GLinAlternativeModelsSG < ICRA

---+ Gravitational lensing in alternative cosmological models - Beyond &Lambda;CDM
---+ Lentes gravitacionais em modelos cosmológicos alternativos ao &Lambda;CDM

Some driving questions:
   * How do the constraints on &gamma; propagate into constraints on specific modified gravity models? Which (classes of) models can be discarded by strong lensing (SL)?
   * Can we write the lens equation in a simple form in non-homogeneous universes (e.g. spherically symmetric, LTB models)?
   * To what extent, can SL in multiple lines-of-sight constrain inhomogeneous models?
   * Are there models with different high-z behavior for which the SL tests would be more stringent?
   * What are the constraints on specific classes of MOG models from the combination of SL with other data (e.g. gravity waves, extra-solar planets, other cosmological probes)

*Suggested reading lists*

General MOG refs and cosmological tests (see also CosmoObs.TheoryRefs):
   * Jain, Bhuvnesh; Khoury, Justin, 2010, _Cosmological tests of gravity_, Annals of Physics, 325, 1479 (ADS [[http://adsabs.harvard.edu/abs/2010AnPhy.325.1479J][link]])
   * Jain, Bhuvnesh, et al., 2013, _Novel Probes of Gravity and Dark Energy_, [[http://arxiv.org/abs/1309.5389][arXiv:1309.5389]]
   * DE and Modified Gravity: Austin Joyce, Lucas Lombriser, Fabian Schmidt, 2016, _Dark Energy vs. Modified Gravity_, [[http://arxiv.org/abs/1601.06133][arXiv:1601.06133]]
   * Status of ΛCDM: Philip Bull, et al., 2015, _Beyond ΛCDM: Problems, solutions, and the road ahead_, [[http://arxiv.org/abs/1512.05356][arXiv:1512.05356]]

Examples of SL constraining cosmology and !MoG: see CosmoObs.CosmoSL


Potentially relevant papers for extending the lens equation to inhomogeneous cosmologies:
   * G. Fanizza, M. Gasperini, G. Marozzi and G. Veneziano, _An exact Jacobi map in the  geodesic light-cone gauge_, JCAP 1311, 019 (2013) [doi:10.1088/1475-7516/2013/11/019, arXiv:1308.4935]
   * G. Fanizza and F. Nugier, _Lensing in the geodesic light-cone coordinates and its (exact) illustration to an off-center observer in Lemaître-Tolman-Bondi models_, JCAP 1502, 002 (2015) [doi:10.1088/1475-7516/2015/02/002, arXiv:1408.1604]

Below are two inspiring plots that motivate this group in light of the observational constraints on modified gravity.
BTW, the recent Gravitational Wave results strengthen the importance of using cosmology to constrain the gravity theory, as they are complementary to those derived from GW ("This improves on Solar System and binary pulsar bounds [98,99] by factors of a few and a thousand, respectively, but does not improve on the model-dependent bounds derived from the dynamics of Galaxy clusters [100] and weak lensing observations [101]" [PRL 116, 061102 (2016)]). 

     <img src="%PUBURLPATH%/%WEB%/%TOPIC%/GravityScales.png" alt="GravityScales.png" width="725" height="520" />

Tests of gravity at diferent length scales.  Red lines shows observations that probe
the sum of metric potentials via weak and strong gravitational lensing or the ISW effect.  Blue
lines  show  dynamical  measurements  that  rely  on  the  motions  of  stars  or  galaxies  or  other
non-relativistic tracers. [Fig. 8 from Jain, Bhuvnesh; Khoury, Justin, 2010, _Cosmological tests of gravity_, Annals of Physics, 325, 1479 (ADS [[http://adsabs.harvard.edu/abs/2010AnPhy.325.1479J][link]])]


     <img src="%PUBURLPATH%/%WEB%/%TOPIC%/mg_limits.png" alt="mg_limits.png" width="838" height="722" />

Astrophysical [64, 38, 39] and cosmological [89, 90, 91] limits on chameleon theories.  The spatial
scale on the x-axis gives the range of length scales probed by particular experiments.  The parameter on the
y-axis is the background field value, or the range of the interaction (y-axis label on the right side) for an
_f(R)_ model of the accelerating universe.  The rectangular regions give the exclusion zone from a particular
experiment. All but the solar system results have been obtained in the last 5 years, illustrating the impressive
interplay between theory and experiment in the field. The two rectangles with dots are meant to indicate
preliminary results from ongoing work.  
[Fig. 2 from Jain, Bhuvnesh, et al., 2013, _Novel Probes of Gravity and Dark Energy_, [[http://arxiv.org/abs/1309.5389][arXiv:1309.5389]] (adapted from Lombriser et al. 2012, Phys.Rev.,
D85:102001)]

Notes on modifications of GR:
   * Horndeski: Horndeski, IJTP 1974; Kobayashi et al. 2011
   * Beyond Horndeski: PRLm 2015, %$\gamma_{\rm PPN} = \frac{1+\alpha_H}{c_T}$%, %$G_N = \frac{c_T^4}{8M^2 (1+\alpha_H)^2}$%
   * Vainshtein
   * Chamaleon, D. Mota, PLB, 2004; Khoury, PRL

Invited members: Felipe Tovar, Habib Dúmet, Miguel Quartin, Santiago Bergliaffa, Marcelo Vargas, Vanessa Pacheco (?); Remotos (?): Vinicius Bragança, Marcos Lima, Hermano Velten, Cristofher Zuñiga

-- Main.MartinMakler - 2016-02-03
Attachments
Topic attachments
I	Attachment	Action	Size	Date	Who	Comment
png	GravityScales.png	manage	60.4 K	2016-03-01 - 01:41	MartinMakler	Fig. 8 from Jain, Bhuvnesh; Khoury, Justin, 2010, Cosmological tests of gravity
png	mg_limits.png	manage	97.2 K	2016-03-01 - 01:52	MartinMakler	Fig. 2 from Jain, Bhuvnesh, et al., 2013 (adapted from Lombriser et al. 2012)
Topic revision: r10 - 2019-04-07 - MartinMakler
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