Constraining $f(T, \mathcal{T})$ gravity models using type Ia supernovae
  We present an analysis of an $f(T, \mathcal{T})$ extension of the Teleparallel Equivalent of General Relativity, where $T$ denotes the torsion and $\mathcal{T}$ the trace of the energy-momentum tensor. This extension includes non--minimal couplings between torsion and matter. In particular, we construct two specific models that recover the usual continuity equation, namely, $f(T, \mathcal{T})=T+g(\mathcal{T})$ and $f(T, \mathcal{T})=T\times g(\mathcal{T})$. We then constrain the parameters of each model by fitting the predicted distance modulus to that measured from type Ia supernovae, and find that both models can reproduce the late--time cosmic acceleration. We also observe that one of the models satisfies well the observational constraints and yields a goodness--of--fit similar to the $\Lambda$CDM model, thus demonstrating that $f(T,\mathcal{T})$ gravity theory encompasses viable models that can be an alternative to $\Lambda$CDM. 
Diego Saez-Gomez, C. Sofia Carvalho, Francisco S. N. Lobo and Ismael   Tereno
gr-qc astro-ph.CO