arXiv subjects

B. C. Guntsche

Publications and source records attributed to B. C. Guntsche.

5 recordsLinked to original sources

arXiv2026

Pair creation amplitudes for a real scalar field coupled to a time-dependent surface in d+1 dimensions

We study the pair creation phenomenon for a real scalar field $\varphi$ in the presence of a surface that undergoes time-dependent deformations, while imposing Dirichlet-like boundary conditions. Including terms up to fourth order in the departure of the surface from an infinite plane, we present results for the angular dependence of the emission rate for the vacuum-to-pair process as a function of the geometry and the dynamics of the surface, as well as of the momenta of the emitted pair. We check the consistency of the leading contribution with previous results obtained from the imaginary part of the effective action, and clarify how the relation between exclusive probabilities and the imaginary part of the effective action is modified at fourth order by the opening of a two-pair channel.

hep-th↗

arXiv2026

Covariant extrinsic curvature expansion of the nonlocal effective action for a massless scalar field on a manifold with boundary

We study the nonlocal effective action of a massless scalar field defined on a flat manifold with a curved boundary. Using a heat-kernel approach, we derive a covariant expansion of the nonlocal contribution to quadratic order in the extrinsic curvature tensor. Our construction provides a geometric framework that both reproduces earlier results obtained for Monge-patch embeddings and extends them to more general surfaces that need not admit a global Monge-patch description. The expansion is valid in the regime where gradients of the extrinsic curvature dominate over nonlinear curvature effects. As an application, we compute the particle-creation rate for an oscillating deformed ring in $2+1$ dimensions and an oscillating deformed sphere in $3+1$ dimensions.

hep-th↗

arXiv2026

Dynamical Casimir effect in the worldline formulation

We evaluate the effective action for the Dynamical Casimir Effect (DCE) for a real scalar field in $d+1$ dimensions within the worldline formulation of quantum field theory. The scalar field is coupled to a spacetime-dependent mass term, which here plays the role of the moving medium and imposes imperfect boundary conditions on time-dependent surfaces. Expanding in powers of the departure of the geometry from a planar configuration, the worldline path integral factorizes into simpler, lower-dimensional ones. In the limit of a strong coupling to the surface, we recover the Dirichlet result and derive the systematic corrections in inverse powers of the coupling, calculating the imaginary part of the effective action up to arbitrary order of said powers. Finally, we also apply the method to a two-surface configuration.

hep-th↗

arXiv2025

Quantum dissipative effects for a real scalar field coupled to a dynamical Neumann surface in d+1 dimensions

We study dissipative effects for a system consisting of a massless real scalar field satisfying Neumann boundary conditions on a space and time-dependent surface, in d+1 dimensions. We focus on the comparison of the results for this system with the ones corresponding to Dirichlet conditions, and the same surface space-time geometry. We show that, in d=1, the effects are equal up to second order for rather arbitrary surfaces, and up to fourth order for wavelike surfaces. For d>1, we find general expressions for their difference.

hep-th↗

arXiv2024

Quantum dissipative effects for a real scalar field coupled to a time-dependent Dirichlet surface in d+1 dimensions

We study the Dynamical Casimir Effect (DCE) for a real scalar field $\varphi$ in $d+1$ dimensions, in the presence of a mirror that imposes Dirichlet boundary conditions and undergoes time-dependent motion or deformation. Using a perturbative approach, we expand in powers of the deviation of the mirror's surface $\Sigma$ from a hyperplane, up to fourth order. General expressions for the probability of pair creation induced by motion are derived, and we analyze the impact of space-time dimensionality as well as of the non-linear effects introduced by the fourth-order terms.

hep-th↗