Math Problem Statement

Solve this using basis vectors and basis dyadics

Solve this using basis vectors and basis dyadics

Solution

To solve uTTu\mathbf{u} \cdot \mathbf{T} - \mathbf{T}^\top \cdot \mathbf{u} using basis vectors and basis dyadics, we will expand it step-by-step.

Step 1: Represent the Vectors and Tensors in Basis Form

Let:

  • u\mathbf{u} be a vector represented as u=uiei\mathbf{u} = u_i \mathbf{e}_i in terms of its components uiu_i and the basis vectors ei\mathbf{e}_i.
  • T\mathbf{T} be a second-order tensor represented as T=Tijeiej\mathbf{T} = T_{ij} \mathbf{e}_i \otimes \mathbf{e}_j, where TijT_{ij} are its components in the basis.

The transpose of T\mathbf{T} is given by: T=Tjieiej\mathbf{T}^\top = T_{ji} \mathbf{e}_i \otimes \mathbf{e}_j

Step 2: Expand Each Term

  1. Term 1: uT\mathbf{u} \cdot \mathbf{T}: (uT)=uiei(Tjkejek)(\mathbf{u} \cdot \mathbf{T}) = u_i \mathbf{e}_i \cdot (T_{jk} \mathbf{e}_j \otimes \mathbf{e}_k) Using the dot product eiej=δij\mathbf{e}_i \cdot \mathbf{e}_j = \delta_{ij}, we simplify: (uT)=uiTijej(\mathbf{u} \cdot \mathbf{T}) = u_i T_{ij} \mathbf{e}_j

  2. Term 2: Tu\mathbf{T}^\top \cdot \mathbf{u}: (Tu)=(Tjieiej)ukek(\mathbf{T}^\top \cdot \mathbf{u}) = (T_{ji} \mathbf{e}_i \otimes \mathbf{e}_j) \cdot u_k \mathbf{e}_k Again, using the dot product, this becomes: (Tu)=ukTjiδjkei=ujTjiei(\mathbf{T}^\top \cdot \mathbf{u}) = u_k T_{ji} \delta_{jk} \mathbf{e}_i = u_j T_{ji} \mathbf{e}_i

Step 3: Subtract the Two Terms

The subtraction of the two terms is: (uT)(Tu)=(uiTijej)(ujTjiei)(\mathbf{u} \cdot \mathbf{T}) - (\mathbf{T}^\top \cdot \mathbf{u}) = (u_i T_{ij} \mathbf{e}_j) - (u_j T_{ji} \mathbf{e}_i)

Breaking this into components: (uTTu)=uiTijejujTjiei(\mathbf{u} \cdot \mathbf{T} - \mathbf{T}^\top \cdot \mathbf{u}) = u_i T_{ij} \mathbf{e}_j - u_j T_{ji} \mathbf{e}_i

Step 4: Component Interpretation

The result is a vector, where the jj-th component is given by: (uiTij)(ujTji)(u_i T_{ij}) - (u_j T_{ji})

This representation uses basis vectors (ei\mathbf{e}_i) and dyadics (eiej\mathbf{e}_i \otimes \mathbf{e}_j) to break the computation down into fundamental components.


Would you like further details on the steps or the interpretation of the result? Here are some related questions to explore further:

  1. How does the antisymmetric part of a tensor influence the result of this operation?
  2. How can we verify this computation in terms of physical or geometric properties?
  3. What happens if the tensor T\mathbf{T} is symmetric?
  4. How would this operation change in different coordinate systems?
  5. Can this expression be used to define a skew-symmetric tensor?

Tip: Pay close attention to the indices' arrangement when working with tensors; they directly control the transformation properties and the resulting operations.

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Math Problem Analysis

Mathematical Concepts

Linear Algebra
Tensor Analysis
Vector Calculus

Formulas

u · T = u_i T_{ij} e_j
T^T · u = u_j T_{ji} e_i
u · T - T^T · u = u_i T_{ij} e_j - u_j T_{ji} e_i

Theorems

Properties of Transpose of a Tensor
Dot Product of Basis Vectors
Tensor Representation in Basis Form

Suitable Grade Level

Undergraduate Level