Read e-book online A Characterization of a Class of [Z] Groups Via Korovkin PDF

# Read e-book online A Characterization of a Class of [Z] Groups Via Korovkin PDF

By Agrawal M.R., Tewari U.B.

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Extra resources for A Characterization of a Class of [Z] Groups Via Korovkin Theory

Example text

The cotangent bundle T ∗ M = x∈M Tx∗ M is also a 2n-dimensional manifold. A one-form ω : M → T ∗ M is a smooth map assigning to each x ∈ M a covector ω(x) ∈ T ∗ M . In local coordinates ω(x) = ωi (x)dxi |x or simply ω = ωi dxi . The diﬀerential of a map. If τ : M → N is a smooth map between two manifolds then its diﬀerential dτ : T M → T N is a linear map deﬁned pointwise for ﬁxed x as follows: let w ∈ Tx M be an arbitrary vector and h : N → R an arbitrary smooth function. Then a new vector (dτ w)|τ (x) ∈ Tτ (x)N is deﬁned by (dτ w)|τ (x) h := w(h ◦ τ )(x).

On Tx M the tensor g induces a scalar product v·w = g|x (v, w), and likewise for vector-ﬁelds. By forming the inverse matrix g ij (x) one deﬁnes a (2, 0)-tensor ﬁeld g ij ∂xi ⊗ ∂xj . Raising and lowering indices. Type conversion. g. if v = aij dxi ⊗ dxj is a (0, 2)-tensor-ﬁeld then cij = g il alj deﬁnes the coeﬃcients of a (1, 1)-tensor C = cij ∂xi ⊗ dxj . This operation is called raising an index. Similarly, indices can be lowered by multiplication with gij . Covariant diﬀerentiation, Christoﬀel symbols.

The graph of such a function u is a subset of M × Rk . The total space M × Rk is an (n + k)-dimensional smooth manifold. Each tangent space has the simple structure T(x,u) (M × Rk ) = Tx M × Rk . Vector ﬁelds w on M × Rk are written in local coordinates as w = ξ i (x, u)∂xi + φα (x, u)∂uα . We use the notation w = ξ(x, u) + φ(x, u) with ξ(x, u) ∈ Tx M and φ(x, u) = (φ1 (x, u), . . , φk (x, u)) ∈ Rk . Partial derivatives Consider a smooth function f : M × Rk → R. Partial derivatives of f are deﬁned as follows: for ﬁxed x partial derivatives of the function f (x, ·) : Rk → R with respect to uα , α = 1, .