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Ask HN: Can you suggest advanced books on integral calculation?

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Re: Ask HN: Can you suggest advanced books on integral calculation?

#21
post #15
post #11

Along a similar line, the only book that I've found that has goes through a careful derivation of the divergence theorem using Lebesgue integration is, "A Concise Introduction to the Theory of Integration," Second Edition by Daniel W. Stroock. I prefer this one to his later book, "Essentials of Integration Theory for Analysis." Does anyone else have a good reference or book on the topic?

This is an amazing book and I'm so suprised to see someone else knows about it. However , who cares about the Lebesgue integral? The only thing its good for is integrating pathological functions like the rationals, the indicator of the Cantor set, and fractals. Riemann integration is just fine and I'm not sure what all the fuss is about the Lebesgue Integral. Sure expectation of a random variable is a Lebesgue integr…

Well the mathematicians care for those pathological cases. Probably the most important of said pathological cases is Brownian motion / Weiner processes / SDEs. Brownian motion is differential with zero probability, yet it has many modeling applications. It is also fractal-like (the self-similarity property).

The more practical advantage measure theory provides for probability is you can simultaneously handle continuous and discrete distributions. Most of the time what works for one works for the other but you can get some weird mistakes (Shannon’s differential entropy has a few issues as a measure of information not found in the discrete case because he got lazy and just replaced the sum with an integral).

A good chunk of the time I come across measure theoretic probability papers I feel like they’re making the paper a lot more complicated and messier than it needs to be, but it does serve a purpose.

Re: Ask HN: Can you suggest advanced books on integral calculation?

#23

As practical advice (not addressing your enjoyment), learn how to use a CAS effectively. That will have a ton more bang for the buck in studying physics than being able to occasionally impress yourself with a Feynman trick or obscure application of the King property.

what CAS do you recommend? Are the open source alternatives at the same level as licensed ones? I know Mathematica from Wolfram is well used in the territory. And how does one learn how to use those?

Re: Ask HN: Can you suggest advanced books on integral calculation?

#24
post #15
post #11

Along a similar line, the only book that I've found that has goes through a careful derivation of the divergence theorem using Lebesgue integration is, "A Concise Introduction to the Theory of Integration," Second Edition by Daniel W. Stroock. I prefer this one to his later book, "Essentials of Integration Theory for Analysis." Does anyone else have a good reference or book on the topic?

This is an amazing book and I'm so suprised to see someone else knows about it. However , who cares about the Lebesgue integral? The only thing its good for is integrating pathological functions like the rationals, the indicator of the Cantor set, and fractals. Riemann integration is just fine and I'm not sure what all the fuss is about the Lebesgue Integral. Sure expectation of a random variable is a Lebesgue integr…

As mentioned in a sibling comment, Lebesgue integration can be helpful with probability theory because we can wrap some information into the measure rather than the function. Though, to be sure, this can often be done in a similar manner using the Riemann-Stieltjes integral.

To me, part of the value of Lebesgue integration is in understanding the limitations of Riemann integrals and when they break. Some of this is covered in Stroock's book in chapter 5.1. Alternatively, when in working in function spaces, we may need to integrate in a more general way than Lebesgue integration, so things like Bochner integrals, which require similar theory. This can arise in the theory related to things like PDE constrained optimization, which most of the time is targeted toward physics related models.

All that said, bluntly, I prefer to work with Riemann integrals when at all possible. However, the same question then applies. Do you or someone else have a reference for a rigorous derivation of the divergence theorem or integration by parts in multiple dimensions using Riemann integration? It's not particularly hard in one dimension, but higher dimensions is tricky and it's hard to get the details of integrating on the surface correct. Stroock's book is the only reference that I know of and he does it with Lebesgue integration.

Re: Ask HN: Can you suggest advanced books on integral calculation?

#25
post #23

As practical advice (not addressing your enjoyment), learn how to use a CAS effectively. That will have a ton more bang for the buck in studying physics than being able to occasionally impress yourself with a Feynman trick or obscure application of the King property.

what CAS do you recommend? Are the open source alternatives at the same level as licensed ones? I know Mathematica from Wolfram is well used in the territory. And how does one learn how to use those?

I personally use Maxima and Sage. They're not as polished as Mathematica by a long shot, but they're free and very useful when it you get enough practice with them.

Re: Ask HN: Can you suggest advanced books on integral calculation?

#26
post #22

It might be a bit disappointing, but there aren’t much in the way of next level techniques. Sure there might be one off tricks to solve specific problems, but for integration these tend not to be useful in general.

> Sure there might be one off tricks to solve specific problems

There is a widely applicable generic algorithm for indefinite integration (https://en.wikipedia.org/wiki/Risch_algorithm).

> but for integration these tend not to be useful in general.

That is true. For many problems, simpler methods work.

Also, according to that page “Currently, there is no known full implementation of the Risch algorithm”.

Re: Ask HN: Can you suggest advanced books on integral calculation?

#27
post #21
post #15

Earlier quoted context omitted.

This is an amazing book and I'm so suprised to see someone else knows about it. However , who cares about the Lebesgue integral? The only thing its good for is integrating pathological functions like the rationals, the indicator of the Cantor set, and fractals. Riemann integration is just fine and I'm not sure what all the fuss is about the Lebesgue Integral. Sure expectation of a random variable is a Lebesgue integr…

Well the mathematicians care for those pathological cases. Probably the most important of said pathological cases is Brownian motion / Weiner processes / SDEs. Brownian motion is differential with zero probability, yet it has many modeling applications. It is also fractal-like (the self-similarity property). The more practical advantage measure theory provides for probability is you can simultaneously handle continuo…

[deleted]

Re: Ask HN: Can you suggest advanced books on integral calculation?

#28
post #15
post #11

Along a similar line, the only book that I've found that has goes through a careful derivation of the divergence theorem using Lebesgue integration is, "A Concise Introduction to the Theory of Integration," Second Edition by Daniel W. Stroock. I prefer this one to his later book, "Essentials of Integration Theory for Analysis." Does anyone else have a good reference or book on the topic?

This is an amazing book and I'm so suprised to see someone else knows about it. However , who cares about the Lebesgue integral? The only thing its good for is integrating pathological functions like the rationals, the indicator of the Cantor set, and fractals. Riemann integration is just fine and I'm not sure what all the fuss is about the Lebesgue Integral. Sure expectation of a random variable is a Lebesgue integr…

Interchange of limits and integrals is more straightforward with Lebesgue integrals.

Re: Ask HN: Can you suggest advanced books on integral calculation?

#29

Since you are already doing this, can you suggest some good books you have be using for beginners. ?

I really liked the calculus book by Swokowski. The books starts with a revision of the requirements to start learning derivatives, has sections dedicated to applications of that and then goes on to integrals, analytical geometry and differential equations. It will keep you entertained for months.

Re: Ask HN: Can you suggest advanced books on integral calculation?

#30
It's fantastic that you enjoy tackling challenging integrals, especially as you embark on your master's in physics! To master advanced techniques, consider exploring resources like "Advanced Calculus" by Patrick M. Fitzpatrick, or delving into specific areas like contour integration for complex analysis.
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