arXiv subjects

Erik W. Lentz

Publications and source records attributed to Erik W. Lentz.

14 recordsLinked to original sources

arXiv2026

Developing Centimeter-scale-cavity Arrays for Axion Dark Matter Detection in the 100 Micro-electron-volt Range

The cavity haloscope technique has been the most successful approach to date in searching for axion dark matter, owing to a confluence of factors at the GHz scale including the macroscopic size of the axion-to-photon converting cavity volume, the sophistication of present radio-frequency/microwave technologies including quantum amplifiers, and the location of the quantum limit temperature. These factors scale in a disadvantageous way overall as searches move up the axion mass/frequency scale, with the quantum limit noise temperature scaling linearly with frequency $T_{\text{SQL}} \sim f$, the effective single cavity volume scaling as the inverse frequency cubed $C V \sim f^{-3}$, and the axion-coupled cavity mode quality factor shrinking as $Q \sim f^{-2/3}$ for copper cavities, necessitating the search for remedies. One approach is to make up the loss in volume using an array of efficiently packed matched cavities coordinated in space and time to act as a single axion-to-photon converting array. This paper presents PNNL's progress in developing technologies for cavity array axion haloscope in the $m_a \sim 100$ micro-eV mass range including the design of moderate scale cm-diameter cavities and their fabrication process using electric discharge machining, the development of mode tuning mechanisms towards a re-entrant style combination tuning rod and coupler, mode matching, and RF readout. The result is the first demonstration of a tunable array of matched cavities with axion-coupling modes in the $f_0 \in [22.88,22.93]$ GHz ($94.62-94.83$ micro-eV) range. Prospects for future larger arrays leading to viable axion DM searches of this type in this mass range are discussed.

hep-ex↗

arXiv2025

Signatures from Non-classical Features of Axion Dark Matter in Cavity Haloscopes

I present in this article how non-classical features in the local axion dark matter state may imprint on cavity haloscopes. Example signatures from squeezed and pair-entangled DM states are presented and their potential for sensitivity enhancements of experimental searches attuned to these signatures compared to traditional classical field signatures are discussed.

hep-ph↗

arXiv2024

Motivating Emissions from Positive Energy Warp Bubbles

Recent research has proposed that advanced propulsion mechanisms such as warp drives are more physically feasible than previously thought, using positive energy sources potentially sourced by known classical physics. Motivated by this, we hypothesize that an advanced inter-planetary or interstellar civilization using warp drives at sub-luminal or super-luminal speeds will broadcast detectable emissions of their travels. These technosignatures would be of significant astronomical, physical, and technological interest. This paper seeks to motivate signatures from warp drive emissions due to intrinsic and extrinsic processes across several messenger types (electromagnetic, particle, and gravitational) and propose a research program to simulate such emissions in sufficient detail to search for their signatures through coordinated analyses across multiple observatories.

astro-ph.IM↗

arXiv2022

Snowmass Theory Frontier: Astrophysics and Cosmology

We summarize progress made in theoretical astrophysics and cosmology over the past decade and areas of interest for the coming decade. This Report is prepared as the TF09 "Astrophysics and Cosmology" topical group summary for the Theory Frontier as part of the Snowmass 2021 process.

hep-ph↗

arXiv2021

Hyper-Fast Positive Energy Warp Drives

Solitons in space-time capable of transporting time-like observers at superluminal speeds have long been tied to violations of the weak, strong, and dominant energy conditions of general relativity. This trend was recently broken by a new approach that identified soliton solutions capable of superluminal travel while being sourced by purely positive energy densities. This is the first example of hyper-fast solitons satisfying the weak energy condition, reopening the discussion of superluminal mechanisms rooted in conventional physics. This article summarizes the recent finding and its context in the literature. Remaining challenges to autonomous superluminal travel, such as the dominant energy condition, horizons, and the identification of a creation mechanism are also discussed.

gr-qc↗

arXiv2021

New insights into the formation and growth of boson stars in dark matter halos

This work studies the formation and growth of boson stars and their surrounding miniclusters by gravitational condensation using non-linear dynamical numerical methods. Fully dynamical attractive and repulsive self-interactions are also considered for the first time. In the case of pure gravity, we numerically prove that the growth of boson stars inside halos slows down and saturates as has been previously conjectured, and detail its conditions. Self-interactions are included using the Gross-Pitaevskii-Poisson equations. We find that in the case of strong attractive self-interactions the boson stars can become unstable and collapse, in agreement with previous stationary computations. At even stronger coupling, the condensate fragments. Repulsive self-interactions, as expected, promote boson star formation, and lead to solutions with larger radii.

astro-ph.CO↗

arXiv2020

Breaking the Warp Barrier: Hyper-Fast Solitons in Einstein-Maxwell-Plasma Theory

Solitons in space--time capable of transporting time-like observers at superluminal speeds have long been tied to violations of the weak, strong, and dominant energy conditions of general relativity. The negative-energy sources required for these solitons must be created through energy-intensive uncertainty principle processes as no such classical source is known in particle physics. This paper overcomes this barrier by constructing a class of soliton solutions that are capable of superluminal motion and sourced by purely positive energy densities. The solitons are also shown to be capable of being sourced from the stress-energy of a conducting plasma and classical electromagnetic fields. This is the first example of hyper-fast solitons resulting from known and familiar sources, reopening the discussion of superluminal mechanisms rooted in conventional physics.

gr-qc↗

arXiv2020

Mixed State Dynamics with Non-Local Interactions

The evolution of degenerate matter out of equilibrium is a topic of interest in fields such as condensed matter, nuclear and atomic physics, and increasingly cosmology, including inflaton physics prior to reheating. This follow-up paper extends the recent paper on the super-de Broglie dynamics of pure condensates of non-relativistic identical particles subject to non-local two-body interactions to the dynamics of mixed states. It is found that the two-body correlation function plays an increasingly dynamical role in these systems, driving the development of condensates and distributed phases alike. Examples of distribution and correlation evolution are presented, including instances of collapse, bound and unbound states, and phonons in the bulk. Potential applications are also discussed.

astro-ph.CO↗

arXiv2019

Exotic Behaviors of Space-time in Einstein-Maxwell Theory

This paper examines the structure of electric fields and space-times created by extended finite distributions of irrotational static and spherically-symmetric charge. The resulting electric fields are found to source features in space-time commonly associated with the presence of fields with locally positive and negative mass densities, with the sign of the mass corresponding to the sign of the electric field gradient. The conditions detailing these behaviors are discussed. The effects of these structures on trajectories of time-like geodesics and the volume form are also presented.

gr-qc↗

arXiv2019

A Proposal to Detect Dark Matter Using Axionic Topological Antiferromagnets

Antiferromagnetically doped topological insulators (A-TI) are among the candidates to host dynamical axion fields and axion-polaritons; weakly interacting quasiparticles that are analogous to the dark axion, a long sought after candidate dark matter particle. Here we demonstrate that using the axion quasiparticle antiferromagnetic resonance in A-TI's in conjunction with low-noise methods of detecting THz photons presents a viable route to detect axion dark matter with mass 0.7 to 3.5 meV, a range currently inaccessible to other dark matter detection experiments and proposals. The benefits of this method at high frequency are the tunability of the resonance with applied magnetic field, and the use of A-TI samples with volumes much larger than 1 mm$^3$.

hep-ph↗

arXiv2019

Axion Structure Formation II: The Wrath of Collapse

The first paper in this series showed that QCD axion dark matter, as a highly-correlated Bose fluid, contains extra-classical physics on cosmological scales. The nature of the derived extra-classical physics is exchange-correlation interactions induced by the constraints of symmetric particle exchange and inter-axion correlations from self-gravitation. The paper also showed that the impact of extra-classical physics on early structure formation is marginal, as the exchange-correlation interaction is inherently non-linear. This paper continues the study of axion structure formation into the non-linear regime by now considering the case of full collapse and virialization. The N-body method is chosen to solve the collapse problem, and its algorithms are derived for a condensed Bose fluid. Simulations of isolated gravitational collapse are performed for both Bose and cold dark matter fluids using a prototype N-body code. Unique Bose structures are found to survive even the most violent collapses. Bose post-collapse features include dynamical changes to global structures, creation of new broad substructures, violations of classical binding energy conditions, and new fine structures. Effective models of the novel structures are constructed and possibilities for their discovery are discussed.

astro-ph.CO↗

arXiv2018

Axion Structure Formation I: The Co-motion Picture

Axions as dark matter is an increasingly important subject in astrophysics and cosmology. Experimental and observational searches are mounting across the mass spectrum of axion-like particles, many of which require detailed knowledge of axion structure over a wide range of scales. Current understanding of axion structures is far from complete, however, due largely to controversy in modeling the candidate's highly-degenerate state. The series Axion Structure Formation seeks to develop a consistent model of QCD axion dark matter dynamics that follows their highly-degenerate nature to the present using novel modeling techniques and sophisticated simulations. This inaugural paper presents the problem of describing many non-relativistic axions with minimal degrees of freedom and constructs a theory of axion infall for the limit of complete condensation. The derived model is shown to contain axion-specific dynamics not unlike the exchange-correlation influences experienced by identical fermions. Perturbative calculations are performed to explore the potential for imprints in early universe structures.

astro-ph.CO↗

arXiv2017

A New Signal Model for Axion Cavity Searches from N-Body Simulations

Signal estimates for direct axion dark matter searches have used the isothermal sphere halo model for the last several decades. While insightful, the isothermal model does not capture effects from a halo's infall history nor the influence of baryonic matter, which has been shown to significantly influence a halo's inner structure. The high resolution of cavity axion detectors can make use of modern cosmological structure-formation simulations, which begin from realistic initial conditions, incorporate a wide range of baryonic physics, and are capable of resolving detailed structure. This letter uses a state-of-the-art cosmological N-body+Smoothed-Particle Hydrodynamics simulation to develop an improved signal model for axion cavity searches. Signal shapes from a class of galaxies encompassing the Milky Way are found to depart significantly from the isothermal sphere. A new signal model for axion detectors is proposed and projected sensitivity bounds on the Axion Dark Matter eXperiment data are presented.

astro-ph.GA↗

arXiv2016

Effects of Angular Momentum on Halo Profiles

The near universality of DM halo density profiles provided by N-body simulations has proven to be robust against changes in total mass density, power spectrum, and some forms of initial velocity dispersion. In this letter we study the effects of coherently spinning up an isolated DM-only progenitor on halo structure. Halos with spins within several standard deviations of the simulated mean ($λ\lesssim 0.20$) produce profiles with negligible deviations from the universal form. Only when the spin becomes quite large ($λ\gtrsim 0.20$) do departures become evident. The angular momentum distribution also exhibits a near universal form, which is also independent of halo spin up to $λ\lesssim 0.20$. A correlation between these epidemic profiles and the presence of a strong bar in the virialized halo is also observed. These bar structures bear resemblance to the radial orbit instability in the rotationless limit.

astro-ph.GA↗