Browsing by Author "San Martín Hormazábal, Marco"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    An Accelerating Universe without Lambda: Delta Gravity Using Monte Carlo
    (2019) Alfaro Solís, Jorge Luis; San Martín Hormazábal, Marco; Sureda Hernández, Joaquín Miguel
    A gravitational field model based on two symmetric tensors, gμν and g˜μν , is studied, using a Markov Chain Monte Carlo (MCMC) analysis with the most updated catalog of SN-Ia. In this model, new matter fields are added to the original matter fields, motivated by an additional symmetry ( δ˜ symmetry). We call them δ˜ matter fields. This theory predicts an accelerating Universe without the need to introduce a cosmological constant Λ by hand in the equations. We obtained a very good fit to the SN-Ia Data, and with this, we found the two free parameters of the theory called C and L2 . With these values, we have fixed all the degrees of freedom in the model. The last H0 local value measurement is in tension with the CMB Data from Planck. Based on an absolute magnitude MV=−19.23 for the SN, Delta Gravity finds H0 to be 74.47±1.63 km/(s Mpc). This value is in concordance with the last measurement of the H0 local value, 73.83±1.48 km/(s Mpc).
  • Thumbnail Image
    Item
    Observational constraints in Delta Gravity : CMB and supernovas
    (2020) San Martín Hormazábal, Marco; Alfaro Solís, Jorge Luis; Pontificia Universidad Católica de Chile. Facultad de Física
    I study the cosmological implications of Delta Gravity (DG), which is a gravitational model based on the extension of General Relativity (GR) by a new symmetry called δ ̃. In this model, new matter fields are added to the original matter fields, motivated by the additional symmetry. We call them δ ̃ matter fields. This theory predicts an accelerating Universe without introducing a Cosmological Constant Λ by hand in the equations. To test the Delta Gravity implications, I examine two critical observations in Cosmology: the rate of the Universe expansion through type Ia supernovae (SNe-Ia) and the power spectrum calculated from the cosmic microwave background radiation (CMB). To compare the observations with these model's predictions, I used a Markov Chain Monte Carlo (MCMC) analysis with the most updated SNe-Ia and Planck satellite data catalog. I obtain the fitted parameters needed to explain both SNe-Ia data and CMB measurements. I analyze the DG model's compatibility with both observations and constrain the cosmological parameters associated with the astrophysical evidence. Finally, I discuss if the Hubble Constant and the Accelerating Universe are compatible with the DG context's observational evidence.