Congreso Colombiano de Astronomía y Astrofísica - 2012

The violation of the Suyama-Yamaguchi consistency relation: a smoking gun for cosmological inflationary models involving vector fields?

Not scheduled

15m

Grupo Halley (Universidad Industrial de Santander)

Presentaciones Orales Astronomía extragaláctica

Speaker

Dr César Alonso Valenzuela Toledo (Departamento de Física, Universidad del Valle, Ciudad Universitaria Meléndez, Santiago de Cali 760032, Colombia)

Description

In the context of inflationary cosmology, the study of the primordial curvature perturbation ζ allows us to characterize the statistical properties of the primordial seeds that gave origin to all the structures that we see today in our Universe [1]. In the standard and most accepted models, this quantity describes a distribution of the primordial fluctuations which is almost adiabatic, almost gaussian, and almost scale invariant, whereas it preserves the statistical homogeneity and isotropy. Any deviation from this behaviour can be used to parametrize effects related to the models proposed to describe cosmological inflation and provides us with valuable information to understand the agents that gave shape to the early Universe. On the other hand, in the standard cosmological inflationary models, inflation relies on the dynamics of one or several scalar fields, which, in principle, are the responsible of almost all statistical properties of the primordial curvature perturbation that we observe today in the Cosmic Microwave Background (CMB) [1]. While simple vector fields do not allow for an inflationary phase, they may still be present and let specific signatures that are potentially observable, such as a deviation from spatial isotropy and non-Gaussianity (NG) [2, 3]. A few years ago, a consistency relation involving two of the statistical descriptors for the primordial curvature perturbation ζ: the levels of NG in the bispectrum (fNL) and the trispectrum (τNL), was established, and, since then, it has been commonly called the Suyama-Yamaguchi (SY) consistency relation [4] (τNL^{iso} >= (6/5 fNL^{iso})^2). Its validity, originally established at tree-level [4], was extended quite recently to the non-linear regime [5], and its importance as a discriminator for inflationary models based on scalar fields was strongly remarked. So far, it has been shown that this consistency relation works, in principle, on models that only include scalar fields [4, 5] under just a few assumptions, but there is no any conclusive result for models that include other type of fields, for instance, vector fields (VF). Vector field models are particularly interesting because they are suitable candidates to explain the apparent violation of statistical isotropy observed in recent analysis of data from the WMAP satellite [6], given that VF define inherently a preferred direction for the expansion, for the distribution of primordial fluctuations, or for both [2, 7]. Because of this reason, it is pertinent to study consistency relations in models that include scalar fields as well as vector fields as these not only include NG parameters but also the amount of primordial statistical anisotropy g_\zeta [3]. Ref. [5] is particularly interesting since it claims that the SY consistency relation in the collapsed and squeezed limits is always satisfied independently of any physics; however, the proof depends sensitively on the assumption of scale-invariance which only applies for cosmological models involving scalar fields, leaving room for a potential violation of the consistency relation when VF are in charge of the generation of the primordial curvature perturbation. If such a violation is observationally confirmed, will we be in the presence of a smoking gun for such scenarios? References [1] D. H. Lyth and A. R. Liddle, The Primordial Density Perturbation: Cosmology, Inflation, and the Origin of Structure, Cambridge University Press, Cambridge - UK, 2009. [2] S. Yokoyama and J. Soda, JCAP 0808, 005 (2008); K. Dimopoulos, Phys. Rev. D 74, 083502 (2006); K. Dimopoulos, Int. J. Mod. Phys. D21 (2012) 1250023, Erratum-ibid. D21 (2012) 1292003; T. R. Dulaney and M. I. Gresham, Phys. Rev. D 81, 103532 (2010); A. E. Gumrukcuoglu, B. Himmetoglu, and M. Peloso, Phys. Rev. D 81, 063528 (2010); M.-a. Watanabe, S. Kanno, and J. Soda, Prog. Theor. Phys. 123, 1041 (2010). [3] M. Karˇciauskas, K. Dimopoulos, and D. H. Lyth, Phys. Rev. D 80, 023509 (2009); C. A. Valenzuela- Toledo, Y. Rodr ́ıguez, and D. H. Lyth, Phys. Rev. D 80, 103519 (2009); C. A. Valenzuela-Toledo and Y. Rodr ́ıguez, Phys. Lett. B 685, 120 (2010); E. Dimastrogiovanni et. al., Adv. Astron. 2010, 752670 (2010). [4] T. Suyama and M. Yamaguchi, Phys. Rev. D 77, 023505 (2008); N. S. Sugiyama, E. Komatsu, and T. Futamase, Phys. Rev. Lett. 106, 251301 (2011). [5] K. M. Smith, M. LoVerde, and M. Zaldarriaga, Phys. Rev. Lett. 107, 191301 (2011). [6] N. E. Groeneboom et. al., Astrophys. J. 722, 452 (2010). [7] C. A. Valenzuela-Toledo, Y. Rodr ́ıguez, and J. P. Beltr ́an Almeida, JCAP 1110, 020 (2011); K. Dimopoulos et. al., JCAP 0905, 013 (2009).

Presentation materials

Diapositivas

Charla_COCOA_2012.pdf