6,286 research outputs found

    Unstable Hadrons in Hot Hadron Gas in Laboratory and in the Early Universe

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    We study kinetic master equations for chemical reactions involving the formation and the natural decay of unstable particles in a thermal bath. We consider the decay channel of one into two particles, and the inverse process, fusion of two thermal particles into one. We present the master equations the evolution of the density of the unstable particles in the early Universe. We obtain the thermal invariant reaction rate using as an input the free space (vacuum) decay time and show the medium quantum effects on π+πρ\pi+\pi \leftrightarrow \rho reaction relaxation time. As another laboratory example we describe the K+KϕK+K \leftrightarrow \phi process in thermal hadronic gas in heavy-ion collisions. A particularly interesting application of our formalism is the π0γ+γ\pi^{0}\leftrightarrow \gamma +\gamma process in the early Universe. We also explore the physics of π±\pi^{\pm} and μ±\mu^{\pm} freeze-out in the Universe.Comment: 13 pages, 9 figures, published in Physical Review

    Detecting the harmonics of oscillations with time-variable frequencies

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    A method is introduced for the spectral analysis of complex noisy signals containing several frequency components. It enables components that are independent to be distinguished from the harmonics of nonsinusoidal oscillatory processes of lower frequency. The method is based on mutual information and surrogate testing combined with the wavelet transform, and it is applicable to relatively short time series containing frequencies that are time variable. Where the fundamental frequency and harmonics of a process can be identified, the characteristic shape of the corresponding oscillation can be determined, enabling adaptive filtering to remove other components and nonoscillatory noise from the signal. Thus the total bandwidth of the signal can be correctly partitioned and the power associated with each component then can be quantified more accurately. The method is first demonstrated on numerical examples. It is then used to identify the higher harmonics of oscillations in human skin blood flow, both spontaneous and associated with periodic iontophoresis of a vasodilatory agent. The method should be equally relevant to all situations where signals of comparable complexity are encountered, including applications in astrophysics, engineering, and electrical circuits, as well as in other areas of physiology and biology

    PVLAS experiment, star cooling and BBN constraints: Possible interpretation with temperature dependent gauge symmetry breaking

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    It is known that the kinetic mixing of photon and another U(1)_ex gauge boson can introduce millicharged particles. Millicharged particles ff of mass 0.1 eV can explain the PVLAS experiment. We suggest a temperature dependent gauge symmetry breaking of U(1)_ex for this idea to be consistent with astrophysical and cosmological constraints.Comment: 9 pages, 3 figue
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