Mitsuo I. Tsumagari

Publications (4)0 Total impact

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  Available from: ArXiv

  Article: The Physics of Q-balls

  Mitsuo I. Tsumagari
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  ABSTRACT: In this thesis we investigate the stationary properties and formation process of a class of nontopological solitons, namely Q-balls. We explore both the quantum-mechanical and classical stability of Q-balls that appear in polynomial, gravity-mediated and gauge-mediated potentials. By presenting our detailed analytic and numerical results, we show that absolutely stable non-thermal Q-balls may exist in any kinds of the above potentials. The latter two types of potentials are motivated by Affleck-Dine baryogenesis, which is one of the best candidate theories to solve the present baryon asymmetry. By including quantum corrections in the scalar potentials, a naturally formed condensate in a post-inflationary era can be classically unstable and fragment into Q-balls that can be long-lived or decay into the usual baryons/leptons as well as the lightest supersymmeric particles. This scenario naturally provides the baryon asymmetry and the similarity of the energy density between baryons and dark matter in the Universe. Introducing detailed lattice simulations, we argue that the formation, thermalisation and stability of these Q-balls depend on the properties of models involved with supersymmetry breaking. Comment: Ph.D. thesis, University of Nottingham, 156 pages (2009), Advisor: Edmund J. Copeland
  10/2009;
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  Available from: ArXiv

  Article: Affleck-Dine dynamics, Q-ball formation, and thermalization

  Mitsuo I. Tsumagari
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  ABSTRACT: We present both analytically and numerically a consistent analysis of the dynamics from the Affleck-Dine (AD) mechanism to the subsequent semiclassical evolution in both gravity-mediated and gauge-mediated models. We obtain analytically the elliptic motions in the AD dynamics as the analogy of the well-known Kepler-problem, and by solving the equations of motion on a lattice, we find that the semiclassical evolution goes through three distinct stages as a nonequilibrium process of reheating the Universe: prethermalization, bubble collisions and thermalization. We report that the second stage of our case lasts rather long compared to the second stage of the reheating case, and the thermalization process is unique due to the presence of “thermal Q-balls”.
  Phys. Rev. D. 10/2009; 80(8).
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  Available from: ArXiv

  Article: Q-balls in flat potentials

  Edmund J. Copeland, Mitsuo I. Tsumagari
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  ABSTRACT: We study the classical and absolute stability of Q-balls in scalar field theories with flat potentials arising in both gravity-mediated and gauge-mediated models. We show that the associated Q-matter formed in gravity-mediated potentials can be stable against decay into their own free particles as long as the coupling constant of the nonrenormalisable term is small, and that all of the possible three-dimensional Q-ball configurations are classically stable against linear fluctuations. Three-dimensional gauge-mediated Q-balls can be absolutely stable in the "thin-wall-like" limit, but are completely unstable in the "thick-wall" limit. Comment: 26 pages, 25 figures
  05/2009;
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  Available from: ArXiv

  Article: Some stationary properties of a $Q$-ball in arbitrary space dimensions

  Mitsuo I. Tsumagari, Edmund J. Copeland, Paul M. Saffin
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  ABSTRACT: Introducing new physically motivated ans\"{a}tze, we explore both analytically and numerically the classical and absolute stabilities of a single $Q$-ball in an arbitrary number of spatial dimensions $D$, working in both the thin and thick wall limits.
  06/2008;