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Rodrigo Alonso

Publications and source records attributed to Rodrigo Alonso.

At least 19 recordsLinked to original sources
arXiv2026

Dyonic lattices, $\theta$-angles and axions in the Standard Model

We investigate the implications of the Witten effect in the Standard Model with a general global gauge group structure and determine the values of the three $\theta$-parameters that lead to distinct families of allowed spectra of dyons. We construct and classify the corresponding dyonic charge lattices consistent with the Standard Model gauge structure. This approach enables us to re-derive the known global-group--dependent periodicities of the $\theta$ angles and to determine all CP-invariant points in $\theta$-space. The electromagnetic subgroup $U(1)_{\mathrm{em}}$ is shown to arise \emph{prior} to electroweak symmetry breaking by factoring out the effect of the anomalous $B+L$ transformations, which reduces the physical $\theta$-parameter space from a three-torus to a two-torus. Our phenomenological conclusions include an observation that a discovery of a $U(1)_{\mathrm{em}}$ monopole carrying non-zero electric charge would determine the last remaining unknown parameter of the Standard Model. Lastly we study how $\theta$-space shapes axion physics with emphasis on the axion-photon coupling and show that a single axion is insufficient to render the Standard Model vacuum fully CP invariant.

hep-ph↗
arXiv2025

The Potential of HEFT and the scale of New Physics

We employ a geometric framework to compute the leading high-energy behaviour of tree-level scattering amplitudes in theories containing $N$ Nambu-Goldstone bosons and a single Higgs-like scalar with an arbitrary potential $V$. Using these methods, we obtain closed-form expressions for the leading contribution to the full infinite set of tree amplitudes involving any number of Goldstone and Higgs-like external states. These results are then used to derive total cross sections, decay rates, and perturbative unitarity bounds. We then apply our general formalism to the Standard Model scalar sector using the equivalence theorem, working in the regime of small field-space curvature, and use it to characterise the relation between Higgs Effective Field Theory (HEFT) and the Standard Model Effective Field Theory (SMEFT). We analyse three representative classes of models. Two reproduce previously known behaviours, while the third, based on a dilaton effective theory, exhibits a noteworthy feature within the HEFT framework: a smooth decoupling limit that connects HEFT directly to the Standard Model without passing through a SMEFT regime, providing a possible backdoor to the Standard Model.

hep-ph↗
arXiv2025

Assessing (H)EFT theory errors by pitting EoM against Field Redefinitions

Truncations of effective field theory expansions are technically necessary but inherently intertwined with the redundancies of general field redefinitions. This can be viewed as a juxtaposition of power-counting and theoretical uncertainties, which seek to estimate neglected higher-dimensional interactions through approaches based on community consensus. One can then understand the invariance of physics under field redefinitions as a data-informed validation of different power-counting schemes, or as a means of assigning theoretical errors in comparison with algebraic, equation of motion-based replacements. Such an approach generalises widely accepted procedures for estimating theoretical uncertainties within the SM to non-renormalisable interactions. We perform a case study for a representative example in Higgs Effective Field theory, focusing on universal Higgs properties tensioned against process-dependent sensitivity expectations.

hep-ph↗
arXiv2025

Sensitivity of $W$-boson measurements to low-mass right-handed neutrinos

A low-mass right-handed neutrino could interact with electroweak bosons via mixing, a mediator particle, or loop corrections. Using an effective field theory, we determine constraints on these interactions from $W$-boson measurements at hadron colliders. Due to the difference in the initial states at the Tevatron and the LHC, $W$-boson decays to a right-handed neutrino would artificially increase the mass measured at the Tevatron while only affecting the difference between $W^+$ and $W^-$ mass measurements at the LHC. Measurements from CDF and the LHC are used to infer the corresponding parameter values, which are found to be inconsistent between the two. The LHC experiments can improve sensitivity to these interactions by measuring the cosine of the helicity angle using $W$ bosons produced with transverse momentum above $\approx 50$ GeV.

hep-ph↗
arXiv2025

Charge quantisation, monopoles and emergent symmetry in the Standard Model and its embeddings

This work studies the connection of the global properties of the SM gauge group to 1-form discrete symmetries, the possible non-Abelian embeddings of the SM group, and electric and magnetic charge quantisation. Building on previous work, we introduce indexes to characterise the group choices, connect the concept of compositeness degree to emergent electric 1-form symmetry, introduce a new model to fill in the $p=1$ gap, and analyse the magnetic spectrum while connecting its UV and IR realisations.

hep-ph↗
arXiv2025

A particle physicist lacing their shoes

This letter presents the solution to a counting problem, to the best of our knowledge not known in full generality, which can be mapped to both (i) ways to lace a $N$-holes-per-side shoe with $\ell$ shoestrings and (ii) a sum over the indexes of $2N$-tensors made of symmetric 2-tensors. The coefficients that answer this question are then connected to spin $J=N$ boson exchange amplitudes and perturbative unitarity constraints, deriving relations with Legendre polynomials and sum rules.

hep-th↗
arXiv2025

Active energy harvesting and work transduction by hair-cell bundles in bullfrog's inner ear

Hair cells actively drive oscillations of their mechanosensitive organelles--the hair bundles that enable hearing and balance sensing in vertebrates. Why and how some hair cells expend energy by sustaining this oscillatory motion in order to fulfill their function as signal sensors and others--as amplifiers, remains unknown. We develop a stochastic thermodynamic theory to describe energy flows in a periodically-driven hair bundle. Our analysis of thermodynamic fluxes associated with hair bundles' motion and external sinusoidal stimulus reveals that these organelles operate as thermodynamic work-to-work machines under different operational modes. One operational mode transduces the signal's power into the cell, whereas another allows the external stimulus to harvest the energy supplied by the cell. These two regimes might represent thermodynamic signatures of signal sensing and amplification respectively. In addition to work transduction and energy harvesting, our model also substantiates the capability of hair-cell bundles to operate as heaters and, at the expense of external driving, as active feedback refrigerators. We quantify the performance and robustness of the work-to-work conversion by hair bundles, whose efficiency in some conditions exceeds 80 % of the applied power.

cond-mat.stat-mech↗
arXiv2024

Counting and building operators in theories with hidden symmetries and application to HEFT

Identifying a full basis of operators to a given order is key to the generality of Effective Field Theory (EFT) and is by now a problem of known solution in terms of the Hilbert series. The present work is concerned with hidden symmetry in general and Higgs EFT in particular and {\it(i)} connects the counting formula presented in [1] in the CCWZ formulation with the linear frame and makes this connection explicit in HEFT {\it (ii)} outlines the differences in perturbation theory in each frame {\it (iii)} presents a new counting formula with measure in the full $SU(3)\times SU(2)\times U(1)$ group for HEFT and {\it (iv)} provides a Mathematica code that produces the number of operators at the user-specified order in HEFT.

hep-ph↗
arXiv2024

Fractional-charge hadrons and leptons to tell the Standard Model group apart

The gauge group of strong and electroweak interactions in Nature could be any of the four that share the same Lie algebra, $SU(3)_c\times SU(2)_L\times U(1)_Y/Z_p\equiv G_p$ with $Z_p=\left\{Z_6,Z_3,Z_2,Z_1\right\}$. Each of these cases allows in its spectrum for the matter fields of the SM but also for new distinctive representations, e.g. under the assumption that $q_L$ possesses the minimum possible hypercharge in Nature, $G_p$ allows for particles with a multiple of $p\,e/6$ for electric charge. This letter discusses how these new possibilities in the spectrum could be used to tell the SM group apart.

hep-ph↗
arXiv2023

Walls, bubbles and doom -- the cosmology of HEFT

As experiment charts new territory at the electroweak scale, the enterprise to characterise all possible theories becomes all the more necessary. In the absence of new particles, this ambitious enterprise is attainable and has led to the Higgs Effective Field Theory (HEFT) as the most general characterising framework, containing the Standard Model Effective Field Theory (SMEFT) as a subspace. The characterisation of this theory space led to the dichotomy SMEFT vs. HEFT\SMEFT as the two possible realisations of symmetry breaking. The criterion to distinguish these two possibilities is non-local in field space, and phenomena which explore field space beyond the neighbourhood of the vacuum manifold are in a singular position to tell them apart. Cosmology allows for such phenomena, and this work focuses on HEFT\SMEFT, the less explored of the two options, to find that first order phase transitions with detectable gravitational wave remnants, domain wall formation and vacuum decay in the far, far distant future can take place and single out HEFT\SMEFT. Results in cosmology are put against LHC constraints, and the potential of future ground- and space-based experiments to cover parameter space is discussed.

hep-ph↗
arXiv2023

A primer on Higgs Effective Field Theory with Geometry

These lecture notes, prepared for the 2022 QUC summer school at KIAS, provide an introduction to Higgs Effective Field Theory and the use of field geometry in Quantum Field Theory. While not sounding the depths of any of these topics, we will cover and give a sense of the inner workings of: the action for Goldstone bosons, the independence of scattering amplitudes from field parametrisations, linear vs non-linear realizations --their `geography' and experimental prospects to tell them apart--, ultra-violet completions and the LSZ formula for fields in curved space.

hep-ph↗
arXiv2022

On the effective action for scalars in a general manifold to any loop order

Functional methods and a derivative expansion are employed for laying out a procedure to compute the effective action to any loop order, for scalar fields parametrising an arbitrary Riemannian manifold, while maintaining explicit field-space covariance. In this process, the geometric generalization of the LSZ reduction formula is presented. These results are of use in the characterization of effective field theories for electroweak symmetry breaking and extend a geometric perspective in field space beyond one loop.

hep-th↗
arXiv2021

On the road(s) to the Standard Model

Experimental measurements point at the Standard Model (SM) as the theory of electroweak symmetry breaking, but as we close in on our characterization the question arises of what limits in theory space lead to the SM. The class of theories with this property cannot be ruled out, only constrained to an ever smaller neighbourhood of the SM. In contrast, which class of theories do not posses this limit and can therefore potentially be ruled out experimentally? In this work we study both classes and find evidence to support the Standard Model Effective field theory being the single road to the Standard Model, theories that fall outside this class keeping a `minimum distance' from the SM characterized by a cut-off of at most $ 4\pi v/g_{\rm SM}$.

hep-ph↗
arXiv2021

Prospects for direct CP tests of $hqq$ interactions

We study the prospects for probing the CP structure of $hqq$ interactions using the decays of the lightest baryon $\Lambda_q$ formed in the quark's hadronization. The low yields of reconstructible events make it unlikely for tests to be performed with the next generation of colliders. In $h\to b\bar b\to \Lambda_b \bar\Lambda_b$ decays a CP-sensitive distribution could be measured with a high-luminosity $e^+ e^-$ collider, while in both $h\to b\bar b\to \Lambda_b \bar\Lambda_b$ and $h\to c\bar c\to \Lambda_c \bar\Lambda_c$ decays such a distribution could be measured with a very high luminosity $\mu^+ \mu^-$ collider. However, we find that only the $\mu^+ \mu^-$ collider can produce enough $h\to b\bar b\to \Lambda_b \bar\Lambda_b$ decays to probe a physical CP asymmetry in the $hbb$ vertex.

hep-ph↗
arXiv2020

Kick-alignment: matter asymmetry sourced dark matter

We investigate the possibility that the dark matter abundance is sourced by the baryon/lepton asymmetry of the early Universe. It turns out that a Goldstone field of a local classically preserved symmetry in the Standard Model experiences a kick during a period of baryon/lepton number generation. This mechanism can be regarded as dynamical generation of initial conditions for misalignment yet the prediction for relic abundance presents an inverse dependence on the coupling in parallel with freeze-in vs freeze-out. We explore two realizations of this mechanism and show that in conjunction with leptogenesis, it is possible to identify a viable promising region of parameter space for dark matter production with mass 10 MeV - 1 GeV and decay constant f in the range of $10^{10} - 10^{12}$ GeV.

hep-ph↗
arXiv2019

Covariant derivative expansion for the renormalization of gravity

The one loop UV divergences of Hilbert-Einstein gravity with a cosmological constant and spin 0, 1/2 and 1 matter are computed making use of a covariant derivative expansion and functional methods. For this purpose the transformation that yields the covariant derivative is extended to include a dynamical metric and the expansion in the fields themselves is made covariant which is relevant for the effective action due to the non-linear character of gravity

hep-ph↗
arXiv2019

On amplitudes, resonances and the ultraviolet completion of gravity

This letter constructs, making use of the on-shell spinor-helicity formalism, a possible ultraviolet completion of gravity following a "bottom-up" approach. The assumptions of locality, unitarity and causality i) require an infinite tower of resonances with increasing spin and quantized mass, ii) introduce a duality relation among crossed scattering channels, and iii) dress all gravitational amplitudes in the Standard Model with a form factor that closely resembles either the Veneziano or the Virasoro-Shapiro amplitude in string theory. As a consequence of unitarity, the theory predicts leading order deviations from General Relativity in the coupling of gravity to fermions that could be explained if space-time has torsion in addition to curvature.

hep-ph↗