, impact hardness, and memory shake. Based on these results, we identified the optimal cross-member shape with low torsional stiffness and a small side view swing arm angle by examining the changes in driving stability. [ABSTRACT FROM AUTHOR]

In this paper, it has been researched curves lying on parallel-like surfaces Mf of the ruled surface M in E³. Using the definition of parallel-like surfaces it has been found parametric expressions of parallel-like surface of the ruled surface and image curve of the directrix curve of the base surface. Moreover, obtaining Darboux frames of curves lying on surfaces M and Mf, it has been compared the geodesic curvatures, the normal curvatures and the geodesic torsions of these curves. [ABSTRACT FROM AUTHOR]

In this paper, we define and study the differential geometry of curves of constant breadth in a Walker 4-manifold and we construct an example of curves of constant breadth in this manifold. [ABSTRACT FROM AUTHOR]

We consider the class of compact Hermitian manifolds whose Chern connection is Ambrose-Singer, namely, it has parallel torsion and curvature. We prove structure theorems for such manifolds. [ABSTRACT FROM AUTHOR]

In this paper, a Riemannian geometry of noncommutative super surfaces is developed which generalizes [4] to the super case. The notions of metric and connections on such noncommutative super surfaces are introduced and it is shown that the connections are metric-compatible and have zero torsion when the super metric is symmetric, giving rise to the corresponding super Riemann curvature. The latter also satisfies the noncommutative super analogue of the first and second Bianchi identities. We also give some examples and study them in details. [ABSTRACT FROM AUTHOR]

In this paper, we focus on the research and analysis of the geometric properties and symmetry of slant curves and contact magnetic curves in Lorentzian α -Sasakian 3-manifolds. To do this, we define the notion of Lorentzian cross product. From the perspectives of the Legendre and non-geodesic curves, we found the ratio relationship between the curvature and torsion of the slant curve and contact magnetic curve in the Lorentzian α -Sasakian 3-manifolds. Moreover, we utilized the property of the contact magnetic curve to characterize the manifold as Lorentzian α -Sasakian and to find the slant curve type of the Frenet contact magnetic curve. Furthermore, we found an example to verify the geometric properties of the slant curve and contact magnetic curve in the Lorentzian α -Sasakian 3-manifolds. [ABSTRACT FROM AUTHOR]

We study two natural problems concerning the scalar and the Ricci curvatures of the Bismut connection. Firstly, we study an analog of the Yamabe problem for Hermitian manifolds related to the Bismut scalar curvature, proving that, fixed a conformal Hermitian structure on a compact complex manifold, there exists a metric with constant Bismut scalar curvature in that class when the expected constant scalar curvature is non-negative. A similar result is given in the general case of Gauduchon connections. We then study an Einstein-type condition for the Bismut Ricci curvature tensor on principal bundles over Hermitian manifolds with complex tori as fibers. Thanks to this analysis, we construct explicit examples of Calabi–Yau with torsion Hermitian structures and prove a uniqueness result for them. [ABSTRACT FROM AUTHOR]

The modified orthogonal frame is an important tool to study analytic space curves whose curvatures have discrete zero points. In this article, by using the modified orthogonal frame, Mannheim curves and their partner curves are investigated in Minkowski 3-space. Some characterizations according to the curvatures and torsions of the curves are given. Finally, some relations under the conditions for Mannheim curves and their partner curves to be generalized helices are presented. All the possible cases for the partner curves to be spacelike and timelike are considered in the whole of the article.

We continue to study the space of centered planes in projective space . In this paper, we use E. Cartan's method of external forms and the group-theoretical method of G. F. Laptev to study the space of centered planes of the same dimension. These methods are successfully applied in physics. In a generalized bundle, a bilinear connection associated with a space is given. The connection object contains two simplest subtensors and subquasi-tensors (four simplest and three simple subquasi-tensors). The object field of this connection defines the objects of torsion, curvature-torsion, and curvature. The curvature tensor contains six simplest and four simple subtensors, and curvature-torsion tensor contains three simplest and two simple subtensors. The canonical case of a generalized bilinear connection is considered.

We study a special class of Finsler metrics which we refer to as Almost Rational Finsler metrics (shortly, AR-Finsler metrics). We give necessary and sufficient conditions for an AR-Finsler manifold (M, F) to be Riemannian. The rationality of some Finsler geometric objects such as Cartan torsion, geodesic spray, Landsberg curvature and S-curvature is investigated. For a particular subfamily of AR-Finsler metrics we have proved that if F has isotropic S-curvature, then the S-curvature vanishes identically; if F has isotropic mean Landsberg curvature, then it is weakly Landsberg; if F is an Einstein metric, then it is Ricci-flat. Moreover, there exists no Randers AR-Finsler metric. Finally, we provide some nontrivial examples of AR-Finsler metrics. [ABSTRACT FROM AUTHOR]

In this paper, we define a nonlinear transformation between space curves which preserves the ratio of t/k of the given curve in 3-dimensional Euclidean space E³. We investigate invariant and associated curves of this transformation by the help of curvature and torsion functions of the base curve. Moreover, we define a new curve (family) so-called quasi-slant helix, and we obtain some characterizations in terms of the curvatures of this curve. Finally, we examine some curves in the kinematics, and give the pictures of some special curves and their images with respect to the transformation. [ABSTRACT FROM AUTHOR]

In this paper, we prove a conjecture raised by Angella, Otal, Ugarte and Villacampa recently, which states that if the Strominger connection (also known as Bismut connection) of a compact Hermitian manifold is Kähler-like, in the sense that its curvature tensor obeys all the symmetries of the curvature of a Kähler manifold, then the metric must be pluriclosed. What we actually showed is a bit more: for any given Hermitian manifold, the Strominger Kähler-like condition is equivalent to the pluriclosedness of the metric plus the parallelness of the torsion. [ABSTRACT FROM AUTHOR]

A natural connection with torsion is defined, and it is called the first natural connection on the Riemannian Π-manifold. Relations between the introduced connection and the Levi–Civita connection are obtained. Additionally, relations between their respective curvature tensors, torsion tensors, Ricci tensors, and scalar curvatures in the main classes of a classification of Riemannian Π-manifolds are presented. An explicit example of dimension five is provided. [ABSTRACT FROM AUTHOR]

Many theories of gravity are spoiled by strongly coupled modes: the high computational cost of Hamiltonian analysis can obstruct the identification of these modes. A computer algebra implementation of the Hamiltonian constraint algorithm for curvature and torsion theories is presented. These non-Riemannian or Poincaré gauge theories suffer notoriously from strong coupling. The implementation forms a package (the 'Hamiltonian Gauge Gravity Surveyor' – HiGGS) for the xAct tensor manipulation suite in Mathematica. Poisson brackets can be evaluated in parallel, meaning that Hamiltonian analysis can be done on silicon, and at scale. Accordingly HiGGS is designed to survey the whole Lagrangian space with high-performance computing resources (clusters and supercomputers). To demonstrate this, the space of 'outlawed' Poincaré gauge theories is surveyed, in which a massive parity-even/odd vector or parity-odd tensor torsion particle accompanies the usual graviton. The survey spans possible configurations of teleparallel-style multiplier fields which might be used to kill-off the strongly coupled modes, with the results to be analysed in subsequent work. All brackets between the known primary and secondary constraints of all theories are made available for future study. Demonstrations are also given for using HiGGS – on a desktop computer – to run the Dirac–Bergmann algorithm on specific theories, such as Einstein–Cartan theory and its minimal extensions. [ABSTRACT FROM AUTHOR]

We retreat the well-known Einstein–Cartan theory by slightly modifying the covariant derivative of spinor field by investigating double cover of the Lorentz group. We first write the Lagrangian consisting of the Einstein–Hilbert term, Dirac term and a scalar field term in a non-Riemannian spacetime with curvature and torsion. Then by solving the affine connection analytically we reformulate the theory in the Riemannian spacetime in a self-consistent way. Finally we discuss our results and give future perspectives on the subject. [ABSTRACT FROM AUTHOR]

This study explores the problem of describing viscous fluid motion for Navier–Stokes equations in curved channels, which is important in applications like hemodynamics and pipeline transport. Channel curvature leads to vortex flows and closed vortex zones. Asymptotic models of the flux problem are useful for describing viscous fluid motion in long pipes, thus considering geometric parameters like pipe diameter and characteristic length. This study provides a representation for the vorticity vector and energy dissipation in the flow problem for a curved channel, thereby determining the magnitude of vorticity and energy dissipation depending on the channel’s central line curvature and torsion. The accuracy of the asymptotic formulas are estimated in terms of small parameter powers. Numerical calculations for helical tubes demonstrate the effectiveness of the asymptotic formulas.

The paper discusses difference between super-elevation of recorded motion-trajectory (MT) curves and constant super-elevation of curve plane and demonstrates that vertical curvature used in railroad literature is not necessarily associated with curve out-of-plane bending or twist. Vertical curvature can be highly nonlinear while the curve remains planar and untwisted. A computational procedure is proposed for identifying MT planar curves using computer-simulation or experimentally recorded data. Data-driven science (DDS) approach allows measuring Frenet vertical-development and super-elevation that define centrifugal inertia force. Difference between motion-independent curve-plane and motion-dependent osculating plane (OP) which contains velocity, acceleration, and inertia centrifugal forces is explained. Three Frenet angles: horizontal-curvature, vertical-development, and bank angles; are used to define planar MT geometry. Zero-torsion and zero-vertical-curvature conditions are derived for identifying planar curves and demonstrating that vertical curvature is not always associated with curve torsion. An orthogonal transformation is used to define OP sweeping angle whose derivative defines curve curvature regardless of curve-plane orientation. Difference between Frenet horizontal-curvature angle and OP sweeping angle is discussed. It is shown that super-elevation of planar-curve surface is equal to Frenet super-elevation if Frenet vertical-development angle is zero. An analytical 3D, yet planar and untwisted, curve is used to demonstrate that planar curves can have non-vanishing and nonlinear curvature, vertical-elevation, vertical curvature, and super-elevation. [ABSTRACT FROM AUTHOR]

In formulation of beam-vibration equations, curvature of space curves is used to define the strain energy and elastic forces. Only in special cases, the curvature and torsion can be associated with derivatives of angles. Furthermore, curve twist is result of coupled in-plane and out-of-plane bending modes. While this mode coupling can be represented by two rotations, curve curvature or torsion cannot, in general, be associated with single rotation. Curvature and torsion, in their most general forms, are defined using skew-symmetric Cartan matrix, which leads to the Serret-Frenet equations. This paper uses two different sequences of rotation to discuss exact differentiability of curvature and torsion and demonstrate that curve torsion cannot, in general, be defined as derivative of uniquely-defined angle performed about curve tangent vector. Frenet angles are used to develop simple and general expressions for elements of curve Cartan matrix. The analysis and results presented show the fundamental difference between Bishop shear angle, which is not unique and does not enter into definition of curve geometry; and Frenet bank angle, which is unique and enters into definition of curve geometry. [ABSTRACT FROM AUTHOR]

In this paper, we study a long existing open problem on Landsberg metrics in Finsler geometry. For this aim, we study the Landsberg curvature of three-dimensional homogeneous Finsler manifolds. First, we express the second Matsumoto torsion of three-dimensional Finsler manifolds, explicitly. Then, we show that the mean Landsberg curvature of three-dimensional homogeneous Finsler manifolds satisfy an ODE. Finally, we prove that every homogeneous 3-dimensional L-reducible Finsler manifold has constant relatively isotropic mean Landsberg curvature if and only if it is a Landsberg metric or a Randers metric of Berwald-type. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the properties of curves of constant breadth in a strict Walker 3-manifold and we construct examples of curves of constant breadth. [ABSTRACT FROM AUTHOR]

Considering a non-symmetric linear connection and its dual one appear 6 independent curvature tensors [15]. In the present paper we study properties of curvature tensors of semi-symmetric metric connections on a generalized Riemannian manifold. It is shown that if linear connection preserves the symmetric part of the generalized Riemannian metric with semi-symmetric torsion with an appropriate additional condition, then these six curvature tensors can be expressed by linear combination of Weyl conformal curvature tensor, Weyl projective curvature tensor and the concircular curvature tensor. In the case of the curvature tensor , we have proved that if exists a linear connection preserving the symmetric part of the generalized Riemannian metric with semi-symmetric torsion, whose curvature tensor vanishes, it is necessary and sufficient that the Riemannian metric be projectively flat. For tensor we also get a useful result. If exists a linear connection preserving the symmetric part of the generalized Riemannian metric with semi-symmetric torsion, whose curvature tensor and Ricci tensor vanish, it is necessary and sufficient that the Riemannian metric be conformally flat. [ABSTRACT FROM AUTHOR]

We prove that in a Finsler manifold with vanishing χ -curvature (in particular with constant flag curvature) some non-Riemannian geometric structures are geodesically invariant and hence they induce a set of non-Riemannian first integrals. Two alternative expressions of these first integrals can be obtained either in terms of the mean Berwald curvature, or as functions of the mean Cartan torsion and the mean Landsberg curvature. [ABSTRACT FROM AUTHOR]

The article considers two graph-analytical algorithms. The first algorithm makes it possible to form a spatial curve passing through given nodal points with direction vectors specified at these points. The second algorithm allows you to generate a flat compound curve passing through the given nodal points with direction vectors and curvature radii specified at these points. The constructed curves are formed by cubic Bezier segments. Direction vectors are treated as a control for the shape of the curve being constructed. At the nodal points, second-order geometric smoothness is ensured, due to the continuity of the slope and curvature. A distinctive feature of the proposed algorithms is the significant use of constructive means of computer graphics.