Now showing items 1-20 of 44

    • An extended matter bounce scenario: current status and challenges 

      Haro Cases, Jaume; Cai, Yi-Fu (2015-08-01)
      Article
      Open Access
      As an alternative to the paradigm of slow roll inflation, we propose an extended scenario of the matter bounce cosmology in which the Universe has experienced a quasi-matter contracting phase with a variable background ...
    • ANÀLISI FUNCIONAL 

      Haro Cases, Jaume (Universitat Politècnica de Catalunya, 2007-06-29)
      Exam
      Restricted access to the UPC academic community
    • Bouncing cosmologies in geometries with positively curved spatial sections 

      Haro Cases, Jaume (Elsevier, 2016-09-10)
      Article
      Open Access
      Background bouncing cosmologies, driven by a single scalar field, having a quasi-matter domination period during the contracting phase, i.e., depicting the so-called Matter Bounce Scenario, are reconstructed for cosmologies ...
    • Bouncing cosmologies via modified gravity in the ADM formalism: Application to loop quantum cosmology 

      Haro Cases, Jaume; Amorós Torrent, Jaume (American Physical Society (APS), 2018-03-15)
      Article
      Open Access
      We consider the Arnowitt-Deser-Misner formalism as a tool to build bouncing cosmologies. In this approach, the foliation of the spacetime has to be fixed in order to go beyond general relativity modifying the gravitational ...
    • Bouncing loop quantum cosmology from F(T) gravity 

      Amorós Torrent, Jaume; Haro Cases, Jaume; Odintsov, Sergei D. (2013-05)
      Article
      Open Access
      The big bang singularity could be understood as a breakdown of Einstein’s general relativity at very high energies. By adopting this viewpoint, other theories that implement Einstein cosmology at high energies might solve ...
    • Bouncing loop quantum cosmology in Gauss-Bonnet gravity 

      Haro Cases, Jaume; Makarenko, A. M.; Myagky, A. N.; Odintsov, Sergei D.; Oikonomou, V. K. (American Physical Society, 2015-12-11)
      Article
      Open Access
      We develop an effective Gauss-Bonnet extension of loop quantum cosmology, by introducing holonomy corrections in modified F(G) theories of gravity. Within the context of our formalism, we provide a perturbative expansion ...
    • Brane cosmology from observational surveys and its comparison with standard FRW cosmology 

      Astashenok, Artyom V.; Elizalde, Emilio; Haro Cases, Jaume; Odintsov, Sergei D.; Yurov, Artyom V. (2013-09)
      Article
      Restricted access - publisher's policy
      Several simple dark energy models on the brane are investigated. They are compared with corresponding models in the frame of 4d Friedmann-Robertson-Walker cosmology. For constraining the parameters of the models considered, ...
    • Bulk viscous quintessential inflation 

      Haro Cases, Jaume; Pan, Supriya (2018-04-01)
      Article
      Open Access
      In a spatially-flat Friedmann–Lemaître–Robertson–Walker universe, the incorporation of bulk viscous process in general relativity leads to an appearance of a nonsingular background of the universe that both at early and ...
    • Calculation of the renormalized two-point function by adiabatic regularization 

      Haro Cases, Jaume (2010-11)
      Article
      Restricted access - publisher's policy
      We calculate a renormalized two-point function using the adiabatic regularization method. We study the conformally and minimally coupled cases for massless and massive scalar fields in full detail. We reproduce previous ...
    • Can quantum effects due to a massless conformally coupled field avoid gravitational singularities? 

      Haro Cases, Jaume (2012-04)
      Article
      Restricted access - publisher's policy
      Using quantum corrections from massless fields conformally coupled to gravity, we study the possibility of avoiding singularities that appear in the flat Friedmann–Robertson–Walker model. We assume that the universe ...
    • Cosmological perturbations in a class of fully covariant modified theories: application to models with the same background as standard LQC 

      Haro Cases, Jaume; Aresté Saló, Llibert; Elizalde, Emilio (Springer, 2018-09-01)
      Article
      Open Access
      Bouncing cosmologies are obtained by adding to the Einstein–Hilbert action a term of the form -g---vf(¿), with ¿ a scalar depending on the Hubble parameter only, not on its derivatives, and which is here shown to arise ...
    • Cosmological solutions in spatially curved universes with adiabatic particle production 

      Aresté Saló, Llibert; Haro Cases, Jaume (2017-02-20)
      Article
      Open Access
      We perform a qualitative and thermodynamic study of two models when one takes into account adiabatic particle production. In the first one, there is a constant particle production rate, which leads to solutions depicting ...
    • Different reheating mechanisms in quintessence inflation 

      Haro Cases, Jaume (American Physical Society (APS), 2019-02-11)
      Article
      Open Access
      Different well-known ways to reheat the Universe, such as instant preheating, the creation of particles nearly or conformally coupled with gravity, or from the decay of products of a curvaton field, are revisited and ...
    • Evolution and dynamics of a matter creation model 

      Pan, Supriya; Haro Cases, Jaume; Paliathanasis, A.; Slagter, R.J. (2016-05-01)
      Article
      Open Access
      In a flat Friedmann–Lemaître–Robertson–Walker (FLRW) geometry, we consider the expansion of the universe powered by the gravitationally induced ‘adiabatic’ matter creation. To demonstrate how matter creation works well ...
    • Gravitational particle production in bouncing cosmologies 

      Haro Cases, Jaume; Elizalde, Emilio (2015-10-13)
      Article
      Open Access
      © 2015 IOP Publishing Ltd and Sissa Medialab srl . It is argued that the Universe reheating in bouncing cosmologies could be explained via gravitational particle production, as due to a sudden phase transition in the ...
    • Gravitational Particle Production in Massive Chaotic Inflation and the Moduli Problem 

      Haro Cases, Jaume; Elizalde, Emilio (2012-02)
      Article
      Restricted access - publisher's policy
      Particle production from vacuum fluctuations during inflation is briefly revisited. The moduli problem occurring with light particles produced at the end of inflation is addressed, namely the fact that some results are in ...
    • Gravitationally induced adiabatic particle production: from big bang to de Sitter 

      Haro Cases, Jaume (2016-07-27)
      Article
      Open Access
      In the background of a flat homogeneous and isotropic space–time, we consider a scenario of the Universe driven by the gravitationally induced 'adiabatic' particle production with constant creation rate. We have shown that ...
    • How can holonomy corrections be introduced in f(R) gravity? 

      Haro Cases, Jaume (2014-07-08)
      Article
      Open Access
      We study the introduction of holonomy corrections in f(R) gravity. We will show that there are infinitely many ways, as many as canonical transformations, to introduce this kind of corrections, depending on the canonical ...
    • Inflation and late-time acceleration from a double-well potential with cosmological constant 

      Haro Cases, Jaume; Elizalde, Emilio (2016-06-01)
      Article
      Open Access
      A model of a universe without big bang singularity is presented, which displays an early inflationary period ending just before a phase transition to a kination epoch. The model produces enough heavy particles so as to ...
    • Limiting curvature mimetic gravity and its relation to Loop Quantum Cosmology 

      Haro Cases, Jaume; Aresté Saló, Llibert; Pan, Supriya (2019-04-01)
      Article
      Open Access
      Considering as usual that the underlying geometry of our universe is well described by the spatially flat Friedmann–Lemaître–Robertson–Walker line element, we review how the background of holonomy corrected Loop Quantum ...