604 research outputs found
What happens to Q-balls if is so large?
In the system of a gravitating Q-ball, there is a maximum charge inevitably, while in flat spacetime there is no upper bound on in
typical models such as the Affleck-Dine model. Theoretically the charge is
a free parameter, and phenomenologically it could increase by charge
accumulation. We address a question of what happens to Q-balls if is close
to . First, without specifying a model, we show analytically
that inflation cannot take place in the core of a Q-ball, contrary to the claim
of previous work. Next, for the Affleck-Dine model, we analyze perturbation of
equilibrium solutions with by numerical analysis of
dynamical field equations. We find that the extremal solution with and unstable solutions around it are "critical solutions", which means
the threshold of black-hole formation.Comment: 9 pages, 10 figures, results for large added, to appear in
PR
Stability of Q-balls and Catastrophe
We propose a practical method for analyzing stability of Q-balls for the
whole parameter space, which includes the intermediate region between the
thin-wall limit and thick-wall limit as well as Q-bubbles (Q-balls in false
vacuum), using the catastrophe theory. We apply our method to the two concrete
models, and
. We find that and Models
fall into {\it fold catastrophe} and {\it cusp catastrophe}, respectively, and
their stability structures are quite different from each other.Comment: 9 pages, 4 figures, some discussions and references added, to apear
in Prog. Theor. Phy
Optimal supply against fluctuating demand
Sornette et al. claimed that the optimal supply does not agree with the
average demand, by analyzing a bakery model where a daily demand fluctuates
with a uniform distribution. In this note, we extend the model to general
probability distributions, and obtain the formula of the optimal supply for
Gaussian distribution, which is more realistic. Our result is useful in a real
market to earn the largest income on average.Comment: 2 page
How does gravity save or kill Q-balls?
We explore stability of gravitating Q-balls with potential
via catastrophe
theory, as an extension of our previous work on Q-balls with potential
. In flat spacetime
Q-balls with in the thick-wall limit are unstable and there is a minimum
charge , where Q-balls with are nonexistent.
If we take self-gravity into account, on the other hand, there exist stable
Q-balls with arbitrarily small charge, no matter how weak gravity is. That is,
gravity saves Q-balls with small charge. We also show how stability of Q-balls
changes as gravity becomes strong.Comment: 10 pages, 10 figure
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