151 research outputs found
Path integral in a magnetic field using the Trotter product formula
The derivation of the Feynman path integral based on the Trotter product
formula is extended to the case where the system is in a magnetic field.Comment: To appear in the American Journal of Physics, 200
No axions from the Sun
Preliminary evidence of solar axions in XMM-Newton observations has quite
recently been claimed by Fraser et al. as an interpretation of their detection
of a seasonally-modulated excess of the X-ray background. Within such an
interpretation, these authors also estimate the axion mass to be eV. Since an axion with this mass behaves as a cold dark
matter particle, according to the proposed interpretation the considered
detection directly concerns cold dark matter as well. So, the suggested
interpretation would lead to a revolutionary discovery if confirmed.
Unfortunately, we have identified three distinct problems in this
interpretation of the observed result of Fraser et al. which ultimately imply
that the detected signal - while extremely interesting in itself - cannot have
any relation with hypothetical axions produced by the Sun. Thus, a physically
consistent interpretation of the observed seasonally-modulated X-ray excess
still remains an exciting challenge.Comment: 3 pages, 1 figure, accepted for publication in MNRA
Periodic Orbit Quantization beyond Semiclassics
A quantum generalization of the semiclassical theory of Gutzwiller is given.
The new formulation leads to systematic orbit-by-orbit inclusion of higher
contributions to the spectral determinant. We apply the theory to
billiard systems, and compare the periodic orbit quantization including the
first contribution to the exact quantum mechanical results.Comment: revte
Astrophysical hints of axion-like particles
After reviewing three astrophysical hints of the existence of axionlike particles (ALPs), we describe in more detail a new similar hint involving flat spectrum radio quasars (FSRQs). Detection of FSRQs above about 20GeV pose a challenge to very-high-energy (VHE) astrophysics, because at those energies the ultraviolet emission from their broad line region should prevent photons produced by the central engine to leave the source. Although a few astrophysical explanations have been put forward, they are totally ad hoc. We show that a natural explanation instead arises within the conventional models of FSRQs provided that photon-ALP oscillations occur inside the source. Our analysis takes the FSRQ PKR 1222+206 as an example, and it looks tantalizing that basically the same choice of the free model parameters adopted in this case is consistent with those that provide the other three hints of the existence of ALPs
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