Assume that there exist anti-neutron stars in our galaxis. Would it be possible to distinguish a neutron star from an anti-neutron star just by means of astronomic observation data?
I think we have no sure theory to claim that we can determine which is matter and which is antimatter just by means of astronomic observation data. Of course if there is annihilation process just in progress, we can get some clues about antimatter in emission spectrum...
It should additionally be mentioned that my question is related to the question of what kind of particles are contained in stable nuclei, i.e. (protons)+(neutrons) or (protons)+(anti-neutrons) or (protons)+(neutrons)+(anti-neutrons).
The particle model I'm working on (preliminary research notes see http://kreuzer-dsr.de/kdsr/bulletin/KDSR_HypotronTheory_Flyer.pdf and http://kreuzer-dsr.de/kdsr/test/KDSR-PRS-02/KIPS/START-AND-RUN.htm) considers each (massive or massless) 'elementary particle' as a 'bound state' of 2x3=6 so-called 'hypotrons'. The up-quark and the down-quark are considered as 'bound states' of two hypotrons. Thereby (and finally), the neutron can be considered as a 'bound state' of (proton)+(electron)+(anti-neutrino), and the anti-neutron can be considered as a 'bound state' of (anti-proton)+(positron)+(neutrino). By means of a minimum principle concerning a (non-additive) quantity, which I called 'supercharge' and which is related to the charge of the hypotrons in a non-linear manner, it is possible to reproduce the 'valley of stable nuclei' provided that it is assumed that anti-neutrons are contained in nuclei instead of neutrons.
The fact that a decaying nucleus ejects a neutron might be considered as a result of a reaction (anti-neutron)+(neutrino)-->(neutron)+(anti-neutrino) INSIDE the nucleus which occurs randomly and which is considered to cause the decay.
Whether or not a particle and anti-particle annihilate under all (spatial) circumstances should be considered as an OPEN question. What can be observed in collision experiments (proton)->
The two answers on annihilation radiation depend on some subtle assumptions about the continuity of the intergalactic gas cloud being matter, which are further discussed at the link below.
With regard to why there is not an equality of antimatter, there are of course known cases of CP violation among mesons, but that only suggests we might find a similar violation among leptons or quarks, and we have not to my knowledge. There are also still some crazy ideas left over from the 1940s about antimatter being gravitationally repulsive, but this cannot be since its energy is positive.
The point Kruezer raises about the conditions of annihilation being experimentally limited to direct impact is interesting, but (a) how does this help? and (b) since antiparticles are attractive if they have any charge, direct collisions should be common.
I'm surprised someone hasn't proposed the old standby "symmetry breaking" for this one. I realize Dirac's original "electron sea" is not taken literally anymore, but assume it for the moment and consider if at high temperatures the electron sea was functionally a condensate?
You can take something out of a condensate or put something in without changing its state. If antiparticles are holes in the sea, then at high temperature when it was functioning as a condensate, you could create normal particles effectively without creating antiparticles. Technically you would have created one, but the condensate property would immediately render it unobservable.
Once the "sea" cools a bit, perhaps the holes remain, and you have antiparticles. By 10^-6 seconds most of the quarks and leptons are created, and it's still 10 quadrillion degrees. Turn off the condensate at that point, and voila, no antimatter in the universe.
http://www.scientificamerican.com/article/how-do-we-know-that-dista/
My study on quantum gravity and on combinations of GR with QM/QFT reveals the possibility that in large scales there could be graded shades of handedness and hence the degrees of variation how normal or anti- the matter is!
The annihilation energy of quick huge processes is maybe much less than multiple of 511 keV - low to radio waves perhaps. That can be the explanation why the annihilation marks has not yet been widely recognized, of course we need still better observation tools too...
Yes, one can distinguish observationally whether a pulsar is made of neutrons or anti-neutrons. The outer crust of an anti-neutron star would be made of anti-iron. Hence, any normal gas or cosmic rays (protons and heavy element nuclei) that fall on the anti-neutron star would result in emission of high energy gamma rays due to matter-anti matter annihilation bearing characteristic signatures.
Patrick,
How can you determine if it's anti-neutron star or normal neutron star when assuming there is the same amount of both in the universe on average?
Patrick,
Your conclusion relies on two assumptions: (1) nuclei contain neutrons and (2) particles and anti-particles annihilate under all circumstances.
In the particle model I mentioned above ( preliminary research notes see http://kreuzer-dsr.de/kdsr/bulletin/KDSR_HypotronTheory_Flyer.pdf and http://kreuzer-dsr.de/kdsr/test/KDSR-PRS-02/KIPS/START-AND-RUN.htm ) nuclei are allowed to contain anti-neutrons as well or even anti-neutrons only. Furthermore it is assumed that annihilation does not occur under all circumstances, but in collisions of particles with almost central impact.
Therefore, there would be no anti-iron but simply iron in the outer region of a pulsar.
The fact that a decaying nucleus ejects a neutron is considered as a result of a reaction (anti-neutron)+(neutrino)-->(neutron)+(anti-neutrino) INSIDE the nucleus which occurs randomly and which is considered to cause the decay.
If a pulsar is not bombarded by neutrinos (emitted by another star) the reaction (anti-neutron)+(neutrino)-->(neutron)+(anti-neutrino) cannot happen inside the pulsar. This might 'explain' why a pulsar does not decay like a nucleus, in contrast to nuclei on earth, which is permanently bombarded by neutrinos.
Dear Karl,
The assumptions (1) and (2) are standard, and corroborated by all accelerator experiments so far.
Dear Patrick,
It is well known to me that assumptions (1) and (2) are considered to be 'standard'. Nevertheless, they can be doubted, because it seems, at least to me, that there is a good reason for that -- otherwise I would'nt have asked this question.
Remark concerning assumption (2):
In accelerator experiments the collision of a charged particle (electron/proton/positron/antiproton) with its corresponding anti-particle or with an atom or a molecule is a collision at (relatively) low or high energy of at least one of the interacting objects, i.e. projectile (particle or anti-particle) and target (atom or molecule) or projectile (particle) and projectile (anti-particle). If in such a collision there is a process observed which can be interpreted as the consequence of an annihilation of a particle and its corresponding antiparticle then such an annihilation process should be considered in the concrete context of the specific kinematic and geometric characteristics of the collision process. To infer that annihilation under some specific circumstances implies annihilation under all circumstances is, at least to my point of view, a generalization which cannot be accepted without any doubts.
Remark concerning assumption (1):
If a nucleus ejects a neutron, then how can it be ensured (experimentally) that this particle existed as a neutron inside the nucleus befor the process of ejection? How can it be ensured (experimentally) that the ejected neutron is not the result of the assumed (randomly occuring) process (anti-neutron)+(neutrino)-->(neutron)+(anti-neutrino) INSIDE the nucleus, being aware that it is extremly difficult to 'observe' neutrino processes at all and being aware that on earth everything is hit permanently by neutrinos from the sun? If the process (anti-neutron)+(neutrino)-->(neutron)+(anti-neutrino) INSIDE the nucleus would be a fact of reality and if such a process finally causes the decay of specific nuclei, then this would dramatically change the 'standards' of contemporary physics in many respects, even in the field of astronomic objects, i.e. a pulsar would have to be identified as an anti-neutron star instead of a neutron star.
i believe soon yes, LISA is an instrument which should be able to discriminate between neutron star mergers and antineutron star mergers IF there are any differences as suggested by: [attached files]
of course, if there are no differences or if there are no populations of antineutron stars extant, then NO. we should know in less than 17 years = 'soon'. regards, sgm
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