1,721,067 research outputs found
Testing nucleation theory in two dimensions
No full textWe calculate bubble-nucleation rates for (2+1)-dimensional scalar theories at high temperature, Our approach is based on the notion of a real coarse-grained potential, The region of applicability of our method is determined through internal consistency criteria. We compare our results with data from lattice simulations. Good agreement is observed when the renormalized action of the simulated theory is known. (C) 1999 Elsevier Science B,V, All rights reserved
A consistent calculation of bubble-nucleation rates
No full textWe present a consistent picture of tunnelling in field theory. Our results apply both to high-temperature field theories in four dimensions and to zero-temperature three-dimensional ones. Our approach is based on the notion of a coarse-grained potential U-k that incorporates the effect of fluctuations with characteristic momenta above a given scale k. U-k is non-convex and becomes equal to the convex effective potential for k --> 0. We demonstrate that a consistent calculation of the nucleation rate must be performed at non-zero values of k, larger than the typical scale of the saddle-point configuration that dominates tunnelling. The nucleation rate is exponentially suppressed by the action S-k Of this Saddle point. The pre-exponential factor A(k), which includes the fluctuation determinant around the saddle-point configuration, is well-defined and finite. Both S-k and A(k) are k-dependent, but this dependence cancels in the expression for the nucleation rate. This picture breaks down in the limit of very weakly first-order phase transitions, for which the pre-exponential factor compensates the exponential suppression. (C) 1999 Elsevier Science B.V
Erratum: The renormalization of fluctuating branes, the Galileon and asymptotic safety (Journal of High Energy Physics (2013) 04, (036))
No full textThe region of validity of homogeneous nucleation theory
No full textWe examine the region of validity of Langer's picture of homogeneous nucleation. Our approach is based on a coarse-grained free energy that incorporates the effect of fluctuations with momenta above a scale k, The nucleation rate I = A(k)exp(-S-k) is exponentially suppressed by the action S-k of the saddle-point configuration that dominates tunnelling. The factor A(k) includes a fluctuation determinant around this saddle point. Both S-k and A(k) depend on the choice of k, but, for 1/k close to the characteristic length scale of the saddle point, this dependence cancels in the expression for the nucleation rate. For very weak first-order phase transitions or in the vicinity of the spinodal decomposition line, the pre-exponential factor A(k) compensates the exponential suppression exp(-S-k). In these regions the standard nucleation picture breaks down. We give an approximate expression for A(k) in terms of the saddle-point profile, which can be used for quantitative estimates and practical tests of the validity of homogeneous nucleation theory, (C) 1999 Elsevier Science B.V. All rights reserved
Anomalous anomalous scaling?
No full textMotivated by speculations about infrared deviations from the standard behavior of local quantum field theories, we explore the possibility that such effects might show up as an anomalous running of coupling constants. The most sensitive probes are presently given by the anomalous magnetic moments of the electron and the muon, that suggest that alpha(em) runs 1.00047 +/- 0.00018 times faster than predicted by the Standard Model. The running of alpha(em) and alpha(s) up to the weak scale is confirmed with a precision at the % level. (C) 2008 Elsevier B.V. All rights reserved
The renormalization of fluctuating branes, the Galileon and asymptotic safety
Full text linkWe consider the renormalization of d-dimensional hypersurfaces (branes) embedded in flat (d + 1)-dimensional space. We parametrize the truncated effective action in terms of geometric invariants built from the extrinsic and intrinsic curvatures. We study the renormalization-group running of the couplings and explore the fixed-point structure. We find evidence for an ultraviolet fixed point similar to the one underlying the asymptotic-safety scenario of gravity. We also examine whether the structure of the Galileon theory, which can be reproduced in the nonrelativistic limit, is preserved at the quantum level. © 2013 SISSA, Trieste, Italy
Quantum corrections in Galileon theories
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Bubble-Nucleation Rates for Radiatively Induced First-Order Phase Transitions
No full textWe present a consistent calculation of bubble-nucleation rates in theories of two scalar fields. Our approach is based on the notion of a coarse-grained free energy that incorporates the effects of fluctuations with momenta above a given scale k. We establish the reliability of the method for a variety of two-scalar models and confirm the conclusions of previous studies in one-field theories: Langer's theory of homogeneous nucleation is applicable as long as the expansion around the semiclassical saddle point associated with tunnelling is convergent. This expansion breaks down when the exponential suppression of the rate by the saddle-point action becomes comparable to the pre-exponential factor associated with fluctuations around the saddle point. We reconfirm that Langer's theory is not applicable to the case of weakly first-oder phase transitions. We also find that the same is true in general for radiatively induced first-order phase transitions. We discuss the relevance of our res..
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