arXiv subjects

Christopher B. Verhaaren

Publications and source records attributed to Christopher B. Verhaaren.

At least 19 recordsLinked to original sources

arXiv2026

Understanding the Quantized Angular Momentum of Rotating Q-balls

Non-topological solitons, such as Q-balls, may contribute to the cosmological dark matter. The formation and evolution of Q-balls in the early universe requires an understanding of solitons with nonzero angular momentum. We derive (rather than assume) the schematic form of the scalar field configurations that produce rotating Q-balls, which produce their well known quantized angular momentum. This analysis leads to additional insight into the properties of these rotating solitons, including a method for computing their characteristic angular velocity. By considering rotating solitons in two spatial dimensions, we investigate these attributes concretely. We develop analytical approximations for the solitons and their defining quantities. We show that they agree with numerical results and exhibit the general properties of rotating solitons.

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arXiv2025

Review of Neutral Naturalness

The hierarchy between the mass parameter of the Higgs boson and larger mass scales becomes ever more puzzling as experiments explore higher energies. Neutral naturalness is the umbrella term for symmetry-based explanations for these hierarchies whose quark symmetry partners are not charged under the SU(3) color gauge group of the Standard Model. Though the first manifestations of this idea predate the physics runs of the Large Hadron Collider, since the Higgs discovery this paradigm has grown and developed to include a wide variety of concrete realizations with connections to intriguing collider signals. Determining the phenomenology of such models often requires the characterization - typically relying on lattice calculations - of a new confining gauge symmetry. This presents additional motivation to further develop our understanding of nonperturbative field theory as well as to pursue specific lattice studies. The wide range of suggested hidden sectors also produces a variety of dark matter candidates, intersections with astrophysics and cosmology, and ties to neutrinos and flavor. In this review, we orient the reader within both this growing collection of specific models and the physical phenomena they produce. We also survey the often less familiar dynamics of hidden-sector glueballs and quirks. In addition to providing a guide to past efforts, we reveal interesting directions for further study.

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arXiv2025

Extended Color Twin Higgs

We describe a novel variation of the mirror Twin Higgs model in which the color gauge group in both sectors is extended to SU(4$)_c$ and spontaneously broken to SU(3$)_c$ exclusively in the visible sector. Through this process, the mirror $Z_2$ symmetry is spontaneously broken, allowing for a phenomenologically viable electroweak vacuum alignment. This structure produces interesting collider signatures, including heavy vectors and fermions with fractional electric charges. The twin sector, with unbroken SU(4$)_c$, produces interesting cosmological characteristics, such as the possibility to reduce $ΔN_\text{eff}$ and stable spin-0 baryons. The enlarged top quark sector required by the extended color gauge symmetry preserves naturalness, with even less tuning than the original twin Higgs in many circumstances.

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arXiv2025

Visible Collider Signals of Natural Quirks

Though some LHC searches for new physics exceed the TeV scale, there may be discoveries waiting to be made at much lower masses. We outline a simple quirk model, motivated by models that address the hierarchy problem through neutral naturalness, in which new electroweakly charged states with masses as low as 100 GeV have not yet been probed by the LHC. We also describe a novel search strategy which is complementary to current search methods. In particular, we show its potential to discover natural quirks over regions of parameter space that present methods will leave unexplored, even after the LHC's high-luminosity run.

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arXiv2025

Geometrizing the Anomaly

Recently a manifestly gauge invariant formalism for calculating amplitudes in quantum electrodynamics was outlined in which the field strength, rather than the gauge potential, is used as the propagating field. To demonstrate the utility of this formalism we calculate the axial and gauge anomalies explicitly in theories with both electrically and magnetically charged particles. Usually the gauge anomaly is identified as an amplitude that (in certain theories) fails to be gauge invariant, so it seems particularly enlightening to understand it in a manifestly gauge invariant formalism. We find that the three photon amplitude is still anomalous in these same theories because it depends explicitly upon the choice of the Stokes surface needed to couple the field strength to sources, so the gauge anomaly arises from geometric considerations.

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arXiv2024

Schwinger vs Coleman: Magnetic Charge Renormalization

The kinetic mixing of two U(1) gauge theories can result in a massless photon that has perturbative couplings to both electric and magnetic charges. This framework can be used to perturbatively calculate in a quantum field theory with both kinds of charge. Here we re-examine the running of the magnetic charge, where the calculations of Schwinger and Coleman sharply disagree. We calculate the running of both electric and magnetic couplings and show that the disagreement between Schwinger and Coleman is due to an incomplete summation of topological terms in the perturbation series. We present a momentum space prescription for calculating the loop corrections in which the topological terms can be systematically separated for resummation. Somewhat in the spirit of modern amplitude methods we avoid using a vector potential and use the field strength itself, thereby trading gauge redundancy for the geometric redundancy of Stokes surfaces. The resulting running of the couplings demonstrates that Dirac charge quantization is independent of renormalization scale, as Coleman predicted. As a simple application we also bound the parameter space of magnetically charged states through the experimental measurement of the running of electromagnetic coupling.

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arXiv2024

On Q-balls in Anti de Sitter Space

We perform a general analysis of thin-wall Q-balls in AdS space. We provide numeric solutions and highly accurate analytic approximations over much of the parameter space. These analytic solutions show that AdS Q-balls exhibit significant differences from the corresponding flat space solitons. This includes having a maximum radius beyond which the Q-balls are unstable to a new type of state where the Q-ball coexists with a gas of massive particles. The phase transition to this novel state is found to be a zero-temperature third-order transition. This, through the AdS/CFT correspondence, has implications for a scalar condensate in the boundary theory.

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arXiv2024

Slowly rotating Q-balls

Q-balls are non-topological solitons arising in scalar field theories. Solutions for rotating Q-balls (and the related boson stars) have been shown to exist when the angular momentum is equal to an integer multiple of the Q-ball charge $Q$. Here we consider the possibility of classically long-lived metastable rotating Q-balls with small angular momentum, even for large charge, for all scalar theories that support non-rotating Q-balls. This is relevant for rotating extensions of Q-balls and related solitons such as boson stars as it impacts their cosmological phenomenology.

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arXiv2023

Mapping Gauged Q-Balls

Scalar field theories with particular U(1)-symmetric potentials contain non-topological soliton solutions called Q-balls. Promoting the U(1) to a gauge symmetry leads to the more complicated situation of gauged Q-balls. The soliton solutions to the resulting set of nonlinear differential equations have markedly different properties, such as a maximal possible size and charge. Despite these differences, we discover a relation that allows one to extract the properties of gauged Q-balls (such as the radius, charge, and energy) from the more easily obtained properties of global Q-balls. These results provide a new guide to understanding gauged Q-balls as well as providing simple and accurate analytical characterization of the Q-ball properties.

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arXiv2023

Simulating Glueball Production in $N_f = 0$ QCD

In an $SU(N_c)$ gauge theory with zero light quark flavours $N_f = 0$, the only hadronic states that form below the confinement scale are composite gluon states called glueballs. These minimal confining sectors arise in many Hidden Valley extensions of the Standard Model, including scenarios that could hold the solution to the dark matter question and the hierarchy problem. Quantitative study of dark glueball phenomenology requires an understanding of pure glue hadronization, which to date is severely lacking. In this work we show that significant progress can be made by combining a perturbative pure glue parton shower with a self-consistent and physically motivated parameterization of the unknown non-perturbative physics, thanks to the modest hierarchy between the glueball mass and the confinement scale. We make our simulation code available as the public GlueShower package, the first glueball generator for Hidden Valley theories, and perform preliminary studies of several glueball production observables, with theoretical uncertainties that take the full range of possible hadronization scenarios into account. We hope this will enable new studies of dark sector phenomenology that were previously inaccessible.

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arXiv2022

TF08 Snowmass Report: BSM Model Building

We summarize the state of Beyond the Standard Model (BSM) model building in particle physics for Snowmass 2021, focusing mainly on several whitepaper contributions to BSM model building (TF08) and closely related areas.

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arXiv2022

Early-Universe Model Building

Theoretical investigations into the evolution of the early universe are an essential part of particle physics that allow us to identify viable extensions to the Standard Model as well as motivated parameter space that can be probed by various experiments and observations. In this white paper, we review particle physics models of the early universe. First, we outline various models that explain two essential ingredients of the early universe (dark matter and baryon asymmetry) and those that seek to address current observational anomalies. We then discuss dynamics of the early universe in models of neutrino masses, axions, and several solutions to the electroweak hierarchy problem. Finally, we review solutions to naturalness problems of the Standard Model that employ cosmological dynamics.

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arXiv2022

Excited Q-Balls

Complex scalars in U(1)-symmetric potentials can form stable Q-balls, non-topological solitons that correspond to spherical bound-state solutions. If the U(1) charge of the Q-ball is large enough, it can support a tower of unstable radial excitations with increasing energy. Previous analyses of these radial excitations were confined to fixed parameters, leading to excited states with different charges $Q$. In this work, we provide the first characterization of the radial excitations of solitons for fixed charge, providing the physical spectrum for such objects. We also show how to approximately describe these excited states analytically and predict their global properties such as radius, energy, and charge. This enables a complete characterization of the radial spectrum. We also comment on the decay channels of these excited states.

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arXiv2022

Theory, phenomenology, and experimental avenues for dark showers: a Snowmass 2021 report

In this work, we consider the case of a strongly coupled dark/hidden sector, which extends the Standard Model (SM) by adding an additional non-Abelian gauge group. These extensions generally contain matter fields, much like the SM quarks, and gauge fields similar to the SM gluons. We focus on the exploration of such sectors where the dark particles are produced at the LHC through a portal and undergo rapid hadronization within the dark sector before decaying back, at least in part and potentially with sizeable lifetimes, to SM particles, giving a range of possibly spectacular signatures such as emerging or semi-visible jets. Other, non-QCD-like scenarios leading to soft unclustered energy patterns or glueballs are also discussed. After a review of the theory, existing benchmarks and constraints, this work addresses how to build consistent benchmarks from the underlying physical parameters and present new developments for the PYTHIA Hidden Valley module, along with jet substructure studies. Finally, a series of improved search strategies is presented in order to pave the way for a better exploration of the dark showers at the LHC.

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arXiv2022

Twin Quark Dark Matter From Cogenesis

We extend the fraternal twin Higgs scenario to include a novel dark matter candidate as well as a mechanism for generating a matter/antimatter asymmetry in both sectors. A spontaneous breaking of twin color results in quark degrees of freedom that are singlets under the residual twin color group. These twin-color-singlet quarks, along with a subdominant component of twin leptons, constitute the asymmetric dark matter. The asymmetry between matter in antimatter in both sectors is co-generated from the decay of singlet fermions that provide an additional portal between the visible and twin sectors. We discuss the phenomenological aspects of this model, evaluating constraints on the parameter space and highlighting promising discovery channels in future experiments. We briefly discuss how the discovery of signals in multiple experiments may help establish the connection between the mechanisms that address the naturalness, dark matter and matter/antimatter asymmetry puzzles.

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arXiv2021

Proca Q-balls and Q-shells

Non-topological solitons such as Q-balls and Q-shells have been studied for scalar fields invariant under global and gauged U(1) symmetries. We generalize this framework to include a Proca mass for the gauge boson, which can arise either from spontaneous symmetry breaking or via the Stückelberg mechanism. A heavy (light) gauge boson leads to solitons reminiscent of the global (gauged) case, but for intermediate values these Proca solitons exhibit completely novel features such as disconnected regions of viable parameter space and Q-shells with unbounded radius. We provide numerical solutions and excellent analytic approximations for both Proca Q-balls and Q-shells. These allow us to not only demonstrate the novel features numerically, but also understand and predict their origin analytically.

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arXiv2021

Understanding Q-Balls Beyond the Thin-Wall Limit

Complex scalar fields charged under a global U(1) symmetry can admit non-topological soliton configurations called Q-balls which are stable against decay into individual particles or smaller Q-balls. These Q-balls are interesting objects within quantum field theory, but are also of phenomenological interest in several cosmological and astrophysical contexts. The Q-ball profiles are determined by a nonlinear differential equation, and so generally require solution by numerical methods. In this work, we derive analytical approximations for the Q-ball profile in a polynomial potential and obtain simple expressions for the important Q-ball properties of charge, energy, and radius. These results improve significantly on the often-used thin-wall approximation and make it possible to describe Q-balls to excellent precision without having to solve the underlying differential equation.

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arXiv2021

The Ubiquity of Gauged Q-Shells

Non-topological gauged soliton solutions called Q-balls arise in many scalar field theories that are invariant under a U(1) gauge symmetry. The related, but qualitatively distinct, Q-shell solitons have only been shown to exist for special potentials. We investigate gauged solitons in a generic sixth-order polynomial potential (that contains the leading effects of many effective field theories) and show that this potential generically allows for both Q-balls and Q-shells. We argue that Q-shell solutions occur in many, and perhaps all, potentials that have previously only been shown to contain Q-balls. We give simple analytic characterizations of these Q-shell solutions, leading to excellent predictions of their physical properties.

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