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I redirected conservation of parity here because it is discussed in the article, but it would be good to increase its visibility. -- Kjkolb 07:35, 25 November 2005 (UTC)
How could it be, then if F=B+L, and if B=L=0 for Majorana neutrinos, then F=1 ?
Why Q (electric charge) is mentioned as a charge of a global symmetry group?
Hidaspal 21:13, 27 April 2006 (UTC)
"In a quantum theory states in a Hilbert space do not need to transform under representations of the group of rotations, but only under projective representations." - it sounds like a restriction though there is an extension in reality from representations of O(3) to SU(2). Projective to what? There are a lot of missing statements, which makes the whole thing unclear and ununderstandable. Hidaspal 21:30, 27 April 2006 (UTC)
It is written
"Quantum theory predicts that states in a Hilbert space do not need to transform under representations of the group of rotations, but only under projective representations. The word projective refers to the fact that if one projects out the phase of each state, where we recall that the overall phase of a quantum state is not observable, then a projective representation reduces to an ordinary representation. All representations are also projective representations, but the converse is not true, therefore the projective representation condition on quantum states is weaker than the representation condition on classical states."
But if representations form a strict subclass of projective representations, shouldn't the projective representation condition be a stronger one than the representation not make sense, and also, doesn't the "do not need...but only" construction in the first sentence not make sense? I think I am implicitly assuming that phrases like "transforms under representations of the group of rotations" mean "transforms under all such representations". I may be wrong about this, and, if so, would like to be corrected, but if some other interpretation is needed, perhaps the article should be rewritten to be made clearer. Nwalton125 ( talk) 19:33, 3 July 2022 (UTC)
The first line states "...a parity transformation is the simultaneous flip in the sign of all spatial coordinates." Almost directly below this it is stated that "In a two-dimensional plane, parity is not the same as a rotation by 180 degrees." These two statements blatantly contradict each other. Shambolic Entity 02:01, 25 January 2007 (UTC)
Well if you calculate the determinant for a 2d matrix with ((-1,0),(0,-1)) then you get +1 (rotation) which is consistent with the text I just quoted (both the ANY dimensions part, and the 2D example part). However it is still inconsistent with what everyone is talking about here: simply flipping the sign of all coordinates does not (always) work. And because we shouldn't expect the average reader to be able to calculate N-dimensional determinants in their head, this is just a mass of confusion.
I think the solution is to write early in the intro what another suggested before; that a parity transform occurs when you negate an odd number of elements, in any dimension; and perhaps point out that for 3 dimensions, this is the same as negating all coordinates. And perhaps also clarify (later in the intro, where my quote came from) that negating all coordinates in 2 dimensions is not parity change because it is not an odd number of elements being negated. But that seems it might be confusing too... I guess I would try editing the page right now, if I were an expert or had a reliable source... opinions ? Hydradix ( talk) 03:17, 2 August 2016 (UTC)
This article could really use a definition of instrinsic parity. I would do it myself but, since that is the topic I came here to learn about, I don't know the definition myself. Tpellman ( talk) 17:22, 29 April 2008 (UTC)
Although the neutral pion decay at the bottom of the article is indeed electromagnetic, and parity is conserved, the interaction still INVOLVES the weak interaction - the Standard Model plonks a virtual kaon in there, which of course arises from weak decay. Would it not be better to replace this with, e.g., rho decay to pions or something? Of course, there are always going to be virtual weak interactions integrated over for any process but with the neutral pion interaction it's actually always there. If no complaints, I'll change it. —Preceding unsigned comment added by 41.145.40.166 ( talk) 19:11, 1 October 2009 (UTC)
The article mentions that parity symmetry is 'maximally' violated by the weak force. Does the standard model lagrangian itself violate parity symmetry, or is it somehow due to the spontaneously broken symmetry that gives the vacuum a non-zero higgs expectation value?
Also, since CPT is (required?) a symmetry of particle physics, then parity symmetry violation implies time reversal symmetry violation in a very specific way. This seems weird to me. Can someone comment on this in the article? It seems very interesting.
Looking at the definition of an inertial frame in wikipedia, a parity transformation would yield another inertial coordinate system. Since SR requires physics to be the same in all inertial coordinate systems, yet experiments show there is not parity symmetry in weak decays, either the inertial frame article, or the special relativity article, or this article on parity needs to be updated. Otherwise wikipedia seems to imply that experiments on parity disprove special relativity.
130.126.14.198 ( talk) 08:11, 26 January 2010 (UTC)
An NYT article was published yesterday that discusses a brief parity violation observed at the Brookhaven collider. This should be added, and the article can be found here: http://www.nytimes.com/2010/02/16/science/16quark.html?th&emc=th 68.231.22.246 ( talk) 16:18, 16 February 2010 (UTC)
This is clearly one of a group of related articles including T-symmetry, C-symmetry and C-Parity. The naming as Parity is unhelpful, seeming to suggest that the other ideas are somehow subordinate to this idea. There is clearly some overriding idea to which these articles contribute, but it is not clear what this idea is. I would guess they all address some aspect of the question of invariance of the laws on physics under various transformations. As I am a novice trying to learn the subject, indication of this would help.
Turning to this particular article:
There is no explanation of why parity is relevant. Symmetry relations are the first topic after the introduction with no explanation as to why.
The statement “In physics parity relates to the sign of a spatial coordinate” can only apply to P-parity. It cannot apply to parity in physics in general.
The article does not define the values that parity can take, although by implication they seem to be +1 and -1. How to calculate parity in some particular circumstance is not defined. If I have an n-dimensional spatial vector containing both positive and negative terms, what is its parity? There is some discussion of the determinant of transformation matrices in 2 and 3 dimensions with value +1 and -1 relating to reflection and rotation. The article does not say whether the value of the determinant in some way defines parity.
Confusingly, having defined parity by ‘sign’, the section ‘Effect of spatial inversion on some variables of classical physics’ classifies variables according to odd and even parity (which is the mathematical concept of parity). The related T-symmetry and C-symmetry articles also refer to even/odd parity.
The article specifies an operation, ‘inversion’, as the ‘flip’ of the sign of a spatial coordinate. Is this formally the reflection in that axis? The other symmetry/parity articles variously use ‘conjugate’ and ‘reversal’ to describe the ‘flip of the sign’; this is unhelpful. Parity inversion is given the confusing synonym ‘parity transformation’ as if there was no other possible transformation of parity.
In example considering three dimensions:
might better be written as
Albear-And (
talk)
05:45, 17 February 2010 (UTC)
Wikipedia is a public use encyclopedia and wherever possible, should include descriptions understandable to the general public (non-scientist lay persons). Scientific language and formulas may be included, but should be in parallel to common-language explanations so that non-scientist readers can understand as much of Wikipedia as possible.
Remember that the main purpose of encyclopedia's in general (and Wikipedia in particular) is to educate and uplift the average reader-- not to to talk in a secretive code between members of a scientific "in-crowd". Science journals are for that, and also serve a valuable purpose, but encyclopedias have a different purpose.
Sean7phil ( talk) 17:17, 31 March 2010 (UTC)
There should be a section on parity in atomic and molecular optics. Parity provides one of the primary selection rules for determining optical transitions in atomic and simple molecular species. In the dipole approximation, transitions between different electronic states are mediated by the electric dipole operator, which has negative parity. Therefore non-vanishing transition amplitudes are only possible between states of opposite parity for single photon absorption, and between states of the same parity for two-photon absorption. As optical absorption spectroscopy can only detect transitions between states of opposite parity, other means are needed to complete the entire energy spectrum comprising states with the same parity as the ground state. —Preceding unsigned comment added by 130.102.172.3 ( talk) 01:48, 3 June 2010 (UTC)
"Then, combining them with rotations (or successively performing x-, y-, and z-reflections) one can recover the particular parity transformation defined earlier. The first parity transformation given does not work in an even number of dimensions, though, because it results in a positive determinant. In odd number of dimensions only the latter example of a parity transformation (or any reflection of an odd number of coordinates) can be used."
"..defined earlier." "The first parity transform..." "the latter example" These seem to be needed to be updated, since the first paragraph was changed. Unless I'm confused. Or just eliminate unneeded verbiage. GangofOne ( talk) 04:12, 18 July 2012 (UTC)
"and so we can choose to call P our parity operator instead of P." I leave for someone else to fix. GangofOne ( talk) 04:12, 18 July 2012 (UTC)
The article is on parity (in physics); the intro starts by defining what a parity transformation is.
Parity inversion may be important information within the topic, but it isn't the topic itself. Can someone ensure the intro explains its topic? FT2 ( Talk | email) 12:29, 11 March 2013 (UTC)
The article introduction begins by talking about a transformation which changes parity (determinant -1) or does not (in particular, rotation has determinant of +1). The next section (Simple symmetry relations) also uses similar equations/relations (like P=1 and P=-1)... but this is confusing in regards to the introduction...
Worse, the article then switches to discussing parity in terms of Even and Odd. There is no explanation how even and odd relate to +1 and -1. I'm guessing this has to do with the expression (-1)n ? Such that, if n is even then the result is +1 (no parity change / achiral), and if n is odd then the result is -1 (parity change / chiral). That's what I'm thinking, but don't have a source to confirm my theory. Does anybody know for sure? Hydradix ( talk) 06:29, 2 August 2016 (UTC)
Is this measurement notable to be mentioned in Parity (physics)#parity violation? -- HNAKXR ( talk) 08:28, 10 February 2014 (UTC)
I am removing my own sister link to a Wikiversity article that I wrote. For the record, the link was to Wikiversity:Special:Permalink/1571843, but the actual page is now blanked. I am beginning to realize that instead of proving that this was the proper state associated with two photon decay of even parity, I simply wrote it down. At issue is whether I prove uniqueness of the solution that I wrote down. I will eventually write something in that page, because I did prove that the entangled state does have the proper parity, but without a uniqueness proof it has little value.-- Guy vandegrift ( talk) 19:04, 24 May 2016 (UTC)
As per discussion at AfD. See Wikipedia:Articles for deletion/(−1)F for details ~ Amkgp 💬 19:59, 29 October 2020 (UTC)
![]() | This ![]() It is of interest to the following WikiProjects: | ||||||||||
|
![]() |
Daily pageviews of this article
A graph should have been displayed here but
graphs are temporarily disabled. Until they are enabled again, visit the interactive graph at
pageviews.wmcloud.org |
I redirected conservation of parity here because it is discussed in the article, but it would be good to increase its visibility. -- Kjkolb 07:35, 25 November 2005 (UTC)
How could it be, then if F=B+L, and if B=L=0 for Majorana neutrinos, then F=1 ?
Why Q (electric charge) is mentioned as a charge of a global symmetry group?
Hidaspal 21:13, 27 April 2006 (UTC)
"In a quantum theory states in a Hilbert space do not need to transform under representations of the group of rotations, but only under projective representations." - it sounds like a restriction though there is an extension in reality from representations of O(3) to SU(2). Projective to what? There are a lot of missing statements, which makes the whole thing unclear and ununderstandable. Hidaspal 21:30, 27 April 2006 (UTC)
It is written
"Quantum theory predicts that states in a Hilbert space do not need to transform under representations of the group of rotations, but only under projective representations. The word projective refers to the fact that if one projects out the phase of each state, where we recall that the overall phase of a quantum state is not observable, then a projective representation reduces to an ordinary representation. All representations are also projective representations, but the converse is not true, therefore the projective representation condition on quantum states is weaker than the representation condition on classical states."
But if representations form a strict subclass of projective representations, shouldn't the projective representation condition be a stronger one than the representation not make sense, and also, doesn't the "do not need...but only" construction in the first sentence not make sense? I think I am implicitly assuming that phrases like "transforms under representations of the group of rotations" mean "transforms under all such representations". I may be wrong about this, and, if so, would like to be corrected, but if some other interpretation is needed, perhaps the article should be rewritten to be made clearer. Nwalton125 ( talk) 19:33, 3 July 2022 (UTC)
The first line states "...a parity transformation is the simultaneous flip in the sign of all spatial coordinates." Almost directly below this it is stated that "In a two-dimensional plane, parity is not the same as a rotation by 180 degrees." These two statements blatantly contradict each other. Shambolic Entity 02:01, 25 January 2007 (UTC)
Well if you calculate the determinant for a 2d matrix with ((-1,0),(0,-1)) then you get +1 (rotation) which is consistent with the text I just quoted (both the ANY dimensions part, and the 2D example part). However it is still inconsistent with what everyone is talking about here: simply flipping the sign of all coordinates does not (always) work. And because we shouldn't expect the average reader to be able to calculate N-dimensional determinants in their head, this is just a mass of confusion.
I think the solution is to write early in the intro what another suggested before; that a parity transform occurs when you negate an odd number of elements, in any dimension; and perhaps point out that for 3 dimensions, this is the same as negating all coordinates. And perhaps also clarify (later in the intro, where my quote came from) that negating all coordinates in 2 dimensions is not parity change because it is not an odd number of elements being negated. But that seems it might be confusing too... I guess I would try editing the page right now, if I were an expert or had a reliable source... opinions ? Hydradix ( talk) 03:17, 2 August 2016 (UTC)
This article could really use a definition of instrinsic parity. I would do it myself but, since that is the topic I came here to learn about, I don't know the definition myself. Tpellman ( talk) 17:22, 29 April 2008 (UTC)
Although the neutral pion decay at the bottom of the article is indeed electromagnetic, and parity is conserved, the interaction still INVOLVES the weak interaction - the Standard Model plonks a virtual kaon in there, which of course arises from weak decay. Would it not be better to replace this with, e.g., rho decay to pions or something? Of course, there are always going to be virtual weak interactions integrated over for any process but with the neutral pion interaction it's actually always there. If no complaints, I'll change it. —Preceding unsigned comment added by 41.145.40.166 ( talk) 19:11, 1 October 2009 (UTC)
The article mentions that parity symmetry is 'maximally' violated by the weak force. Does the standard model lagrangian itself violate parity symmetry, or is it somehow due to the spontaneously broken symmetry that gives the vacuum a non-zero higgs expectation value?
Also, since CPT is (required?) a symmetry of particle physics, then parity symmetry violation implies time reversal symmetry violation in a very specific way. This seems weird to me. Can someone comment on this in the article? It seems very interesting.
Looking at the definition of an inertial frame in wikipedia, a parity transformation would yield another inertial coordinate system. Since SR requires physics to be the same in all inertial coordinate systems, yet experiments show there is not parity symmetry in weak decays, either the inertial frame article, or the special relativity article, or this article on parity needs to be updated. Otherwise wikipedia seems to imply that experiments on parity disprove special relativity.
130.126.14.198 ( talk) 08:11, 26 January 2010 (UTC)
An NYT article was published yesterday that discusses a brief parity violation observed at the Brookhaven collider. This should be added, and the article can be found here: http://www.nytimes.com/2010/02/16/science/16quark.html?th&emc=th 68.231.22.246 ( talk) 16:18, 16 February 2010 (UTC)
This is clearly one of a group of related articles including T-symmetry, C-symmetry and C-Parity. The naming as Parity is unhelpful, seeming to suggest that the other ideas are somehow subordinate to this idea. There is clearly some overriding idea to which these articles contribute, but it is not clear what this idea is. I would guess they all address some aspect of the question of invariance of the laws on physics under various transformations. As I am a novice trying to learn the subject, indication of this would help.
Turning to this particular article:
There is no explanation of why parity is relevant. Symmetry relations are the first topic after the introduction with no explanation as to why.
The statement “In physics parity relates to the sign of a spatial coordinate” can only apply to P-parity. It cannot apply to parity in physics in general.
The article does not define the values that parity can take, although by implication they seem to be +1 and -1. How to calculate parity in some particular circumstance is not defined. If I have an n-dimensional spatial vector containing both positive and negative terms, what is its parity? There is some discussion of the determinant of transformation matrices in 2 and 3 dimensions with value +1 and -1 relating to reflection and rotation. The article does not say whether the value of the determinant in some way defines parity.
Confusingly, having defined parity by ‘sign’, the section ‘Effect of spatial inversion on some variables of classical physics’ classifies variables according to odd and even parity (which is the mathematical concept of parity). The related T-symmetry and C-symmetry articles also refer to even/odd parity.
The article specifies an operation, ‘inversion’, as the ‘flip’ of the sign of a spatial coordinate. Is this formally the reflection in that axis? The other symmetry/parity articles variously use ‘conjugate’ and ‘reversal’ to describe the ‘flip of the sign’; this is unhelpful. Parity inversion is given the confusing synonym ‘parity transformation’ as if there was no other possible transformation of parity.
In example considering three dimensions:
might better be written as
Albear-And (
talk)
05:45, 17 February 2010 (UTC)
Wikipedia is a public use encyclopedia and wherever possible, should include descriptions understandable to the general public (non-scientist lay persons). Scientific language and formulas may be included, but should be in parallel to common-language explanations so that non-scientist readers can understand as much of Wikipedia as possible.
Remember that the main purpose of encyclopedia's in general (and Wikipedia in particular) is to educate and uplift the average reader-- not to to talk in a secretive code between members of a scientific "in-crowd". Science journals are for that, and also serve a valuable purpose, but encyclopedias have a different purpose.
Sean7phil ( talk) 17:17, 31 March 2010 (UTC)
There should be a section on parity in atomic and molecular optics. Parity provides one of the primary selection rules for determining optical transitions in atomic and simple molecular species. In the dipole approximation, transitions between different electronic states are mediated by the electric dipole operator, which has negative parity. Therefore non-vanishing transition amplitudes are only possible between states of opposite parity for single photon absorption, and between states of the same parity for two-photon absorption. As optical absorption spectroscopy can only detect transitions between states of opposite parity, other means are needed to complete the entire energy spectrum comprising states with the same parity as the ground state. —Preceding unsigned comment added by 130.102.172.3 ( talk) 01:48, 3 June 2010 (UTC)
"Then, combining them with rotations (or successively performing x-, y-, and z-reflections) one can recover the particular parity transformation defined earlier. The first parity transformation given does not work in an even number of dimensions, though, because it results in a positive determinant. In odd number of dimensions only the latter example of a parity transformation (or any reflection of an odd number of coordinates) can be used."
"..defined earlier." "The first parity transform..." "the latter example" These seem to be needed to be updated, since the first paragraph was changed. Unless I'm confused. Or just eliminate unneeded verbiage. GangofOne ( talk) 04:12, 18 July 2012 (UTC)
"and so we can choose to call P our parity operator instead of P." I leave for someone else to fix. GangofOne ( talk) 04:12, 18 July 2012 (UTC)
The article is on parity (in physics); the intro starts by defining what a parity transformation is.
Parity inversion may be important information within the topic, but it isn't the topic itself. Can someone ensure the intro explains its topic? FT2 ( Talk | email) 12:29, 11 March 2013 (UTC)
The article introduction begins by talking about a transformation which changes parity (determinant -1) or does not (in particular, rotation has determinant of +1). The next section (Simple symmetry relations) also uses similar equations/relations (like P=1 and P=-1)... but this is confusing in regards to the introduction...
Worse, the article then switches to discussing parity in terms of Even and Odd. There is no explanation how even and odd relate to +1 and -1. I'm guessing this has to do with the expression (-1)n ? Such that, if n is even then the result is +1 (no parity change / achiral), and if n is odd then the result is -1 (parity change / chiral). That's what I'm thinking, but don't have a source to confirm my theory. Does anybody know for sure? Hydradix ( talk) 06:29, 2 August 2016 (UTC)
Is this measurement notable to be mentioned in Parity (physics)#parity violation? -- HNAKXR ( talk) 08:28, 10 February 2014 (UTC)
I am removing my own sister link to a Wikiversity article that I wrote. For the record, the link was to Wikiversity:Special:Permalink/1571843, but the actual page is now blanked. I am beginning to realize that instead of proving that this was the proper state associated with two photon decay of even parity, I simply wrote it down. At issue is whether I prove uniqueness of the solution that I wrote down. I will eventually write something in that page, because I did prove that the entangled state does have the proper parity, but without a uniqueness proof it has little value.-- Guy vandegrift ( talk) 19:04, 24 May 2016 (UTC)
As per discussion at AfD. See Wikipedia:Articles for deletion/(−1)F for details ~ Amkgp 💬 19:59, 29 October 2020 (UTC)