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Diego Saviot
Diego Saviot
Title of the talk:
Strong-field regime within effective field theory
Abstract:
In this talk, I present an expansion of the effective action obtained when integrating out scalar QED in presence of a strong-field background. The computation is carried out in momentum space by adapting the framework of Covariant Derivative Expansion to capture non-perturbative effects. I will draw parallels with the worldline formalism both to guide the way and to compute Green functions.
I eventually specialise to the case of small inhomogeneities of a strong background and compute the first correction to the Heisenberg-Euler effective action in a derivative expansion.
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André Gontijo Campos
André Gontijo Campos
Title of the talk:
Strong-field regime within effective field theory Laboratory cosmology with free spinorial wave packets
Abstract:
The electron quantum dynamics at crossing the black hole horizon is investigated. Exploiting the equivalence principle, we show a way to emulate the electron’s dynamics via an appropriately chirped free electron wave packet, where the dynamical characteristics is encoded in the interference fringes of the wave packet. Apart from creating an analog of the gravitational effect, we deduce the electron’s explicit wavefunction at the horizon of a black hole and provide quantitative predictions on the quantum properties of the electron crossing the horizon.
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Mohammed Alkhateeb
Mohammed Alkhateeb
Title of the talk:
Computational Quantum Field Theory for Fermionic Pair Production in 1+1 Dimensions
Abstract:
Computational quantum field theory (CQFT) provides a real-time numerical framework for studying quantum field dynamics in strong, space- and time-dependent external backgrounds beyond perturbation theory. In this talk, I will first introduce the CQFT formalism in flat spacetime, demonstrating how the time evolution of first-quantized states can be used to evaluate QFT time-dependent observables such as charge densities and currents, as well as how CQFT might address the ambiguity problem of particle number at transient times.
I will then present an extension of this framework to quantum fields in curved spacetime, focusing on fermionic fields in 1+1-dimensional gravitational backgrounds. Using the vielbein formalism, I provide an effective Dirac Hamiltonian for a prescribed curved geometry and show how an appropriate field rescaling leads to a Hermitian Hamiltonian and unitary time evolution. This enables the direct numerical simulation of vacuum excitation and fermion–antifermion pair creation induced by spacetime curvature.
As an illustration, I will discuss results for a smooth, asymptotically flat spacetime generated by a localized Gaussian curvature deformation, introduced into the Minkowski vacuum as a quench. The evolution of particle number densities and total particle production is analyzed, highlighting the role of curvature strength and spatial extension and the Pauli blockade.
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worldliners2026.pdfDavide Rovere
Davide Rovere
Title of the talk:
Worldline Formulations of Covariant Fracton Theories
Abstract:
Fractons first appeared in spin lattice models as quasiparticle excitations characterised by reduced mobility, due to the conservation of the dipole moment. The so-called "covariant fracton gauge theories" are a family of Lorentz-covariant extensions of the gauge theory of fractons, which can be viewed as a generalisation of linearised Einstein gravity. In this talk, based on the paper arXiv:2508.14591 with F. Fecit, some worldline formulations of covariant fracton gauge theories will be presented, based on additional bosonic coordinates to the phase space. These models allow for the BV spectrum of covariant fracton gauge theories to be obtained, from the spacetime perspective, in a completely covariant way, through the BRST quantisation of the classical phase space. The possibility of deriving covariant fracton gauge theories from a worldline perspective is a further confirmation of the worldline/spacetime duality of gauge theories in BV formulation.
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Azadeh Maleknejad
Azadeh Maleknejad
Title of the talk:
The Stochastic Schwinger Effect
Abstract:
The Schwinger effect predicts nonperturbative particle–antiparticle pair production in a strong classical electric field. In realistic environments, however, gauge fields are rarely coherent or constant — they are transient, inhomogeneous, and often stochastic. In this talk, I introduce a new type of Schwinger effect, which we call the stochastic Schwinger effect. We formulate vacuum decay in statistically fluctuating gauge-field backgrounds and compute the decay rate and particle number density using the effective action formalism, obtaining closed analytical results for both scalars and fermions. Working in flat spacetime and at zero temperature to isolate the core physics, we demonstrate that stochastic fluctuations themselves can drive vacuum instability. This framework opens a new avenue for understanding particle production in early-Universe and high-energy astrophysical settings.
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Emil Akhmedov
Emil Akhmedov
Title of the talk:
Does Schwinger's value for the current of created pairs gets modified for long and strong enough pulse?
Abstract:
We determine the parametric conditions (pulse strength and duration) under which Schwinger's prediction for the pair-creation current - and therefore the probability - is significantly altered. Then we will discuss the possibility of an avalanche of particle creation in external fields and similar phenomena in background fields of other nature.
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Mohammad Alminawi
Mohammad Alminawi
Title of the talk:
Combinatorics of S-matrix Invariance under Field Redefinitions
Abstract:
Invariance of on-shell scattering amplitudes under field redefinitions is a well known property in field theory that corresponds to covariance of on-shell amputated connected functions. In this talk I will showcase the combinatorics behind the covariance of on-shell amputated connected functions at the tree and 1-loop level using properties of the classical action for an arbitrary theory, as well as proving the existence of covariant Feynman rules and establishing the framework for generalizing the proof to higher loop orders.
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Mateja Boskovic
Mateja Boskovic
Title of the talk:
Worldline effective field theory for gravitational atoms
Abstract:
Superradiant instabilities of rotating black holes can give rise to extended bosonic clouds surrounding them, thus forming “gravitational atoms”. These long-lived structures serve as natural laboratories for probing a wide range of parameter space for putative ultralight bosons in nature. The presence of a companion can significantly modify both the cloud's evolution and the orbital dynamics, leaving a trail of feedback effects that require detailed modeling. I will describe a systematic framework, based on a worldline effective field theory approach, to model the orbital dynamics of such binaries, including both eccentricity and spin–orbit misalignment. I will further describe phenomenological signatures that occur both in the band of future gravitational-wave detectors as well as indirect signatures in the distribution of orbital elements of binary black holes—both within reach of upcoming observatories such as LISA and the Einstein Telescope.
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worldline_slides.pdfGregorio Paci
Gregorio Paci
Title of the talk:
Trace Anomalies from Conformal Geometry
Abstract:
Trace anomalies provide a powerful window into the structure of quantum field theories, containing information on flat space correlators that can be encoded in an effective action induced by the anomaly.
They also play a role in a variety of physical contexts, ranging from black hole physics to condensed matter systems.
In this talk, I will start with a general overview on trace anomalies. I will then present a geometric approach, known as the ambient space formalism, which offers a very useful way to think about these anomalies by embedding the theory in a higher-dimensional space. From this perspective, I will outline a systematic procedure to construct trace anomalies and their associated effective actions in arbitrary even dimensions, as developed in arXiv:2411.03842, and discuss both the strengths and the limitations of this method.
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Worldline_seminars_GP.pdfEugenia Boffo
Eugenia Boffo
Title of the talk:
Classical BV cohomology of the spinning particle
Abstract:
The Batalin-Vilkovisky formalism is based on cochain complexes, graded by ghost degree, with a shifted Poisson bracket. A natural postulate in physics (Henneaux and Teitelboim, 1992, and later on Felder and Kazhdan, 2014) is the absence of cohomology in negative ghost degrees owing to the fields in non-positive ghost degree. In this talk, we show that some cohomology classes incompatible with the above axiom, found by Getzler in 2016 in a classical system of physical interest, the spinning particle, are actually removed by a resolution of the reducibile constraints, thereby confirming that the spinning particle satisfies the axiom. Based on the preprint 2510.00655 with Cederwall.
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Spinning_particle__cohomology.pdfMichel Manon
Michel Manon
Title of the talk:
Leveraging non-reversible Markov processes for efficient sampling
Abstract:
Non-reversible Markov processes have emerged as a powerful alternative to traditional reversible MCMC methods, enabling faster exploration by reducing diffusive backtracking. In this talk, I will introduce the main ideas behind such approaches, focusing on lifting techniques, event-chain Monte Carlo (ECMC), and piecewise deterministic Markov processes (PDMPs). I will present a unifying perspective based on augmented state spaces, global symmetries and directed probability flows, highlighting how these constructions improve sampling efficiency and connect seemingly different algorithms.
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Patrick Copinger
Patrick Copinger
Title of the talk:
In-in worldline formalism in pair creating fields
Abstract:
In strong-field quantum electrodynamics in-out scattering matrix elements are easily
represented using first quantized techniques, such as the worldline formalism. However, out-of-equilibrium observables using an in-in or closed time path construction are less well-known. I discuss ongoing efforts to define such observables using a first quantized approach.
The in-in worldline formalism is derived using two approaches: from the Bogoliubov
coefficients and from the Schwinger-Keldysh closed time path. Augmentations to in-out
formalism amount to the insertion of a non-local interaction term that serves to pick up
singularities in the imaginary Schwinger propertime plane associated with Schwinger pair production. I further discuss a resummation scheme for the in-in generating functional leading to a worldline representation for the exact N-particle generation probability in an arbitrary background field.
[PC, S. Pu, (2025) 2512.19264.]
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Worldliners_Conference.pdfJohannes Pirsch
Johannes Pirsch
Title of the talk:
Higher spin from supersymmetric worldlines and gravitational scattering
Abstract:
In this talk I will present our latest work on extending the method of Generalized Wilson lines to higher orders in spin. A key aspect of this work is a technique for constructing supersymmetric worldline models that capture the rotational degrees of freedom of compact astrophysical objects while evading the known no-go theorems. Deforming the supersymmetry transformation in a particular way will shed light on the dynamics of rotating black holes and Neutron stars in arbitrary gravitational backgrounds. Equipped with worldline models of spinning particles we will construct the first quantized path integrals in the classical limit which are essential building blocks for classical black hole scattering processes.
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Gerald Dunne
Gerald Dunne
Title of the talk:
Heisenberg-Euler and the Quantum Dilogarithm
Abstract:
I describe a new dispersion integral representation of the well-known Heisenberg-Euler one-loop QED effective action. Thus, the imaginary part determines the real part, and vice versa. This physical fact is not directly manifest in the standard integral representations. The dispersive expression is in terms of the quantum dilogarithm, a special q-function which has found many applications in physics and mathematics since its introduction in the 1990s by Faddeev and others. Many of the quantum dilogarithm's somewhat exotic properties turn out to have a natural interpretation from the QED perspective. The dispersive representation also provides simple numerical evaluation as a function of both field invariants when the background field has both magnetic and electric components, and enables the analytic study of a variety of physical limits.
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dunne_worldline_2026_qdilog.pdfDaniel Steck
Daniel Steck
Title of the talk:
Worldline methods for scalar electromagnetic Casimir potentials
Abstract:
The development of new, general methods for the computation of Casimir potentials in arbitrary geometries and for arbitrary material properties remains a difficult problem. I will review our recent work on the world-line method, previously developed for scalar fields coupled to background potentials. This is a path-integral Monte-Carlo method for computing vacuum- and thermal-state energies of the field. Our work focuses on the generalization of this method to electromagnetism. I will review our recent results in considering scalar electromagnetic fields coupled to dielectrics, where we are able to reproduce a number of classic Casimir-potential results within a general framework. I will also briefly review the path towards a generalization to a full vector-electromagnetism formalism.
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John Joseph Carrasco
John Joseph Carrasco
Title of the talk:
The Double-Copy Origin of Hawking Thermality
Abstract:
The double copy relates gravity to gauge theory, but how does this extend to semiclassical phenomena such as Hawking radiation? I will show that the thermal spectrum of a collapsing black hole admits a gauge-theory origin: classical non-abelian sources radiate in a way that is thermal in color charge. This correspondence emerges both from an S-matrix description of particle production and from a complementary one-loop effective action analysis, mapping horizon thermodynamics to simple properties of color charge.
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rootThermalityWorldline_small.pdfSree Mahesh Chandran
Sree Mahesh Chandran
Title of the talk:
Entanglement Scaling and Dynamics in the Sauter-Schwinger Effect
Abstract:
In quantum field theory, entanglement entropy under spatial bipartitioning serves as a powerful information-theoretic probe of quantum correlations. In this talk, I will present the first comprehensive numerical study of the dynamical evolution and geometric scaling of entanglement entropy in a nonperturbative, strong-field QED setting --- specifically, in the context of the Sauter-Schwinger effect. While the weak-field regime is dominated by area-law states, the entanglement entropy is shown to undergo a transition from area-law to a near-volume-law scaling for certain strong-field regimes in the pulse-profile parameter space --- signaling a fundamental shift in the underlying correlation structure driven by nonperturbative pair production. For intermediate regimes, the scaling is a power-law that interpolates between the two extremes. I will provide interpretations based on the behavior of the low-energy pair-creation spectrum as well as the effective penetration depth for correlations, and discuss how these insights could inform future investigations of related phenomena.
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2026_Worldline_Seminars (9).pdfAntonino Di Piazza
Antonino Di Piazza
Title of the talk:
Control of Nonlinear Compton Scattering in a Squeezed Vacuum
Abstract:
Electromagnetic radiation by accelerated charges is a fundamental process in physics. Here, we introduce a quantum-optical framework for controlling the emission of radiation of an electron in an intense laser field via squeezed vacuum states. By engineering the quantum fluctuations of the emission modes, we demonstrate that the probability of nonlinear Compton scattering can be significantly enhanced or suppressed through tunable squeezing amplitude and angle. We show numerically that our predictions are experimentally accessible with current squeezing technologies, establishing a new paradigm for quantum control in high-intensity light-matter interactions.
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