arXiv subjects

Andreas Weiler

Publications and source records attributed to Andreas Weiler.

At least 19 recordsLinked to original sources

arXiv2026

Baryon Asymmetry from Electroweak-Symmetric Domain Walls

We investigate electroweak baryogenesis from domain walls with electroweak-symmetric cores moving through the electroweak-broken plasma. In the thick-wall regime, CP-violating semiclassical forces generate chiral asymmetries that source baryon number through transport and weak sphaleron processes. We show that the baryon yield is governed by the hierarchy between the wall width, the CP-violating source width, and the diffusion length, and we identify the corresponding scaling behavior in the relevant parametric limits. A distinctive feature of this mechanism is the interference between the two faces of the domain wall, which leads to qualitatively different behavior for CP-violating sources that are even or odd under wall-orientation reversal. We construct a simplified description that captures these effects and reproduces the predictions of the full transport system in a broad range of parameter space. Applying our framework to a singlet-extended Standard Model, we delineate the region in which electroweak-symmetric domain walls can generate the observed baryon asymmetry.

hep-ph↗

arXiv2026

Inverse Electroweak Baryogenesis

We propose a mechanism for baryogenesis in which the baryon asymmetry is generated as an equilibrium response of weak sphalerons in a region where electroweak sphaleron transitions remain unsuppressed, $h/T\lesssim 1$. A nonzero equilibrium baryon density arises in the presence of an approximately conserved global charge, carried either by new states with nonzero hypercharge, or by Standard Model fields themselves. The required global charge asymmetry is generated during a phase transition that changes the strength of electroweak symmetry breaking, but need not coincide with the final electroweak phase transition. In particular, the mechanism can operate during an inverse electroweak phase transition, where baryon number is produced behind the advancing wall, in contrast to conventional electroweak baryogenesis. Because baryon production is decoupled from a direct first-order electroweak phase transition, the scenario can be realized at parametrically higher temperatures than standard electroweak baryogenesis, thereby weakening current experimental constraints. This framework provides a qualitatively distinct route to electroweak baryogenesis, with different parametric dependence, phase-transition dynamics, and phenomenological signatures.

hep-ph↗

arXiv2025

Query Carefully: Detecting the Unanswerables in Text-to-SQL Tasks

Text-to-SQL systems allow non-SQL experts to interact with relational databases using natural language. However, their tendency to generate executable SQL for ambiguous, out-of-scope, or unanswerable queries introduces a hidden risk, as outputs may be misinterpreted as correct. This risk is especially serious in biomedical contexts, where precision is critical. We therefore present Query Carefully, a pipeline that integrates LLM-based SQL generation with explicit detection and handling of unanswerable inputs. Building on the OncoMX component of ScienceBenchmark, we construct OncoMX-NAQ (No-Answer Questions), a set of 80 no-answer questions spanning 8 categories (non-SQL, out-of-schema/domain, and multiple ambiguity types). Our approach employs llama3.3:70b with schema-aware prompts, explicit No-Answer Rules (NAR), and few-shot examples drawn from both answerable and unanswerable questions. We evaluate SQL exact match, result accuracy, and unanswerable-detection accuracy. On the OncoMX dev split, few-shot prompting with answerable examples increases result accuracy, and adding unanswerable examples does not degrade performance. On OncoMX-NAQ, balanced prompting achieves the highest unanswerable-detection accuracy (0.8), with near-perfect results for structurally defined categories (non-SQL, missing columns, out-of-domain) but persistent challenges for missing-value queries (0.5) and column ambiguity (0.3). A lightweight user interface surfaces interim SQL, execution results, and abstentions, supporting transparent and reliable text-to-SQL in biomedical applications.

cs.DB↗

arXiv2025

New ultralight scalar particles and the mass-radius relation of white dwarfs -- the important role of Sirius B

We present the equation of state for two classes of new ultralight particles, a scalar field coupling to electrons and a light $\mathbb{Z}_\mathcal{N}$ QCD axion field coupling to nucleons. Both are potential candidates for dark matter. Using the scalar modified equations of state, we calculate models for white dwarf stars and compare their radii and masses with observed mass-radius data. The comparison results in stringent constraints on the masses of the particles and the coupling parameters. For a wide range of particle masses and coupling parameters, constraints from the white dwarf equation of state surpass existing limits, outperforming also dedicated laboratory searches. The remarkable accuracy of modern white-dwarf mass-radius relation data, exemplified by Sirius B, now allows stringent tests of dense-matter physics and constraints on new particle scenarios.

astro-ph.HE↗

arXiv2025

$\phi$-Dwarfs: White Dwarfs probe Quadratically Coupled Scalars

We study ultralight scalar fields with quadratic couplings to Standard-Model fermions and derive strong constraints from white-dwarf mass-radius data. Such couplings source scalar profiles inside compact stars, shift fermion masses, and can produce a new ground state of matter. We analyze couplings to electrons and to nucleons, incorporating composition and finite-temperature effects in white dwarf structure and equations of state. We identify two robust observables: (i) forbidden gaps - ranges of radii with no stable configurations - and (ii) characteristic shape distortions that drive white dwarf masses toward the Chandrasekhar limit (electron couplings) or shift the maximum mass (nucleon couplings). Confronting these predictions with precise measurements for Sirius B and Procyon B, together with the global white dwarf population, excludes large regions of unexplored parameter space and extends earlier QCD-axion-specific bounds to a broader class of scalar theories. Our stellar constraints rely only on sourcing and do not assume the scalar constitutes dark matter; where mass reductions are small, precision laboratory searches remain competitive. White-dwarf astrophysics thus provides a powerful, largely assumption-minimal probe of ultralight, quadratically coupled scalars.

hep-ph↗

arXiv2025

Renormalising the Field-Space Geometry

We present a systematic study of one-loop quantum corrections in scalar effective field theories from a geometric viewpoint, emphasizing the role of field-space curvature and its renormalisation. By treating the scalar fields as coordinates on a Riemannian manifold, we exploit field redefinition invariance to maintain manifest coordinate independence of physical observables. Focusing on the non-linear sigma model (NLSM) and $\phi^4$ theory, we demonstrate how loop corrections induce momentum- and scale-dependent shifts in the curvature of the field-space manifold. These corrections can be elegantly captured through the recently proposed geometry-kinematics duality, which generalizes the colour-kinematics duality in gauge theories to curved field-space backgrounds. Our results highlight a universal structure emerging in the contractions of Riemann tensors that contribute to renormalisation of the field-space curvature. In particular, we find explicit expressions and a universal structure for the running curvature and Ricci scalar in simple models, illustrating how quantum effects reshape the underlying geometry. This geometric formulation unifies a broad class of scalar EFTs, providing insight into the interplay of curvature, scattering amplitudes, and renormalisation.

hep-th↗

arXiv2024

Minimal Electroweak Baryogenesis via Domain Walls

The Standard Model extended by a real scalar singlet $S$ with an approximate $\mathbb{Z}_2$ symmetry offers a minimal framework for realizing electroweak baryogenesis (EWBG) during a first-order electroweak phase transition. In this work, we explore a novel mechanism where spontaneous $\mathbb{Z}_2$ breaking enables EWBG via domain walls separating two distinct phases of the $S$ field. These domain walls feature restored (or weakly broken) EW symmetry in their cores and sweep through space, generating the baryon asymmetry below the temperature of EW symmetry breaking. We identify the key conditions for the existence of EW-symmetric domain wall cores and analyze the dynamics required for wall propagation over sufficient spatial volumes. Additionally, we outline the CP-violating sources necessary for baryogenesis under different regimes of domain wall evolution. The parameter space accommodating this mechanism spans singlet masses from sub-eV to 15 GeV, accompanied by a non-vanishing mixing with the Higgs boson. Unlike the standard realization of EWBG in the minimal singlet-extended SM, which is notoriously difficult to test, our scenario can be probed by a wide range of existing and upcoming experiments, including fifth force searches, rare meson decays, and EDM measurements.

hep-ph↗

arXiv2024

A Universal Bound on QCD Axions from Supernovae

We identify a new production channel for QCD axions in supernova environments that contributes to axion emissivity for all models solving the strong CP problem. This channel arises at tree-level from a shift-symmetry-breaking operator constructed at next-to-leading order in Chiral Perturbation Theory. In scenarios where model-dependent derivative couplings to nucleons are absent, this sets the strongest model-independent constraint on the axion mass, improving on existing bounds by two orders of magnitude.

hep-ph↗

arXiv2024

From Supernovae to Neutron Stars: A Systematic Approach to Axion Production at Finite Density

We present a systematic study of QCD axion production in environments with finite baryon density and temperature, implying significant changes to axion phenomenology. Within heavy baryon chiral perturbation theory, we derive the effective Lagrangian describing axion interactions with nucleons and mesons up to next-to-leading-order in the chiral expansion. We focus on corrections to the axion-nucleon couplings from higher orders and finite density. These couplings are modified by up to an order of magnitude near nuclear saturation density, significantly impacting axion production in supernovae and neutron stars. Density-dependent corrections enhance the axion luminosity in supernovae by an order of magnitude, strengthening current best bounds by a factor of three. We stress the importance of including all axion production channels up to a given chiral order for a consistent luminosity calculation and classify the missing contributions up to the third chiral order. The modified axion-nucleon couplings also affect neutron star cooling rates via axion emission. A re-evaluation of existing neutron star cooling bounds, constrained to regions where perturbative control is reliable, weakens these bounds by a factor of four. Lastly, our results have implications for terrestrial axion searches that rely on precise knowledge of axion-nucleon couplings.

hep-ph↗

arXiv2024

White dwarfs as a probe of exceptionally light QCD axions

We study the effects of exceptionally light QCD axions on the stellar configuration of white dwarfs. At finite baryon density, the non-derivative coupling of the axion to nucleons displaces the axion from its in-vacuum minimum which implies a reduction of the nucleon mass. This dramatically alters the composition of stellar remnants. In particular, the modifications of the mass-radius relationship of white dwarfs allow us to probe large regions of unexplored parameter space without requiring that axions are dark matter.

hep-ph↗

arXiv2023

Heavy neutron stars from light scalars

We study how light scalar fields can change the stellar landscape by triggering a new phase of nuclear matter. Scalars coupled to nucleons can develop a non-trivial expectation value at finite baryon density. This sourcing of a scalar reduces the nucleon mass and provides an additional energy density and pressure source. Under generic conditions, a new ground state of nuclear matter emerges, with striking implications for the configuration of stellar remnants. Notably, neutron stars in the new ground state can be significantly heavier than QCD equations of state currently predict. We also find hybrid stellar compositions and stable self-bound objects with sizes as small as the Compton wavelength of the scalar. We discuss several specific realizations of this scenario: the QCD axion and lighter generalizations thereof and linearly or quadratically coupled scalar fields effectively equivalent to a class of scalar-tensor modification of gravity. Lastly, we explore phenomenological signatures relevant to electromagnetic and gravitational wave observations of neutron stars, such as atypical compactness and instability gaps in radii.

hep-ph↗

arXiv2023

Electric dipole moments at one-loop in the dimension-6 SMEFT

In this paper we present the complete expressions of the lepton and neutron electric dipole moments (EDMs) in the Standard Model Effective Field Theory (SMEFT), up to 1-loop and dimension-6 level and including both RG running contributions and finite corrections. The latter play a fundamental role in the cases of operators that do not renormalize the dipoles, but there are also classes of operators for which they provide an important fraction, $10-20\%$, of the total 1-loop contribution, if the new physics scale is around $Λ=5$ TeV. We present the full set of bounds on each individual Wilson coefficient contributing to the EDMs using both the current experimental constraints, as well as those from future experiments, which are expected to improve by at least an order of magnitude.

hep-ph↗

arXiv2022

Towards an electrostatic storage ring for fundamental physics measurements

We describe a new table-top electrostatic storage ring concept for $30$ keV polarized ions at frozen spin condition. The device will ultimately be capable of measuring magnetic fields with a resolution of 10$^{-21}$ T with sub-mHz bandwidth. With the possibility to store different kinds of ions or ionic molecules and access to prepare and probe states of the systems using lasers and SQUIDs, it can be used to search for electric dipole moments (EDMs) of electrons and nucleons, as well as axion-like particle dark matter and dark photon dark matter. Its sensitivity potential stems from several hours of storage time, comparably long spin coherence times, and the possibility to trap up to 10$^9$ particles in bunches with possibly different state preparations for differential measurements. As a dark matter experiment, it is most sensitive in the mass range of 10$^{-10}$ to 10$^{-19}$ eV, where it can potentially probe couplings orders of magnitude below current and proposed laboratory experiments.

hep-ex↗

arXiv2021

Advances in Multi-Variate Analysis Methods for New Physics Searches at the Large Hadron Collider

Between the years 2015 and 2019, members of the Horizon 2020-funded Innovative Training Network named "AMVA4NewPhysics" studied the customization and application of advanced multivariate analysis methods and statistical learning tools to high-energy physics problems, as well as developed entirely new ones. Many of those methods were successfully used to improve the sensitivity of data analyses performed by the ATLAS and CMS experiments at the CERN Large Hadron Collider; several others, still in the testing phase, promise to further improve the precision of measurements of fundamental physics parameters and the reach of searches for new phenomena. In this paper, the most relevant new tools, among those studied and developed, are presented along with the evaluation of their performances.

hep-ex↗

arXiv2021

RG of GR from On-shell Amplitudes

We study the renormalization group of generic effective field theories that include gravity. We follow the on-shell amplitude approach, which provides a simple and efficient method to extract anomalous dimensions avoiding complications from gauge redundancies. As an invaluable tool we introduce a modified helicity $\tilde{h}$ under which gravitons carry one unit instead of two. With this modified helicity we easily explain old and uncover new non-renormalization theorems for theories including gravitons. We provide complete results for the one-loop gravitational renormalization of a generic minimally coupled gauge theory with scalars and fermions and all orders in $M_{Pl}$, as well as for the renormalization of dimension-six operators including at least one graviton, all up to four external particles.

hep-th↗

arXiv2021

The QCD Axion at Finite Density

We show how the properties of the QCD axion change in systems at finite baryonic density, such as neutron stars. At nuclear saturation densities, where corrections can be reliably computed, we find a mild reduction of the axion mass and up to an order of magnitude enhancement in the model-independent axion coupling to neutrons. At moderately higher densities, if realized, meson (kaon) condensation can trigger axion condensation. We also study the axion potential at asymptotically large densities, where the color-superconducting phase of QCD potentially leads to axion condensation, and the mass of the axion is generically several orders of magnitude smaller than in vacuum due to the suppressed instantons. Several phenomenological consequences of the axion being sourced by neutron stars are discussed, such as its contribution to their total mass, the presence of an axionic brane, or axion-photon conversion in the magnetosphere.

hep-ph↗

arXiv2021

Runaway Relaxion from Finite Density

Finite density effects can destabilize the metastable vacua in relaxion models. Focusing on stars as nucleation seeds, we derive the conditions that lead to the formation and runaway of a relaxion bubble of a lower energy minimum than in vacuum. The resulting late-time phase transition in the universe allows us to set new constraints on the parameter space of relaxion models. We also find that similar instabilities can be triggered by the large electromagnetic fields around rotating neutron stars.

hep-ph↗

arXiv2021

Density Induced Vacuum Instability

We consider matter density effects in theories with a false ground state. Large and dense systems, such as stars, can destabilize a metastable minimum and allow for the formation of bubbles of the true minimum. We derive the conditions under which these bubbles form, as well as the conditions under which they either remain confined to the dense region or escape to infinity. The latter case leads to a phase transition in the universe at star formation. We explore the phenomenological consequences of such seeded phase transitions.

hep-ph↗