How do I calculate 1-forms for a connection?

  • Thread starter Oxymoron
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In summary, in order to calculate the 1-forms using the given formula, a metric is needed. The metric given is for a 3-dimensional space of constant curvature c and an orthonormal frame is provided. Using this information, the formula is used to calculate the 1-forms, specifically the 1-form \omega_{12}. The 1-form is then simplified using substitutions and simplification rules.
  • #1
Oxymoron
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Why Cant I Calculate 1-forms!?

Ive been given the following formula to find 1-forms:

[tex]2\omega_{ab} = e^d i(X_a)i(X_b)\mbox{d}e_d + i(X_b)\mbox{d}e_a - i(X_a)\mbox{d}e_b[/tex]

and have been asked to find all connection 1-forms. Of course, you can't find these 1-forms without a metric, so here it is:

[tex]g = -\mbox{d}t\otimes\mbox{d}t + f(t)^2\hat{g}[/tex]

where [itex]\hat{g}[/itex] is the metric on some 3-dimensional space of constant curvature c. My orthonormal frame is

[tex]e^0 = \mbox{d}t \quad \quad e^i = f(t)\hat{e}^i[/tex]

where [itex]\hat{e}^i[/itex] is a [itex]\hat{g}[/itex]-orthonormal frame. And note that [itex]X_i = \frac{1}{f}\hat{X}_i[/itex]. Phew! Hope that's not too hard to comprehend.

But I don't know what to put in for d in the index of e. I am aware that you have to sum over d but I am not sure what to sum over. 0,1,2,3? EDIT: Yes, I sum over everything.
 
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  • #2
So here is how I attempted to calculate [itex]\omega_{12}[/itex]:

First I calculated that

[tex]\mbox{d}e^1 = f^{\prime}\mbox{d}t\wedge\hat{e}^1 + f\mbox{d}\hat{e}^1[/tex]
[tex]= \frac{f^{\prime}}{f}e^0\wedge e^1 + f\mbox{d}e^1[/tex]

and, similarly

[tex]\mbox{d}e^2 = \frac{f^{\prime}}{f}e^0\wedge e^2 + f\mbox{d}\hat{e}^2[/tex]

So then, using that equation and substituting d=0 (I don't even know if that's right), I get:

[tex]2\omega_{12} = e^di(X_1)i(X_2)\mbox{d}e_d + i(X_2)\mbox{d}e_1 - i(X_1)\mbox{d}e_2 [/tex]

[tex]= e^di(X_1)i(X_2)\mbox{d}e_d + i(X_2)\left[\frac{f^{\prime}}{f}e^0\wedge e^1 + f\mbox{d}\hat{e}^1\right] - i(X_1)\left[\frac{f^{\prime}}{f}e^0\wedge e^2 + f\mbox{d}\hat{e}^2\right] [/tex]

[tex]= e^di(X_1)i(X_2)\mbox{d}e_d + i(X_2)(f\mbox{d}\hat{e}^1) - i(X_1)(f\mbox{d}\hat{e}^2) + \frac{f^{\prime}}{f}\left[i(X_2)(e^0\wedge e^1) - i(X_1)(e^0 \wedge e^2)\right] [/tex]

[tex]= e^di(X_1)i(X_2)\mbox{d}e_d + \frac{1}{f}i(\hat{X}_2)(f\mbox{d}\hat{e}^1) - \frac{1}{f}i(\hat{X}_1)(f\mbox{d}\hat{e}^2) + \frac{f^{\prime}}{f}\left[i(X_2)(e^0\wedge e^1) - i(X_1)(e^0 \wedge e^2)\right] [/tex]

[tex]= \frac{1}{f^2}\hat{e}^di(\hat{X}_1)i(\hat{X}_2)\mbox{d}\hat{e}_d + i(\hat{X}_2)(\mbox{d}\hat{e}^1) - i(\hat{X}_1)(\mbox{d}\hat{e}^2) + \frac{f^{\prime}}{f}\left[i(X_2)(e^0\wedge e^1) - i(X_1)(e^0 \wedge e^2)\right] [/tex]

[tex]= \frac{2}{f^2}\hat{\omega}_{12} + \frac{f^{\prime}}{f}\left[i(X_2)(e^0\wedge e^1) - i(X_1)(e^0 \wedge e^2)\right]
[/tex]
 
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FAQ: How do I calculate 1-forms for a connection?

Why are 1-forms important in science?

1-forms are important in science because they are a mathematical tool used to describe physical quantities such as force, energy, and momentum. They allow us to describe and analyze physical systems in a precise and concise manner.

What makes calculating 1-forms challenging?

Calculating 1-forms can be challenging because it involves understanding and manipulating mathematical concepts such as vector calculus, differential forms, and exterior derivatives. It also requires a solid understanding of the underlying physical principles and equations.

Can you give an example of a real-world application of 1-forms?

One example of a real-world application of 1-forms is in fluid dynamics, where they are used to describe the flow of fluids in a precise and efficient manner. 1-forms can also be used in electromagnetism, where they help describe electric and magnetic fields.

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Understanding 1-forms can improve your scientific research by providing you with a powerful tool for analyzing and describing physical systems. It can also help you make connections between different areas of science and identify underlying patterns and principles.

What resources are available for learning about 1-forms?

There are several resources available for learning about 1-forms, including textbooks, online lectures and tutorials, and academic courses. It is also helpful to have a strong understanding of linear algebra, calculus, and physics before delving into 1-forms.

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