arXiv subjects

Darren Forde

Publications and source records attributed to Darren Forde.

11 recordsLinked to original sources

arXiv2025

RelCon: Relative Contrastive Learning for a Motion Foundation Model for Wearable Data

We present RelCon, a novel self-supervised Relative Contrastive learning approach for training a motion foundation model from wearable accelerometry sensors. First, a learnable distance measure is trained to capture motif similarity and domain-specific semantic information such as rotation invariance. Then, the learned distance provides a measurement of semantic similarity between a pair of accelerometry time-series, which we use to train our foundation model to model relative relationships across time and across subjects. The foundation model is trained on 1 billion segments from 87,376 participants, and achieves state-of-the-art performance across multiple downstream tasks, including human activity recognition and gait metric regression. To our knowledge, we are the first to show the generalizability of a foundation model with motion data from wearables across distinct evaluation tasks.

eess.SP↗

arXiv2009

Multi-Parton Scattering Amplitudes via On-Shell Methods

We present an overview of recent developments, based on on-shell techniques, in the calculation of multi-parton scattering amplitudes at one loop that are relevant for phenomenological studies at hadron colliders. These new on-shell methods make efficient use of the physical properties of the hard scattering, such as unitarity and factorization.

hep-ph↗

arXiv2008

Constructing QCD one-loop amplitudes

In the context of constructing one-loop amplitudes using a unitarity bootstrap approach we discuss a general systematic procedure for obtaining the coefficients of the scalar bubble and triangle integral functions of one-loop amplitudes. Coefficients are extracted after examining the behaviour of the cut integrand as the unconstrained parameters of a specifically chosen parametersiation of the cut loop momentum approach infinity.

hep-ph↗

arXiv2007

Direct extraction of one-loop integral coefficients

We present a general procedure for obtaining the coefficients of the scalar bubble and triangle integral functions of one-loop amplitudes. Coefficients are extracted by considering two-particle and triple unitarity cuts of the corresponding bubble and triangle integral functions. After choosing a specific parameterisation of the cut loop momentum we can uniquely identify the coefficients of the desired integral functions simply by examining the behaviour of the cut integrand as the unconstrained parameters of the cut loop momentum approach infinity. In this way we can produce compact forms for scalar integral coefficients. Applications of this method are presented for both QCD and electroweak processes, including an alternative form for the recently computed three-mass triangle coefficient in the six-photon amplitude $A_6(1^-,2^+,3^-,4^+,5^-,6^+)$. The direct nature of this extraction procedure allows for a very straightforward automation of the procedure.

hep-ph↗

arXiv2007

All One-loop Maximally Helicity Violating Gluonic Amplitudes in QCD

We use on-shell recursion relations to compute analytically the one-loop corrections to maximally-helicity-violating n-gluon amplitudes in QCD. The cut-containing parts have been computed previously; our work supplies the remaining rational parts for these amplitudes, which contain two gluons of negative helicity and the rest positive, in an arbitrary color ordering. We also present formulae specific to the six-gluon cases, with helicities (- + - + + +) and (- + + - + +), as well as numerical results for six, seven, and eight gluons. Our construction of the n-gluon amplitudes illustrates the relatively modest growth in complexity of the on-shell-recursive calculation as the number of external legs increases. These amplitudes add to the growing body of one-loop amplitudes known for all n, which are useful for studies of general properties of amplitudes, including their twistor-space structure.

hep-ph↗

arXiv2006

On-Shell Unitarity Bootstrap for QCD Amplitudes

We describe the recently developed on-shell bootstrap for computing one-loop amplitudes in non-supersymmetric theories such as QCD. The method combines the unitarity method with loop-level on-shell recursion. The unitarity method is used to compute cut-containing parts of amplitudes, and on-shell recursion is used for the remaining rational terms.

hep-ph↗

arXiv2006

Bootstrapping One-Loop QCD Amplitudes with General Helicities

The recently developed on-shell bootstrap for computing one-loop amplitudes in non-supersymmetric theories such as QCD combines the unitarity method with loop-level on-shell recursion. For generic helicity configurations, the recursion relations may involve undetermined contributions from non-standard complex singularities or from large values of the shift parameter. Here we develop a strategy for sidestepping difficulties through use of pairs of recursion relations. To illustrate the strategy, we present sets of recursion relations needed for obtaining n-gluon amplitudes in QCD. We give a recursive solution for the one-loop n-gluon QCD amplitudes with three or four color-adjacent gluons of negative helicity and the remaining ones of positive helicity. We provide an explicit analytic formula for the QCD amplitude A_{6;1}(1^-,2^-,3^-,4^+,5^+,6^+), as well as numerical results for A_{7;1}(1^-,2^-,3^-,4^+,5^+,6^+,7^+), A_{8;1}(1^-,2^-,3^-,4^+,5^+,6^+,7^+,8^+), and A_{8;1}(1^-,2^-,3^-,4^-,5^+,6^+,7^+,8^+). We expect the on-shell bootstrap approach to have widespread applications to phenomenological studies at colliders.

hep-ph↗

arXiv2006

On-shell Recursion Relations for n-point QCD

We present on the use of on-shell recursion relations. These can be used not only for calculating tree amplitudes, including those with masses, but also to compute analytically the missing rational terms of one-loop QCD amplitudes. Combined with the cut-containing pieces calculated using a unitarity approach complete one-loop QCD amplitudes can be derived. This approach is discussed in the context of the adjacent 2-minus all-multiplicity QCD gluon amplitude.

hep-ph↗

arXiv2006

All-Multiplicity Amplitudes with Massive Scalars

We compute two infinite series of tree-level amplitudes with a massive scalar pair and an arbitrary number of gluons. We provide results for amplitudes where all gluons have identical helicity, and amplitudes with one gluon of opposite helicity. These amplitudes are useful for unitarity-based one-loop calculations in nonsupersymmetric gauge theories generally, and QCD in particular.

hep-th↗

arXiv2006

All-Multiplicity One-Loop Corrections to MHV Amplitudes in QCD

We compute the complete one-loop corrections to the simplest class of QCD gluon amplitudes, those with two color-adjacent opposite-helicity external particles. We present results for an arbitrary number of external legs. The computation uses the recently-developed on-shell recursion relations for the rational parts, along with older unitarity-based results for the cut-containing terms.

hep-ph↗

arXiv2005

Twistor-Inspired Construction of Electroweak Vector Boson Currents

We present an extension of the twistor-motivated MHV vertices and accompanying rules presented by Cachazo, Svrvcek and Witten to the construction of vector-boson currents coupling to an arbitrary source. In particular, we give rules for constructing off-shell vector-boson currents with one fermion pair and n gluons of arbitrary helicity. These currents may be employed directly in the computation of electroweak amplitudes. The rules yield expressions in agreement with previously-obtained results for Z,W,γ^* --> qbar q + n gluons (analytically up to n=3, beyond via the Berends--Giele recursion relations). We also confirm that the contribution to a seven-point amplitude containing the non-abelian triple vector-boson coupling obtained using the next-to-MHV currents matches the previous result in the literature.

hep-ph↗