  In the framework of geometrothermodynamics, we explore how to construct an
inflationary cosmic fluid without requiring inflaton fields. To do so, we
employ standard radiation and matter as barotropic background, speculating on
the existence of a further real fluid, interpreted as a possible matter with
pressure constituent. We thus illustrate its main characteristics, showing how
it may face the flatness and horizon problems, yielding an equivalent number of
e-foldings, compatible with theoretical expectations. Moreover, we calculate
the associated equilibrium and kinetic temperatures, and compute
out-of-equilibrium properties, in terms of particle production and effective
reheating mechanism. Accordingly, we revise how inflation ends and how to fix
the free parameters of our model from observations. Last but not least, we
propose how to obtain a bare cosmological constant that could relate the
late-time acceleration to inflation, aiming to unify the two approaches.
Finally, we discuss the corresponding theoretical implications of our treatment
in contrast to the standard approach reliant on scalar field potentials,
emphasizing the main advantages and disadvantages.
