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In this paper, we study a class of Finsler metrics called general $$(\alpha ,\beta )$$ -metrics, which are defined by a Riemannian metric and a 1-form. These metrics form a rich class of Finsler metrics. Suppose that $$F=\alpha \phi (b^{2},s)$$ is a general $$(\alpha ,\beta )$$ -metric which is conformally related to $$\tilde{F}=e^{\sigma (x)}F,$$ where $$\sigma := \sigma (x)$$ is a scalar function on M. We show that if F is Douglas metric, then $$\tilde{F}$$ is also Douglas metric if and only if the conformal transformation is a homothety under suitable condition on $$\phi $$ . Furthermore, we have investigated the conformal transformation of isotropic S-curvature general $$(\alpha ,\beta )$$ -metrics.

In this paper, we study $$\Xi $$ -curvature and H-curvature of a special class of Finsler metrics called general $$(\alpha ,\beta )$$ -metrics. We prove that every general $$(\alpha ,\beta )$$ -metric of almost vanishing H-curvature is of almost vanishing $$ \Xi $$ -curvature under certain conditions. Moreover, we study such Finsler metric with vanishing $$\Xi $$ -curvature and its interaction to the flag curvature.

Finsler metrics of quadratic curvatures form a rich and important class of metrics. In this paper, we study spherically symmetric metrics of quadratic curvatures. We find equations that characterize R-quadratic spherically symmetric Finsler metrics. In addition, we find the necessary and sufficient conditions for the metrics to be W-quadratic and Ricci-quadratic types.

Projective Ricci curvature is a projective invariant quantity in Finsler geometry which is introduced by Z. Shen. In this paper, we study special projective Ricci curvature of C-reducible Finsler metrics. The necessary and sufficient conditions of these metrics, which cause these metrics to be weak or isotropic projective Ricci curvature, are found and it is proved that C-reducible Douglas metric of isotropic PRic-curvature must be PRic flat. The same theorem for C-reducible metrics of scalar flag curvature is also investigated.

In this paper, we investigate the flag curvature of a special class of Finsler metrics called general spherically symmetric Finsler metrics, which are defined by a Euclidean metric and two related 1-forms. We find equations to characterize the class of metrics with constant Ricci curvature (tensor) and constant flag curvature. Moreover, we study general spherically symmetric Finsler metrics with the vanishing non-Riemannian quantity χ-curvature. In particular, we construct some new projectively flat Finsler metrics of constant flag curvature.

The local structure of Finsler metrics of constant flag curvature have been historically mysterious. It is proved that every Matsumoto metric of constant flag curvature on a closed n-dimensional manifold of dimension n ≥ 3 is either Riemannian or locally Minkowskian.

It is proved that a Randers metric F = α + β on a manifold of dimension n ⩾ 3 is projective if and only if the Lie algebra of projective vector fields p ( M , F ) has (locally) dimension n ( n + 2 ) . This can be regarded as an analogue of the corresponding result in Riemannian geometry.

The collection of all projective vector fields on a Finsler space $(M, F)$ is a finite-dimensional Lie algebra with respect to the usual Lie bracket, called the projective algebra denoted by $p(M,F)$ and is the Lie algebra of the projective group $P(M,F)$. The projective algebra $p(M,F=\alpha+\beta)$ of a Randers space is characterized as a certain Lie subalgebra of the projective algebra $p(M,\alpha)$. Certain subgroups of the projective group $P(M,F)$ and their invariants are studied. The projective algebra of Randers metrics of constant flag curvature is studied and it is proved that the dimension of the projective algebra of Randers metrics constant flag curvature on a compact $n$-manifold either equals $n(n+2)$ or at most is $\frac{n(n+1)}{2}$.

In this paper, we study projective algebra, p(M, F), of special (α, β)-metrics. The projective algebra of a Finsler space is a finite-dimensional Lie algebra with respect to the usual Lie bracket. We characterize p(M, F) of Matsumoto and square metrics of isotropic S-curvature of dimension n ≥ 3 as a certain Lie sub-algebra of the Killing algebra k(M, α). We also show that F has a maximum projective symmetry if and only if F either is a Riemannian metric of constant sectional curvature or locally Minkowskian.