"Symmetry and conserved quantitiy : Noether's theorem"의 두 판 사이의 차이
둘러보기로 가기
검색하러 가기
Pythagoras0 (토론 | 기여) |
Pythagoras0 (토론 | 기여) |
||
| (같은 사용자의 중간 판 3개는 보이지 않습니다) | |||
| 6번째 줄: | 6번째 줄: | ||
* Noether's theorem : extreme+invariance -> conservation law | * Noether's theorem : extreme+invariance -> conservation law | ||
* {{수학노트|url=연속_방정식}} | * {{수학노트|url=연속_방정식}} | ||
| − | + | ||
| − | + | ||
==field theoretic formulation== | ==field theoretic formulation== | ||
| − | * <math>\alpha_{s}</math> continuous symmetry with parameter s, i.e. the action does not change by the action of | + | * <math>\alpha_{s}</math> continuous symmetry with parameter s, i.e. the action does not change by the action of <math>\alpha_{s}</math> |
| − | * define the | + | * define the current density <math>j(x)=(j^0(x),j^1(x),j^2(x),j^3(x))</math> by |
:<math>j^{\mu}(x)= \frac{\partial \mathcal{L}}{\partial ( \partial_\mu \phi )}\left(\frac{\partial\alpha_{s}(\phi)}{\partial s} \right) </math> | :<math>j^{\mu}(x)= \frac{\partial \mathcal{L}}{\partial ( \partial_\mu \phi )}\left(\frac{\partial\alpha_{s}(\phi)}{\partial s} \right) </math> | ||
* then it obeys the continuity equation | * then it obeys the continuity equation | ||
:<math>\partial_{\mu} j^{\mu}=\sum_{\mu=0}^{3}\frac{\partial j^{\mu}}{\partial x^{\mu}}=0</math> | :<math>\partial_{\mu} j^{\mu}=\sum_{\mu=0}^{3}\frac{\partial j^{\mu}}{\partial x^{\mu}}=0</math> | ||
* <math>j^{0}(x)</math> density of some abstract fluid | * <math>j^{0}(x)</math> density of some abstract fluid | ||
| − | * Put | + | * Put <math>\rho:=j_0</math> and <math>\mathbf{J}=(j_x,j_y,j_z)</math> velocity of this abstract fluid at each space time point |
* conserved charge | * conserved charge | ||
:<math>Q(t)=\int_V \rho \,d^3 x</math> | :<math>Q(t)=\int_V \rho \,d^3 x</math> | ||
:<math>\frac{dQ}{dt}=0</math> | :<math>\frac{dQ}{dt}=0</math> | ||
===gauge theory=== | ===gauge theory=== | ||
| − | * to each generator | + | * to each generator <math>T_a</math>, associate the current density |
:<math>j_{a}^{\mu}(x)= \frac{\partial \mathcal{L}}{\partial ( \partial_\mu \phi )}iT_a \phi</math> | :<math>j_{a}^{\mu}(x)= \frac{\partial \mathcal{L}}{\partial ( \partial_\mu \phi )}iT_a \phi</math> | ||
| 30번째 줄: | 30번째 줄: | ||
Equation (10.165) embodies the idea of local conservation, which is stronger than global conservation. Globally, something like energy could well be con-served in that it might disappear in one place only to reappear in another a long way away. But this seems never to be observed in Nature; if energy does disappear in one place and reappear in another, we always observe a current of energy in between those places. That is, energy is conserved locally, which is a much stronger idea than mere global conservation. Even so, it might well be that something can appear from nowhere in an apparent example of nonconser-vation. “Flatlanders” —beings who are confined to a 2-surface—might observe the arrival of a 2-sphere (i.e. a common garden-variety sphere that needs to be embedded in three dimensions) that passes through their world. What will they see? First, a dot appears, which rapidly grows into a circle before growing smaller again to eventually vanish. The Flatlanders have witnessed a higher-dimensional object passing through their world; they might well be perplexed, since the circle seemed to come out of the void before vanishing back into it. | Equation (10.165) embodies the idea of local conservation, which is stronger than global conservation. Globally, something like energy could well be con-served in that it might disappear in one place only to reappear in another a long way away. But this seems never to be observed in Nature; if energy does disappear in one place and reappear in another, we always observe a current of energy in between those places. That is, energy is conserved locally, which is a much stronger idea than mere global conservation. Even so, it might well be that something can appear from nowhere in an apparent example of nonconser-vation. “Flatlanders” —beings who are confined to a 2-surface—might observe the arrival of a 2-sphere (i.e. a common garden-variety sphere that needs to be embedded in three dimensions) that passes through their world. What will they see? First, a dot appears, which rapidly grows into a circle before growing smaller again to eventually vanish. The Flatlanders have witnessed a higher-dimensional object passing through their world; they might well be perplexed, since the circle seemed to come out of the void before vanishing back into it. | ||
| − | + | ||
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
==related items== | ==related items== | ||
| 45번째 줄: | 37번째 줄: | ||
* [[Emmy Noether’s Wonderful Theorem]] | * [[Emmy Noether’s Wonderful Theorem]] | ||
* [[Gauge theory]] | * [[Gauge theory]] | ||
| − | + | ||
| − | + | ||
==encyclopedia== | ==encyclopedia== | ||
| 55번째 줄: | 47번째 줄: | ||
==expositions== | ==expositions== | ||
| − | * [http://www.thetangentbundle.net/papers/gauge.pdf Connections, Gauges and Field Theories] | + | * [http://www.thetangentbundle.net/papers/gauge.pdf Connections, Gauges and Field Theories] |
| 66번째 줄: | 58번째 줄: | ||
[[분류:math and physics]] | [[분류:math and physics]] | ||
[[분류:classical mechanics]] | [[분류:classical mechanics]] | ||
| + | |||
| + | ==메타데이터== | ||
| + | ===위키데이터=== | ||
| + | * ID : [https://www.wikidata.org/wiki/Q578555 Q578555] | ||
| + | ===Spacy 패턴 목록=== | ||
| + | * [{'LOWER': 'noether'}, {'LOWER': "'s"}, {'LEMMA': 'theorem'}] | ||
| + | * [{'LOWER': 'noether'}, {'LOWER': "'s"}, {'LOWER': 'first'}, {'LEMMA': 'theorem'}] | ||
2021년 2월 17일 (수) 03:16 기준 최신판
introduction
- fields
- the condition for the extreme of a functional leads to Euler-Lagrange equation
- invariance of functional imposes another constraint
- Noether's theorem : extreme+invariance -> conservation law
- 틀:수학노트
field theoretic formulation
- \(\alpha_{s}\) continuous symmetry with parameter s, i.e. the action does not change by the action of \(\alpha_{s}\)
- define the current density \(j(x)=(j^0(x),j^1(x),j^2(x),j^3(x))\) by
\[j^{\mu}(x)= \frac{\partial \mathcal{L}}{\partial ( \partial_\mu \phi )}\left(\frac{\partial\alpha_{s}(\phi)}{\partial s} \right) \]
- then it obeys the continuity equation
\[\partial_{\mu} j^{\mu}=\sum_{\mu=0}^{3}\frac{\partial j^{\mu}}{\partial x^{\mu}}=0\]
- \(j^{0}(x)\) density of some abstract fluid
- Put \(\rho:=j_0\) and \(\mathbf{J}=(j_x,j_y,j_z)\) velocity of this abstract fluid at each space time point
- conserved charge
\[Q(t)=\int_V \rho \,d^3 x\] \[\frac{dQ}{dt}=0\]
gauge theory
- to each generator \(T_a\), associate the current density
\[j_{a}^{\mu}(x)= \frac{\partial \mathcal{L}}{\partial ( \partial_\mu \phi )}iT_a \phi\]
Local Versus Global Conservation
Equation (10.165) embodies the idea of local conservation, which is stronger than global conservation. Globally, something like energy could well be con-served in that it might disappear in one place only to reappear in another a long way away. But this seems never to be observed in Nature; if energy does disappear in one place and reappear in another, we always observe a current of energy in between those places. That is, energy is conserved locally, which is a much stronger idea than mere global conservation. Even so, it might well be that something can appear from nowhere in an apparent example of nonconser-vation. “Flatlanders” —beings who are confined to a 2-surface—might observe the arrival of a 2-sphere (i.e. a common garden-variety sphere that needs to be embedded in three dimensions) that passes through their world. What will they see? First, a dot appears, which rapidly grows into a circle before growing smaller again to eventually vanish. The Flatlanders have witnessed a higher-dimensional object passing through their world; they might well be perplexed, since the circle seemed to come out of the void before vanishing back into it.
encyclopedia
expositions
articles
- Herman, Jonathan. “Noether’s Theorem Under the Legendre Transform.” arXiv:1409.5837 [math-Ph], September 19, 2014. http://arxiv.org/abs/1409.5837.
메타데이터
위키데이터
- ID : Q578555
Spacy 패턴 목록
- [{'LOWER': 'noether'}, {'LOWER': "'s"}, {'LEMMA': 'theorem'}]
- [{'LOWER': 'noether'}, {'LOWER': "'s"}, {'LOWER': 'first'}, {'LEMMA': 'theorem'}]