# Christoffel symbol and Einstein summation convention

• I
• Mathematicsresear
In summary, the conversation discusses the Christoffel symbols and their representation in terms of basis vectors and coordinate components. It is suggested to write the symbols in a certain form, but it is noted that this would not uniquely identify all of the symbols and only represents a subset of them. It is also mentioned that xk is not a component of a basis vector, but rather a coordinate.
Mathematicsresear

## Homework Statement

I know that by definition Γijkei=∂ej/∂xk implies that Γmjk=em ⋅ ∂ej/∂xk (e are basis vectors, xk is component of basis vector). Can I write it in the following form? Γjjk=ej ⋅ ∂ej/∂xk Why or why not?

## The Attempt at a Solution

While what you wrote would be valid, it would not uniquely identify the Christoffel symbols (it completely ignores the symbols ##\Gamma^i_{jk}## for which ##i \neq j## and sums over those where ##j = i##. Your equation has one free index and therefore represents n equations in an n-dimensional space. However, there are ##n^3## connection coefficients (##n^2(n+1)/2## if you require your connection to be torsion free).

Mathematicsresear said:
xk is component of basis vector
No it is not, it is a coordinate.

## 1. What is the Christoffel symbol?

The Christoffel symbol, also known as the Christoffel connection or Levi-Civita connection, is a set of coefficients that describe the connection between the tangent spaces of a smooth manifold. It is used in differential geometry to study the geometry of curved surfaces and higher-dimensional manifolds.

## 2. What is the Einstein summation convention?

The Einstein summation convention is a notation used in mathematics and physics to simplify expressions involving repeated indices. It states that when an index appears twice in a term, it is implicitly summed over all possible values. This convention is often used in conjunction with the Christoffel symbol in calculations involving tensors.

## 3. How are the Christoffel symbols related to the metric tensor?

The Christoffel symbols are related to the metric tensor through the geodesic equation, which describes the shortest path between two points on a curved surface. The Christoffel symbols are also used to define the covariant derivative, which measures the rate of change of a vector along a curve on the manifold.

## 4. What is the significance of the Christoffel symbols in general relativity?

In general relativity, the Christoffel symbols play a crucial role in the equations governing the behavior of matter and energy in the presence of strong gravitational fields. They are used to calculate the curvature of spacetime, which is responsible for the effects of gravity.

## 5. How do the Christoffel symbols and Einstein summation convention relate to each other?

The Christoffel symbols and Einstein summation convention are closely related because they both involve index notation. The Einstein summation convention is often used in calculations involving the Christoffel symbols and other tensors, making it a useful shorthand notation for complex equations in general relativity and differential geometry.

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