124 research outputs found

    Unstable Semiclassical Trajectories in Tunneling

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    Some tunneling phenomena are described, in the semiclassical approximation, by unstable complex trajectories. We develop a systematic procedure to stabilize the trajectories and to calculate the tunneling probability, including both the suppression exponent and prefactor. We find that the instability of tunneling solutions modifies the power-law dependence of the prefactor on h as compared to the case of stable solutions.Comment: Journal version; 4 pages, 2 figure

    Theta--instantons in SU(2) Higgs theory

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    We consider topology changing processes in SU(2)--Higgs theory. In the Standard Model of particle physics they are accompanied by baryon--and lepton--number non--conservation. At fixed energy and multiplicity of initial state, these processes are described by classical Theta--instanton solutions. We describe these solutions and calculate the suppression exponents for the probabilities of the topology changing transitions at relatively low energies.Comment: 12 pages, 5 figure

    Analytic description of monodromy oscillons

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    We develop precise analytic description of oscillons - long-lived quasiperiodic field lumps - in scalar field theories with nearly quadratic potentials, e.g. the monodromy potential. Such oscillons are essentially nonperturbative due to large amplitudes, and they achieve extreme longevities. Our method is based on a consistent expansion in the anharmonicity of the potential at strong fields, which is made accurate by introducing a field-dependent "running mass." At every order, we compute effective action for the oscillon profile and other parameters. Comparison with explicit numerical simulations in (3+1)-dimensional monodromy model shows that our method is significantly more precise than other analytic approaches.Comment: 9 pages, 9 figures; v2: Introduction, Sec. 4 and Discussion extended; journal versio

    Numerical study of multiparticle production in λϕ4\lambda\phi^4 theory

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    We study multiparticle production in the unbroken (3+1)(3+1)-dimensional λϕ4\lambda\phi^4 theory using the semiclassical method of singular solutions. We show that the probabilities of these processes are exponentially suppressed in terms of a small coupling constant λ1\lambda \ll 1 if the multiplicity of the final state is large: n1n \gg 1. At nλ1 n \ll \lambda^{-1} the probabilities agree with well-known perturbative results. At nλ1 n \gg \lambda^{-1} they are dominated by loop effects and decrease exponentially with nn, as we show for the first time.Comment: 7 pages, 2 figures. A contribution to International Conference on Quantum Field Theory, High-Energy Physics, and Cosmology, 18-21 July 2022, Dubna, Russian Federatio

    Soliton-antisoliton pair production in particle collisions

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    We propose general semiclassical method for computing the probability of soliton-antisoliton pair production in particle collisions. The method is illustrated by explicit numerical calculations in (1+1)-dimensional scalar field model. We find that the probability of the process is suppressed by an exponentially small factor which is almost constant at high energies.Comment: 4 pages, 3 figures, journal versio
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