What is the intuition behind quantization?
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It has long irked me that quantum mechanics appears to be so bound up in mysticism, if that isn't too strong a word.
It shouldn't be like that: it should be possible to follow the reasoning all the way back to some intuitively obvious axioms - "intuitively obvious" , at least if you invest enough in understanding the mathematics.
The way I was introduced to quantum mechanics years ago, it went something like: "First, you calculate the Hamiltonian, then mumble mumble and then you have the Hamiltonian Operator". I have never come across a good, intuitive explanation for why we should expect the apparently magical process of translating the classical Hamiltonian to an operator on (a dense subset of) a Hilbert space, $L^2(R^d)$, to work.
Where did the idea come from, that the physical state of a system should be described by a complex-valued "wave-function" and the observables are differential operators that act on wave-functions - and what was the intuitive reasoning behind? What is the mathematical justification - other than "it seems to work"?
The maths don't scare me - I have some understanding of manifolds, bundles, Lie algebras and -groups, I understand that wave-functions are sections of the base manifold into the complex line bundle and that you can, locally, consider them simply to be complex valued functions.
quantum-mechanics
add a comment |
up vote
3
down vote
favorite
It has long irked me that quantum mechanics appears to be so bound up in mysticism, if that isn't too strong a word.
It shouldn't be like that: it should be possible to follow the reasoning all the way back to some intuitively obvious axioms - "intuitively obvious" , at least if you invest enough in understanding the mathematics.
The way I was introduced to quantum mechanics years ago, it went something like: "First, you calculate the Hamiltonian, then mumble mumble and then you have the Hamiltonian Operator". I have never come across a good, intuitive explanation for why we should expect the apparently magical process of translating the classical Hamiltonian to an operator on (a dense subset of) a Hilbert space, $L^2(R^d)$, to work.
Where did the idea come from, that the physical state of a system should be described by a complex-valued "wave-function" and the observables are differential operators that act on wave-functions - and what was the intuitive reasoning behind? What is the mathematical justification - other than "it seems to work"?
The maths don't scare me - I have some understanding of manifolds, bundles, Lie algebras and -groups, I understand that wave-functions are sections of the base manifold into the complex line bundle and that you can, locally, consider them simply to be complex valued functions.
quantum-mechanics
2
I don't think that anyone, neither physicist nor mathematician, really knows why quantization works. As I've understood it, quantization isn't even well-defined; there might be several ways to quantize a given classical Lagrangian, but not all ways work.
– md2perpe
Jul 3 '17 at 15:32
add a comment |
up vote
3
down vote
favorite
up vote
3
down vote
favorite
It has long irked me that quantum mechanics appears to be so bound up in mysticism, if that isn't too strong a word.
It shouldn't be like that: it should be possible to follow the reasoning all the way back to some intuitively obvious axioms - "intuitively obvious" , at least if you invest enough in understanding the mathematics.
The way I was introduced to quantum mechanics years ago, it went something like: "First, you calculate the Hamiltonian, then mumble mumble and then you have the Hamiltonian Operator". I have never come across a good, intuitive explanation for why we should expect the apparently magical process of translating the classical Hamiltonian to an operator on (a dense subset of) a Hilbert space, $L^2(R^d)$, to work.
Where did the idea come from, that the physical state of a system should be described by a complex-valued "wave-function" and the observables are differential operators that act on wave-functions - and what was the intuitive reasoning behind? What is the mathematical justification - other than "it seems to work"?
The maths don't scare me - I have some understanding of manifolds, bundles, Lie algebras and -groups, I understand that wave-functions are sections of the base manifold into the complex line bundle and that you can, locally, consider them simply to be complex valued functions.
quantum-mechanics
It has long irked me that quantum mechanics appears to be so bound up in mysticism, if that isn't too strong a word.
It shouldn't be like that: it should be possible to follow the reasoning all the way back to some intuitively obvious axioms - "intuitively obvious" , at least if you invest enough in understanding the mathematics.
The way I was introduced to quantum mechanics years ago, it went something like: "First, you calculate the Hamiltonian, then mumble mumble and then you have the Hamiltonian Operator". I have never come across a good, intuitive explanation for why we should expect the apparently magical process of translating the classical Hamiltonian to an operator on (a dense subset of) a Hilbert space, $L^2(R^d)$, to work.
Where did the idea come from, that the physical state of a system should be described by a complex-valued "wave-function" and the observables are differential operators that act on wave-functions - and what was the intuitive reasoning behind? What is the mathematical justification - other than "it seems to work"?
The maths don't scare me - I have some understanding of manifolds, bundles, Lie algebras and -groups, I understand that wave-functions are sections of the base manifold into the complex line bundle and that you can, locally, consider them simply to be complex valued functions.
quantum-mechanics
quantum-mechanics
edited Nov 23 at 17:55
Cosmas Zachos
1,447520
1,447520
asked Jul 3 '17 at 13:22
j4nd3r53n
479310
479310
2
I don't think that anyone, neither physicist nor mathematician, really knows why quantization works. As I've understood it, quantization isn't even well-defined; there might be several ways to quantize a given classical Lagrangian, but not all ways work.
– md2perpe
Jul 3 '17 at 15:32
add a comment |
2
I don't think that anyone, neither physicist nor mathematician, really knows why quantization works. As I've understood it, quantization isn't even well-defined; there might be several ways to quantize a given classical Lagrangian, but not all ways work.
– md2perpe
Jul 3 '17 at 15:32
2
2
I don't think that anyone, neither physicist nor mathematician, really knows why quantization works. As I've understood it, quantization isn't even well-defined; there might be several ways to quantize a given classical Lagrangian, but not all ways work.
– md2perpe
Jul 3 '17 at 15:32
I don't think that anyone, neither physicist nor mathematician, really knows why quantization works. As I've understood it, quantization isn't even well-defined; there might be several ways to quantize a given classical Lagrangian, but not all ways work.
– md2perpe
Jul 3 '17 at 15:32
add a comment |
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You might enjoy Todorov's 2012 classic. As his Nelson quip summarizes, it is not a functor. Given a classical hamiltonian phase-space function, there are several "prescriptions" or "recipes" that yield the same operator-on-Hilbert-space answer. But, of course, there are counterexamples, which are a source of an almost century-old fascination. There is no "should". By ingenuity, luck, and trial-and-error, superheroes in the 1920s stumbled on it, and were pleased to note nature listened.
The cited article reminds you why, for flat geometry phase spaces the answers agree. Half of your problem is cultural: you are asked to compare and contrast theories defined in phase space and Hilbert space, respectively. There is a wonderful (but computationally demanding/barely-tractable) formulation of quantum mechanics in phase space which eliminates the culture problem and permits comparison and contrast of apples with apples. (But it assumes you are familiar with concepts of the Hilbert space/oranges formulation, really... Take a look at this introduction.)
The engine of this purely formal map from Hilbert space to phase space is the Wigner map, with an inverse given by the Weyl map.
Using the Weyl map, you may go from a classical hamiltonian to a unique quantum one, but, contrary to Weyl's 1927 wild guess, it is not superior, except computationally. By trial and error, people have discovered systems whose hamiltonian is not the Weyl image of a classical hamiltonian, and, in fact, physical systems with different hamiltonians, whose Wigner maps all have the same $hbarto 0$ classical hamiltonian limit.
So, as Todorov quips: "Quantization is a mystery".
Hi Cosmas - this is something like what I was hoping for. I will inspect the links and probably accept your answer after that. I really want to feel that I "understand" quantisation - you say that there is no "should", but I think there should be ;-) I believe that it is only by understanding quantisation, that we can repair whatever is broken between QM and GR. A question that is probably related: what happens to quantisation if space-time is far from being flat?
– j4nd3r53n
Nov 25 at 10:15
Indeed, quantization in curved spaces is an active area of research... a mystery....
– Cosmas Zachos
Nov 25 at 11:35
add a comment |
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You might enjoy Todorov's 2012 classic. As his Nelson quip summarizes, it is not a functor. Given a classical hamiltonian phase-space function, there are several "prescriptions" or "recipes" that yield the same operator-on-Hilbert-space answer. But, of course, there are counterexamples, which are a source of an almost century-old fascination. There is no "should". By ingenuity, luck, and trial-and-error, superheroes in the 1920s stumbled on it, and were pleased to note nature listened.
The cited article reminds you why, for flat geometry phase spaces the answers agree. Half of your problem is cultural: you are asked to compare and contrast theories defined in phase space and Hilbert space, respectively. There is a wonderful (but computationally demanding/barely-tractable) formulation of quantum mechanics in phase space which eliminates the culture problem and permits comparison and contrast of apples with apples. (But it assumes you are familiar with concepts of the Hilbert space/oranges formulation, really... Take a look at this introduction.)
The engine of this purely formal map from Hilbert space to phase space is the Wigner map, with an inverse given by the Weyl map.
Using the Weyl map, you may go from a classical hamiltonian to a unique quantum one, but, contrary to Weyl's 1927 wild guess, it is not superior, except computationally. By trial and error, people have discovered systems whose hamiltonian is not the Weyl image of a classical hamiltonian, and, in fact, physical systems with different hamiltonians, whose Wigner maps all have the same $hbarto 0$ classical hamiltonian limit.
So, as Todorov quips: "Quantization is a mystery".
Hi Cosmas - this is something like what I was hoping for. I will inspect the links and probably accept your answer after that. I really want to feel that I "understand" quantisation - you say that there is no "should", but I think there should be ;-) I believe that it is only by understanding quantisation, that we can repair whatever is broken between QM and GR. A question that is probably related: what happens to quantisation if space-time is far from being flat?
– j4nd3r53n
Nov 25 at 10:15
Indeed, quantization in curved spaces is an active area of research... a mystery....
– Cosmas Zachos
Nov 25 at 11:35
add a comment |
up vote
2
down vote
You might enjoy Todorov's 2012 classic. As his Nelson quip summarizes, it is not a functor. Given a classical hamiltonian phase-space function, there are several "prescriptions" or "recipes" that yield the same operator-on-Hilbert-space answer. But, of course, there are counterexamples, which are a source of an almost century-old fascination. There is no "should". By ingenuity, luck, and trial-and-error, superheroes in the 1920s stumbled on it, and were pleased to note nature listened.
The cited article reminds you why, for flat geometry phase spaces the answers agree. Half of your problem is cultural: you are asked to compare and contrast theories defined in phase space and Hilbert space, respectively. There is a wonderful (but computationally demanding/barely-tractable) formulation of quantum mechanics in phase space which eliminates the culture problem and permits comparison and contrast of apples with apples. (But it assumes you are familiar with concepts of the Hilbert space/oranges formulation, really... Take a look at this introduction.)
The engine of this purely formal map from Hilbert space to phase space is the Wigner map, with an inverse given by the Weyl map.
Using the Weyl map, you may go from a classical hamiltonian to a unique quantum one, but, contrary to Weyl's 1927 wild guess, it is not superior, except computationally. By trial and error, people have discovered systems whose hamiltonian is not the Weyl image of a classical hamiltonian, and, in fact, physical systems with different hamiltonians, whose Wigner maps all have the same $hbarto 0$ classical hamiltonian limit.
So, as Todorov quips: "Quantization is a mystery".
Hi Cosmas - this is something like what I was hoping for. I will inspect the links and probably accept your answer after that. I really want to feel that I "understand" quantisation - you say that there is no "should", but I think there should be ;-) I believe that it is only by understanding quantisation, that we can repair whatever is broken between QM and GR. A question that is probably related: what happens to quantisation if space-time is far from being flat?
– j4nd3r53n
Nov 25 at 10:15
Indeed, quantization in curved spaces is an active area of research... a mystery....
– Cosmas Zachos
Nov 25 at 11:35
add a comment |
up vote
2
down vote
up vote
2
down vote
You might enjoy Todorov's 2012 classic. As his Nelson quip summarizes, it is not a functor. Given a classical hamiltonian phase-space function, there are several "prescriptions" or "recipes" that yield the same operator-on-Hilbert-space answer. But, of course, there are counterexamples, which are a source of an almost century-old fascination. There is no "should". By ingenuity, luck, and trial-and-error, superheroes in the 1920s stumbled on it, and were pleased to note nature listened.
The cited article reminds you why, for flat geometry phase spaces the answers agree. Half of your problem is cultural: you are asked to compare and contrast theories defined in phase space and Hilbert space, respectively. There is a wonderful (but computationally demanding/barely-tractable) formulation of quantum mechanics in phase space which eliminates the culture problem and permits comparison and contrast of apples with apples. (But it assumes you are familiar with concepts of the Hilbert space/oranges formulation, really... Take a look at this introduction.)
The engine of this purely formal map from Hilbert space to phase space is the Wigner map, with an inverse given by the Weyl map.
Using the Weyl map, you may go from a classical hamiltonian to a unique quantum one, but, contrary to Weyl's 1927 wild guess, it is not superior, except computationally. By trial and error, people have discovered systems whose hamiltonian is not the Weyl image of a classical hamiltonian, and, in fact, physical systems with different hamiltonians, whose Wigner maps all have the same $hbarto 0$ classical hamiltonian limit.
So, as Todorov quips: "Quantization is a mystery".
You might enjoy Todorov's 2012 classic. As his Nelson quip summarizes, it is not a functor. Given a classical hamiltonian phase-space function, there are several "prescriptions" or "recipes" that yield the same operator-on-Hilbert-space answer. But, of course, there are counterexamples, which are a source of an almost century-old fascination. There is no "should". By ingenuity, luck, and trial-and-error, superheroes in the 1920s stumbled on it, and were pleased to note nature listened.
The cited article reminds you why, for flat geometry phase spaces the answers agree. Half of your problem is cultural: you are asked to compare and contrast theories defined in phase space and Hilbert space, respectively. There is a wonderful (but computationally demanding/barely-tractable) formulation of quantum mechanics in phase space which eliminates the culture problem and permits comparison and contrast of apples with apples. (But it assumes you are familiar with concepts of the Hilbert space/oranges formulation, really... Take a look at this introduction.)
The engine of this purely formal map from Hilbert space to phase space is the Wigner map, with an inverse given by the Weyl map.
Using the Weyl map, you may go from a classical hamiltonian to a unique quantum one, but, contrary to Weyl's 1927 wild guess, it is not superior, except computationally. By trial and error, people have discovered systems whose hamiltonian is not the Weyl image of a classical hamiltonian, and, in fact, physical systems with different hamiltonians, whose Wigner maps all have the same $hbarto 0$ classical hamiltonian limit.
So, as Todorov quips: "Quantization is a mystery".
edited Nov 23 at 17:42
answered Nov 23 at 17:29
Cosmas Zachos
1,447520
1,447520
Hi Cosmas - this is something like what I was hoping for. I will inspect the links and probably accept your answer after that. I really want to feel that I "understand" quantisation - you say that there is no "should", but I think there should be ;-) I believe that it is only by understanding quantisation, that we can repair whatever is broken between QM and GR. A question that is probably related: what happens to quantisation if space-time is far from being flat?
– j4nd3r53n
Nov 25 at 10:15
Indeed, quantization in curved spaces is an active area of research... a mystery....
– Cosmas Zachos
Nov 25 at 11:35
add a comment |
Hi Cosmas - this is something like what I was hoping for. I will inspect the links and probably accept your answer after that. I really want to feel that I "understand" quantisation - you say that there is no "should", but I think there should be ;-) I believe that it is only by understanding quantisation, that we can repair whatever is broken between QM and GR. A question that is probably related: what happens to quantisation if space-time is far from being flat?
– j4nd3r53n
Nov 25 at 10:15
Indeed, quantization in curved spaces is an active area of research... a mystery....
– Cosmas Zachos
Nov 25 at 11:35
Hi Cosmas - this is something like what I was hoping for. I will inspect the links and probably accept your answer after that. I really want to feel that I "understand" quantisation - you say that there is no "should", but I think there should be ;-) I believe that it is only by understanding quantisation, that we can repair whatever is broken between QM and GR. A question that is probably related: what happens to quantisation if space-time is far from being flat?
– j4nd3r53n
Nov 25 at 10:15
Hi Cosmas - this is something like what I was hoping for. I will inspect the links and probably accept your answer after that. I really want to feel that I "understand" quantisation - you say that there is no "should", but I think there should be ;-) I believe that it is only by understanding quantisation, that we can repair whatever is broken between QM and GR. A question that is probably related: what happens to quantisation if space-time is far from being flat?
– j4nd3r53n
Nov 25 at 10:15
Indeed, quantization in curved spaces is an active area of research... a mystery....
– Cosmas Zachos
Nov 25 at 11:35
Indeed, quantization in curved spaces is an active area of research... a mystery....
– Cosmas Zachos
Nov 25 at 11:35
add a comment |
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I don't think that anyone, neither physicist nor mathematician, really knows why quantization works. As I've understood it, quantization isn't even well-defined; there might be several ways to quantize a given classical Lagrangian, but not all ways work.
– md2perpe
Jul 3 '17 at 15:32