Tag Info

5

The symmetrizer $S: \bigotimes^k V \to \bigotimes^k V$ is idempotent. Hence, $\ker(S) = \mathrm{im}(\mathrm{id}-S)$. This is generated by elements of the form $\alpha-{}^\sigma \alpha$, where $\sigma$ is some permutation.

3

Well, you're correct, in some sense, the cross-product of two vectors is not really a vector of the same type. The language used to distinguish the two types is: polar vectors: flip sign of component under coordinate inversion axial vectors: do not flip sign of component under inversion (also known as pseudovector see this wikipedia article) All of this ...

2

You'd best think of the cross product by first defining the following: Let $\varepsilon:\mathbb{R}^3\times\mathbb{R}^3\times\mathbb{R}^3\rightarrow\mathbb{R}$ be a (0,3)-type tensor that is totally antisymmetric. Such tensors form a one-dimensional subspace within the space of (0,3)-type tensors, therefore any such tensor (except the zero tensor) differ ...

2

It cannot be that $f'(s\otimes t) = (f(s),f(t))$ because on one hand $f$ isn't necessarily defined on $T$ (as a polynomial function), while on the other hand $(f(s),f(t))$ isn't an element of $S \otimes T$. Now, note that there is a natural map $S \to S \otimes T$, namely $s \mapsto s \otimes 1$. Thus if $f \in S[X]$ is $$f(X) = a_n X^n + a_{n-1}X^{n-1} + ... 2 SECTION A : The linearly independent elements of a Totally Symmetric Tensor \;T_{i_{1}i_{2}\cdots i_{p-1}i_{p}}\;(important for the interpretation of Quark Theory of Baryons in Particle Physics) \begin{equation*} \bbox[#FFFF88,8px] {\boldsymbol{3}\boldsymbol{\otimes}\boldsymbol{3}\boldsymbol{\otimes}\boldsymbol{3}= ... 2 If the Riemannian curvature tensor takes this form, then at any given point all the sectional curvatures are equal. Thus if n>2 then Schur's Lemma tells us that the sectional curvature is in fact constant; i.e. k must be constant. If n=2 then this is the problem of prescribed Gauss curvature, which you should be able to find many papers about. 2 Your problem is \delta_{bd}\ \delta^{bd}=\delta^b_b=\mathrm{Tr}(\mathrm{Id_3})=3, not one. 2 First note that every vector bundle E gives you C^{\infty}(M)-Module structure on global sections \Gamma(E). Additionaly for vector bundles E,F on maniflod M there are C^{\infty}(M)-Module isomorphism$$\Gamma(E)\otimes_{C^{\infty}(M)}\Gamma(F)\simeq\Gamma(E\otimes_{\mathbb{R}} ...

2

I am going to suppose that by affine transformation you mean a mapping from $T : V \to V$ from a vector space to itself s.t. $$T(x) = Ax + b$$ where $A : V \to V$ is a linear map, and $b$ is an element of the vector space. If that is the case, then no $T$ is not a tensor. A tensor needs to be a linear map on the tangent space of each point of the space on ...

1

The isotropic part is the one that you can represent with a scalar. The condition is that the rest is traceless. Isotropic in physics means independent on the direction, which is exactly the condition that it acts on every vector equally. So, $$A_{ij}v_j=av_i$$ for every $v_j$ simply means $A_{ij}=a\delta_{ij}$. You actually already wrote down the solution ...

1

The oriented volume spanned by three vectors is a multilinear alternating map of the vectors themselves. That's the starting point. See, e.g., the book by S.Winitzki.

1

Multiply by $g^{\sigma\tau}$ and use that $$g^{ab}g_{bc} = \delta^a_c,$$ so the right-hand side becomes $d^{\sigma}$, which is what you want. I'll leave the left-hand side to you, since you don't say if you mind raising the index on $A_{\mu\nu\tau}$.

1

Here, $i$ is, if you like, the index corresponding to the direction of the covariant derivative. More precisely, for, say, a $1$-form $\eta$, $\nabla_i \eta_j$ is the abstract index notation for denotes the $2$-tensor $\nabla \eta$ defined by $$(\nabla \eta)(X, Y) := (\nabla_X \eta)(Y).$$ Indeed, in abstract index notation this quantity is \$\nabla_i \eta_j ...

Only top voted, non community-wiki answers of a minimum length are eligible