The angular homogeneity scale of the Universe - Centre for

35 Pages·2013·7.69 MB·English

by  Alicia Bueno

The angular homogeneity
scale of the Universe
Alicia Bueno Belloso
ITP, Heidelberg
Work in collaboration with:
David Alonso, Juan García-Bellido, Eusebio Sánchez and Javier Sánchez
in preparation

2nd of September 2013
DAMTP, Cambridge
Introduction: a homogeneous
or fractal universe?
•  Usual assumption: the Universe is homogeneous and isotropic on large scales
Alicia Bueno Belloso The angular homogeneity scale of the Universe 2nd September 2013
Introduction: a homogeneous
or fractal universe?
•  Usual assumption: the Universe is homogeneous and isotropic on large scales
•  Homogeneous regime is not realised on small scales, due to the form of the
spectrum of matter perturbations and to their evolution via gravitational collapse.
Alicia Bueno Belloso The angular homogeneity scale of the Universe 2nd September 2013
Introduction: a homogeneous
or fractal universe?
•  Usual assumption: the Universe is homogeneous and isotropic on large scales
•  Homogeneous regime is not realised on small scales, due to the form of the
spectrum of matter perturbations and to their evolution via gravitational collapse.
•  The primordial spectrum of metric perturbations is predicted to be almost
scale-invariant by inflation, still expect some level of inhomogeneities
Alicia Bueno Belloso The angular homogeneity scale of the Universe 2nd September 2013
Introduction: a homogeneous
or fractal universe?
•  Usual assumption: the Universe is homogeneous and isotropic on large scales
•  Homogeneous regime is not realised on small scales, due to the form of the
spectrum of matter perturbations and to their evolution via gravitational collapse.
•  The primordial spectrum of metric perturbations is predicted to be almost
scale-invariant by inflation, still expect some level of inhomogeneities
•  Different groups have argued that the Universe might not reach homogeneity
on large scales, and that it behaves like a fractal…
Pietronero. et al., 1997, Critical Dialogues in Cosmology, 24
F. Sylos Labini, et al., Europhys. Letters 2009
Alicia Bueno Belloso The angular homogeneity scale of the Universe 2nd September 2013
Introduction: a homogeneous
or fractal universe?
•  Usual assumption: the Universe is homogeneous and isotropic on large scales
•  Homogeneous regime is not realised on small scales, due to the form of the
spectrum of matter perturbations and to their evolution via gravitational collapse.
•  The primordial spectrum of metric perturbations is predicted to be almost
scale-invariant by inflation, still expect some level of inhomogeneities
•  Different groups have argued that the Universe might not reach homogeneity
on large scales, and that it behaves like a fractal…
•  … while other groups claim the opposite result!!
Pietronero. et al., 1997, Critical Dialogues in Cosmology, 24 Scrimgeour, M., et al., 2012, MNRAS, 425, 116
F. Sylos Labini, et al., Europhys. Letters 2009 Nadathur, S. 2013, MNRAS, 434, 398
Alicia Bueno Belloso The angular homogeneity scale of the Universe 2nd September 2013
Introduction: a homogeneous
or fractal universe?
•  To measure this transition observationally, large survey volume is necessary
Alicia Bueno Belloso The angular homogeneity scale of the Universe 2nd September 2013
Introduction: a homogeneous
or fractal universe?
•  To measure this transition observationally, large survey volume is necessary
•  Ideal for photometric galaxy redshift surveys such as DES
The Dark Energy Survey Collaboration, arXiv:0510346, 2005
Alicia Bueno Belloso The angular homogeneity scale of the Universe 2nd September 2013
Introduction: a homogeneous
or fractal universe?
•  To measure this transition observationally, large survey volume is necessary
•  Ideal for photometric galaxy redshift surveys such as DES
Due to photometric uncertainty
Radial information is lost
The Dark Energy Survey Collaboration, arXiv:0510346, 2005
Alicia Bueno Belloso The angular homogeneity scale of the Universe 2nd September 2013
Introduction: a homogeneous
or fractal universe?
•  To measure this transition observationally, large survey volume is necessary
•  Ideal for photometric galaxy redshift surveys such as DES
Due to photometric uncertainty
Radial information is lost
Must use estimator with only angular info
Advantage: Angles are model-independent!
The Dark Energy Survey Collaboration, arXiv:0510346, 2005
Alicia Bueno Belloso The angular homogeneity scale of the Universe 2nd September 2013