arXiv subjects

Daniel Schmitt

Publications and source records attributed to Daniel Schmitt.

13 recordsLinked to original sources

arXiv2026

Theoretical uncertainties in reconstructing model parameters with gravitational waves from supercooled phase transitions

Future interferometers may detect a gravitational-wave (GW) signal from a cosmological first-order phase transition. Reconstructing the underlying particle-physics model from such a signal requires theoretical control over the map from microphysics to the spectrum. For classically scale-invariant extensions of the Standard Model, which generically predict strongly supercooled transitions and strong GW signals, this map depends sensitively on the treatment of quantum and thermal corrections to the nucleation rate. Taking the classically conformal ${\rm U}(1)_X$ model as representative of this class, we scan its parameter space and compare two resummation schemes. The first is a high-temperature effective field theory, matched at two-loop level and including next-to-leading-order corrections to the bounce action, with the nucleation-rate prefactor given by the full one-loop functional determinants. The second is a commonly employed daisy-resummed effective potential, with the prefactor estimated on dimensional grounds. Reconstructing the fundamental model parameters through a Fisher-matrix analysis of injected GW signals at LISA, we find that the daisy-resummation scheme is strongly disfavored, as its theoretical error dominates over the reconstruction uncertainty.

hep-ph↗

arXiv2026

Audible Axion Magnetogenesis: Linking Intergalactic Magnetic Fields and Gravitational Waves

Identifying dark matter candidates that simultaneously generate multiple observable cosmological signatures is a key goal in connecting particle physics with upcoming observations. Axion-like particles coupled to the Standard Model photon offer a promising framework. In the trapped misalignment mechanism, the onset of axion oscillations is delayed, inducing a period of supercooling in the early Universe. This can lead to exponential production of photon quanta via a tachyonic instability, generating observable gravitational wave signatures. Simultaneously, reheating of the Standard Model plasma produces strong, helical magnetic fields on intergalactic scales. The parameter space most promising for gravitational wave detection yields magnetic field strengths that exceed lower bounds from blazar observations.

hep-ph↗

arXiv2025

Trapped and Unstable: Axion-like particle fragmentation at finite temperature

We investigate the emergence of a resonant behavior in axion-trapped misalignment models featuring finite-temperature potential barriers. As the temperature decreases and the field is released from its trapped configuration, inhomogeneities are exponentially amplified through an instability in their equation of motion, leading to the fragmentation of the axion field. We show that this process constitutes a novel source of gravitational waves (GWs), analogous to those generated in zero-temperature axion fragmentation, but with distinct characteristics. We quantify the resulting GW spectrum, identifying the peak frequency and amplitude associated with the inhomogeneous axion dynamics. Our results indicate that the GW signal can be enhanced by up to two orders of magnitude compared to the standard fragmentation scenario, while exhibiting a markedly different spectral shape. The parameter space featuring both strong GW signals and reproducing the correct dark matter abundance is, however, limited.

hep-ph↗

arXiv2025

Thermodynamical uncertainties for primordial black holes from cosmological phase transitions

Strongly supercooled first-order phase transitions have been proposed as a primordial black hole (PBH) production mechanism. While previous works rely on simplified models with limited thermodynamic precision, we stress that reliable theoretical PBH predictions require precise nucleation dynamics within realistic extensions of the Standard Model. By employing high-temperature dimensional reduction and computing the one-loop fluctuation determinants, we provide a state-of-the-art thermodynamic analysis and obtain an universal lower bound on the transition timescale, $\beta/H_* \simeq 5$. Then, we estimate the corresponding PBH abundance for classically conformal gauge-Higgs theories. Accounting for constraints from successful percolation and QCD chiral symmetry breaking, the parameter space where PBHs are viable dark matter candidates is severely limited.

hep-ph↗

arXiv2025

Impact of theoretical uncertainties on model parameter reconstruction from GW signals sourced by cosmological phase transitions

Different computational techniques for cosmological phase transition parameters can impact the Gravitational Wave (GW) spectra predicted in a given particle physics model. To scrutinize the importance of this effect, we perform large-scale parameter scans of the dynamical real-singlet extended Standard Model using three perturbative approximations for the effective potential: the $\overline{\rm MS}$ and on-shell schemes at leading order, and three-dimensional thermal effective theory (3D EFT) at next-to-leading order. While predictions of GW amplitudes are typically unreliable in the absence of higher-order corrections, we show that the reconstructed model parameter spaces are robust up to a few percent in uncertainty. While 3D EFT is accurate from one loop order, theoretical uncertainties of reconstructed model parameters, using four-dimensional standard techniques, remain dominant over the experimental ones even for signals merely strong enough to claim a detection by LISA.

hep-ph↗

arXiv2025

Supercooled Audible Axions

In the audible axion mechanism, axion-like particles source primordial gravitational waves via their coupling to a dark Abelian gauge field. The original setup, however, relies on a large axion decay constant and coupling to produce sizable signals. In this article, we show that delaying the onset of axion oscillations opens up the testable parameter space and reduces the required coupling to $\alpha \gtrsim 1$. Furthermore, we investigate the emission of gravitational waves via the axion coupling to the Standard Model photon in the presence of Schwinger pair production, generating a strong signal in the $\mu$Hz or ultra-high frequency range. Cosmological constraints and gravitational wave projections are provided for both scenarios.

hep-ph↗

arXiv2025

QCD-sourced tachyonic phase transition in a supercooled Universe

We propose a novel gravitational wave production mechanism in the context of quasi-conformal Standard Model extensions, which provide a way to dynamically generate the electroweak scale. In these models, the cosmic thermal history is modified by a substantial period of thermal inflation, potentially supercooling the Universe below the QCD scale. The exit from supercooling is typically realized through a strong, first-order phase transition. By employing the classically conformal $U(1)_{\tiny\rm B-L}$ model as a representative example, we show that a large parameter space exists where bubble percolation is inefficient. In this case, the top quark condensate triggers a tachyonic phase transition driven by classical rolling of the new scalar field towards the true vacuum. As the field crosses a region where its effective mass is negative, long-wavelength scalar field fluctuations are exponentially amplified, preheating the supercooled Universe. We study the dynamics of this scenario and estimate the peak of the associated gravitational wave signal, which is detectable by future observatories in almost the entire available parameter space.

hep-ph↗

arXiv2024

Binary systems in massive scalar-tensor theories: Next-to-leading order gravitational wave phase from effective field theory

Neutron star binaries and their associated gravitational wave signal facilitate precision tests of General Relativity. Any deviation of the detected gravitational waveform from General Relativity would therefore be a smoking gun signature of new physics, in the form of additional forces, dark matter particles, or extra gravitational degrees of freedom. To be able to probe new theories, precise knowledge of the expected waveform is required. In our work, we consider a generic setup by augmenting General Relativity with an additional, massive scalar field. We then compute the inspiral dynamics of a binary system, for circular orbits, by employing an effective field theoretical approach, while giving a detailed introduction to the computational framework. Finally, we derive the modified TaylorF2 phase of the gravitational wave signal at next-to-leading order in the post-Newtonian expansion, and leading order in the parameters of the scalar sector, such as the scalar charge. As a consequence of our model-agnostic approach, our results are readily adaptable to a plethora of new physics scenarios, including modified gravity theories and scalar dark matter models.

gr-qc↗

arXiv2023

Supercool exit: Gravitational waves from QCD-triggered conformal symmetry breaking

Classically conformal Standard Model extensions predict an intriguing thermal history of the early universe. In contrast to the common paradigm, the onset of the electroweak phase transition can be significantly delayed while the universe undergoes a period of thermal inflation. Then, a first-order chiral phase transition could not only trigger electroweak symmetry breaking but also initiate the exit from supercooling. To study the dynamics of this scenario, we focus on low-energy quark-based QCD effective models that exhibit a first-order transition. While a large amount of latent heat is naturally involved if thermal inflation ends, we find that a supercooling period prior to the QCD scale considerably enhances the timescale of the transition. This enhancement implies great observational prospects at future gravitational wave observatories. Our results are readily applicable to a wide class of scale-invariant SM extensions, as well as strongly coupled dark sectors.

hep-ph↗

arXiv2023

TicTacToes: Assessing Toe Movements as an Input Modality

From carrying grocery bags to holding onto handles on the bus, there are a variety of situations where one or both hands are busy, hindering the vision of ubiquitous interaction with technology. Voice commands, as a popular hands-free alternative, struggle with ambient noise and privacy issues. As an alternative approach, research explored movements of various body parts (e.g., head, arms) as input modalities, with foot-based techniques proving particularly suitable for hands-free interaction. Whereas previous research only considered the movement of the foot as a whole, in this work, we argue that our toes offer further degrees of freedom that can be leveraged for interaction. To explore the viability of toe-based interaction, we contribute the results of a controlled experiment with 18 participants assessing the impact of five factors on the accuracy, efficiency and user experience of such interfaces. Based on the findings, we provide design recommendations for future toe-based interfaces.

cs.HC↗

arXiv2022

Directed Acoustic Assembly in 3D

The creation of whole 3D objects in one shot is an ultimate goal for rapid prototyping, most notably biofabrication, where conventional methods are typically slow and apply mechanical or chemical stress on biological cells. Here, we demonstrate one-step assembly of matter to form compact 3D shapes using acoustic forces, which is enabled by the superposition of multiple holographic fields. The technique is contactless and shown to work with solid microparticles, hydrogel beads and biological cells inside standard labware. The structures can be fixed via gelation of the surrounding medium. In contrast to previous work, this approach handles matter with positive acoustic contrast and does not require opposing waves, supporting surfaces or scaffolds. We envision promising applications in tissue engineering and additive manufacturing.

cond-mat.soft↗

arXiv2022

Audible Axions with a Booster: Stochastic Gravitational Waves from Rotating ALPs

Gravitational waves provide a novel way to probe axions or axion-like particles coupled to a dark photon field, even in the absence of couplings to Standard Model particles. In the conventional misalignment mechanism, the generation of an observable stochastic gravitational wave background, however, requires large axion decay constants. We here investigate the gravitational wave signal generated within the kinetic misalignment scenario, where the axion is assumed to have a large initial velocity. Its kinetic energy then provides a sufficiently high energy budget to generate a detectable gravitational wave signal also at lower values of the decay constant. We obtain an analytic estimate as well as perform numerical simulations of the corresponding gravitational wave signal, and evaluate its detectability at current and future gravitational wave observatories. We further present the corresponding projected constraints on the parameter space of the model, along with the parameter regions in which the dark photon or axion constitute dark matter, or in which the baryon asymmetry of the Universe is generated via the axiogenesis mechanism. Finally we compute the GW production from the fragmentation of rotating axions, which is however difficult to observe experimentally.

hep-ph↗

arXiv2018

Proceedings of eNTERFACE 2015 Workshop on Intelligent Interfaces

The 11th Summer Workshop on Multimodal Interfaces eNTERFACE 2015 was hosted by the Numediart Institute of Creative Technologies of the University of Mons from August 10th to September 2015. During the four weeks, students and researchers from all over the world came together in the Numediart Institute of the University of Mons to work on eight selected projects structured around intelligent interfaces. Eight projects were selected and their reports are shown here.

cs.HC↗