Reindeer
Deinonychus
Joined: May 07, 2011
Age: 18
Posts: 372
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 Posted: Mon Mar 05, 2012 3:45 pm Post subject: |
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Well I LOVE physics and I am currently reading physics/mathematics at my college 
But I am better af physics than just pure mathematics >.>
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RoyK
Emu Egg
Joined: May 17, 2012
Age: 22
Posts: 3
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| Posted: Sat May 19, 2012 6:13 pm Post subject: |
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| Does anyone know how to find a zero of the Riemann zeta function? |
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ruveyn
Phoenix
Joined: Sep 22, 2008
Age: 76
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Location: New Jersey
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marshall
Under the whirlwind
Joined: Apr 15, 2007
Posts: 9192
Location: Western Michigan
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| Posted: Mon May 28, 2012 12:59 am Post subject: |
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| AspieRogue wrote: | | anxiouspoet wrote: | | marshall wrote: | | I guess despite the supposed stereotype there aren't a lot of aspies who love math. Right now I'm trying to self-teach myself axiomatic set theory. |
By "learning axiomatic set theory" do you mean learning ZFC (zermelo-fraenkel set theory with axiom of choice) and learning how to construct basic mathematical objects? That's fascinating stuff the first time you see it. It really helps build philosophical skill and faith in math to judge itself critically.
It can also be mind-bending to really examine those different levels of infinity. Not to mention when you get into constructability of universes, inner model theory, and forcing etc.etc. |
OF COURSE he means ZFC set theory! 
The other 3 set theories are based on ZFC+AC set theory so that is truly the foundation for axiomatic set theory. Model theory, which includes the study of constructable universes and Boolean algebras and introduces the forcing technique, is firmly rooted in first order logic. Most predicate logic classes are put under the philosophy department for some reason. |
I like the NBG formulation of set theory as it can be generated from a finite number of axioms while being logically identical to ZFC for statements not involving proper classes. |
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marshall
Under the whirlwind
Joined: Apr 15, 2007
Posts: 9192
Location: Western Michigan
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| Posted: Mon May 28, 2012 11:30 am Post subject: |
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| AspieRogue wrote: | | Model theory, which includes the study of constructable universes and Boolean algebras and introduces the forcing technique, is firmly rooted in first order logic. Most predicate logic classes are put under the philosophy department for some reason. |
I'd say Model theory is the application of algebraic and set-theoretic concepts to first-order logic itself. It's a weird concept to wrap my head around as my mind is trained to think in terms of logic without necessarily analyzing it from a mathematical point of view. |
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ruveyn
Phoenix
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Age: 76
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Location: New Jersey
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| Posted: Mon May 28, 2012 12:08 pm Post subject: |
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[quote="AspieRogue"
I tend to think of tensors as transformation matrices that allow you to determine the components of a vector in multiple coordinate systems. They make a lot of sense once you've studied matrix algebra and Vector spaces. Because a Tensor is a basically a cartesian product of vector spaces mapped into yet another vector space.
[/quote]
An F valued tensor is a multi-linear mapping from a cartesian product of vectors spaces and their dual spaces into the field F.
F could be the real numbers or F could be the complex numbers. The classical definition of tensors in terms of their components is an equivalence relation between components under a linear mapping.
ruveyn |
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ruveyn
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Joined: Sep 22, 2008
Age: 76
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Location: New Jersey
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| Posted: Mon May 28, 2012 2:24 pm Post subject: |
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| AspieRogue wrote: | | ruveyn wrote: | | AspieRogue wrote: |
I tend to think of tensors as transformation matrices that allow you to determine the components of a vector in multiple coordinate systems. They make a lot of sense once you've studied matrix algebra and Vector spaces. Because a Tensor is a basically a cartesian product of vector spaces mapped into yet another vector space.
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An F valued tensor is a multi-linear mapping from a cartesian product of vectors spaces and their dual spaces into the field F.
F could be the real numbers or F could be the complex numbers. The classical definition of tensors in terms of their components is an equivalence relation between components under a linear mapping.
ruveyn |
How does what I posted about tensors conflict with the definition you presented? Short answer: It doesn't. |
You said a tensor is a cartesian product. Nay, nay. It is a function. The cartesian product is the domain of the function. You also forgot to mention the dual vector spaces.
ruveyn |
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marshall
Under the whirlwind
Joined: Apr 15, 2007
Posts: 9192
Location: Western Michigan
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| Posted: Wed May 30, 2012 1:49 pm Post subject: |
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| AspieRogue wrote: | | ruveyn wrote: | | AspieRogue wrote: | | ruveyn wrote: | | AspieRogue wrote: |
I tend to think of tensors as transformation matrices that allow you to determine the components of a vector in multiple coordinate systems. They make a lot of sense once you've studied matrix algebra and Vector spaces. Because a Tensor is a basically a cartesian product of vector spaces mapped into yet another vector space.
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An F valued tensor is a multi-linear mapping from a cartesian product of vectors spaces and their dual spaces into the field F.
F could be the real numbers or F could be the complex numbers. The classical definition of tensors in terms of their components is an equivalence relation between components under a linear mapping.
ruveyn |
How does what I posted about tensors conflict with the definition you presented? Short answer: It doesn't. |
You said a tensor is a cartesian product. Nay, nay. It is a function. The cartesian product is the domain of the function. You also forgot to mention the dual vector spaces.
ruveyn |
It is both. I was talking about the Tensor Product. |
I'm trying to understand the connection between the mathematical definition of tensor and the definition physicists and fluid dynamicists use. I don't think I'm quite there yet. I usually prefer the definitions mathematicians devise in terms of precision and clarity, but they can be lacking in intuitive motivation.
In physics tensors are linear relations between vector quantities that preserve their geometric meaning under different choices of coordinate bases. Physical vectors have the same meaning as first order tensors and higher order tensors are linear geometrically preserving relations between two lower order tensors. My problem is the notation physicists use leads one to confuse the multi-dimensional arrays of numbers that represent tensors with tensors themselves. Tensors are really something more than just indexed multi-dimensional arrays. |
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Declension
Phoenix
Joined: Jan 21, 2012
Posts: 1653
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| Posted: Fri Jun 01, 2012 5:50 pm Post subject: |
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| modustollens wrote: | | I am not as advanced as set theory yet. |
Congratulations! In nine words, you have just revealed why reductionist theories of mathematics are silly. Although they can be satisfying when you are feeling obsessive.
I'm doing a Master's in mathematics; my topic is do with topology. I like topology because when I'm with topologists I can often just draw a picture to convince people of something, instead of having to jump through formal hoops. The formal hoops are important, of course, because they allow us to have a shared background theory within which we can interpret the pictures correctly. |
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marshall
Under the whirlwind
Joined: Apr 15, 2007
Posts: 9192
Location: Western Michigan
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| Posted: Fri Jun 01, 2012 9:32 pm Post subject: |
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| AspieRogue wrote: | | marshall wrote: |
I'm trying to understand the connection between the mathematical definition of tensor and the definition physicists and fluid dynamicists use. I don't think I'm quite there yet. I usually prefer the definitions mathematicians devise in terms of precision and clarity, but they can be lacking in intuitive motivation.
In physics tensors are linear relations between vector quantities that preserve their geometric meaning under different choices of coordinate bases. Physical vectors have the same meaning as first order tensors and higher order tensors are linear geometrically preserving relations between two lower order tensors. My problem is the notation physicists use leads one to confuse the multi-dimensional arrays of numbers that represent tensors with tensors themselves. Tensors are really something more than just indexed multi-dimensional arrays. |
You know about linear transformations, right? A linear transformation can qualify as a rank-2 tensor provided that it obeys the requisite transformation rules. Physicists generally work with tensors of rank 2. Tensors of higher rank are generally encountered more frequently in (pure)differential geometry and general relativity. |
I guess I'd like to understand precisely how the definition Ruveyn gave is equivalent to the definition used for continuum/fluid mechanics. I'm not sure how stress tensor and strain tensor are linear transformations |
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