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11
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84927445437
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P. Sikivie, in Cosmology and Particle Physics, edited by E. Alvarez et al. (World Scientific, Singapore, 1987), p. 144.
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15
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84927445436
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or, L. L. Krauss, in High Energy Physics 1985, edited by M. Bowick and F. Gursey (World Scientific, Singapore, 1986).
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20
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84927445427
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if the Universe inflated before or during Peccei-Quinn spontaneous symmetry breaking, the limit depends upon the initial misalignment angle to the 1.7 power. If the Universe never underwent inflation, then axion production by the decay of axionic strings may also be a significant source of axions, and may lead to a more stringent lower bound to ma.
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24
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84927445425
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Here it is also shown that for axion masses >wig 0.02 eV axion reabsorption is important, and that for ma>wig 2.2 eV reabsorption reduces axion emission to the extent that such an axion is not precluded by SN1987A.
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31
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84927445423
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J. Wilson, in Numerical Astrophysics, edited by J. Centrella et al. (Jones & Bartlett, Boston, 1984).
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33
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84927445422
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In quoting Iwamoto's axion emission rate, we have corrected it for a forgotten factor of 2 (for identical particles in the initial state).
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34
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84927445421
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Mayle et al. (see Ref. 7) have also computed ε dota(ND). However their rate has the wrong temperature dependence: ε dota(ND, Mayle et al.)~apeq 3.5 times 1048 erg cm-3 secf4-1gan2(Xnρ14)2TMeV3, corresponding to εaprop T6F(y), cf. Eq. (4) and below. We have taken the liberty of correcting the ND emission rate computed in Ref. 6 for a factor of 2 algebra error.
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35
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84927445420
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The limits derived in Ref. 8 cannot be easily compared to those of Refs. 6 and 7, as the authors of Ref. 8 do not explicitly specify the relationship between the axion-nucleon coupling and the axion mass. However, if one infers that relationship, their bound is comparable to that of Ref. 6.
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36
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84927445419
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In obtaining Eq. (5c), the expression for axion emission in the ND limit in terms of rho, Xn, and T, we have used the relationship eyapeq 125Xnρ14TMeV-3/2, which is valid only in the ND limit (y << -1). One might have been tempted to use the exact expression for y, obtained by solving g(y)=111Xnρ14TMeV-3/2, where g(y)= tint0infu1/2du/(eu-y+1). In addition to the obvious fact that ε dota(ND) then could not be written in closed form (except for y << -1), the resulting expression when extrapolated to y >wig 0 gives a larger value for ε dota(ND) which overestimates the true emission rate by a larger factor than Eq. (5c) and does not even decrease monotonically with decreasing temperature (increasing y). The simple limiting form chosen in Eq. (5c) extrapolates to the semidegenerate regime much better, and of course has the same form in the very nondegenerate regime.
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38
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Collapse models without axion emission (see, e.g., Ref. 9) indicate postcollapse, central temperatures of order 30 – 80 MeV. When the effect of axion cooling is self-consistently taken into account, the central core temperature will drop, thereby quenching axion emission. It is necessary to take this into account properly to obtain a reliable limit to the axion mass. The first steps toward this end were taken in Refs. 7 and 8.
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41
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Both the axion and pion are Nambu-Goldstone bosons, and fundamentally have derivative (pseudovector) couplings: axion, (gai/2m) γ5γmu;
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42
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84927445407
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pion (f/mπ) γ5γmu. By appropriate phase rotations of the nucleon fields their derivative couplings can be made to be pseudoscalar couplings: axion, gaiγ5;
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43
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0009094885
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pion, f(2m/mπ) γ5. However, both the axion and pion couplings cannot simultaneously be made pseudoscalar without the introduction of additional contact terms (as also noted in Ref. 8): without additional contact terms only one coupling can be made pseudoscalar. This explains the discrepancy between Iwamoto's work and that of A. Pantziris and K. Kang [, ], who also calculated the matrix element squared for n+n -> n+n+a, and obtained a result that is a factor of (m/T) larger than that of Iwamoto. Iwamoto used a pseudoscalar coupling for the axion and a pseudovector coupling for the pion, while Pantziris and Kang used pseudoscalar couplings for both, and neglected the required contact terms.
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(1986)
Phys. Rev. D
, vol.33
, pp. 3509
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