L. Perivolaropoulos Department of Physics University of Ioannina Open page Collaborators: I. Antoniou (Ioannina) J. Bueno-Sanchez (Madrid) J. Grande (Barcelona) S. Nesseris (Madrid) A. Mariano (Lecce)

The expansion of the Universe has entered an accelerating phase during recent cosmological times. Repulsive gravity on large scales is needed to explain this accelerating expansion. This may be provided by the ΛCDM model. There are some puzzling conflicts between ΛCDM predictions and some cosmological observations (Galaxy Velocity Flows, Cosmic Microwave Background Temperature Asymmetry, Fine Structure Constant Dipole, Dark energy Dipole) Most of these puzzles are related to the existence of preferred anisotropy axes which appear to be surprisingly close to each other! The simplest mechanism that can give rise to a cosmological preferred axis is based on an off-center observer in a spherical energy inhomogeneity (dark matter or dark energy) Topological Quintessence is a simple physical mechanism that can give rise to a Hubble scale dark energy inhomogeneity.

3 FRW Metric Two Parameters: Geometry ( Curvature k=-1,0,+1), Scale (Scale Factor a(t)) Closed Flat Open Universe Expands

4 Directly Observable Dark Energy (Inferred) No Yes Flat Friedmann Equation

The scale factor α(t) and the redshift z Hubble’s Law (z<<1): Photons from distant galaxies have a larger redshift

Hubble’s Law (1929): The Universe is Expanding

The observed evolution of α(t) a(t) t Accelerating Universe t0t0 present 0 t0t0 Decelerating Universe Decelerating expansion due to attractive gravity of matterAccelerating expansion due to ??? Empty Universe Discovery 1998 (SCP, HzSST) Nobel: 2011 (Perlmutter, Schmidt, Riess)

Why is the Universe Accelerating?

Einstein (1915) General Relativity: G μν = κ T μν Cosmological Constant + Matter : G  -  g  =  T  Cosmological Constant: The simplest model Cosmic Repulsion (p Λ =-ρ Λ c 2 ) Acceleration of scale factor

10 Equation of State: Repulsive gravity and accelerating expansion from the negative pressure of a homogenous scalar field Potential resolution of Coincidence Problem (why cosmological constant is so small to lead to acceleration only recently?)

11 Luminosity Distance (standard candles: SnIa,GRB): Angular Diameter Distance (standard rulers: CMB sound horizon, clusters): SnIa Obs GRB flat Direct Probes of H(z):

Parametrize H(z): Minimize:

Good Agreement with Geometric Probes! SNLS ESSENCE GOLD06 UNION CONSTITUTION WMAP5+SDSS5 WMAP7+SDSS7 UNION2 J. C. Bueno Sanchez, S. Nesseris, LP, JCAP 0911:029,2009,

Puzzles for ΛCDM are related to the existence of a preferred axis A. Kashlinsky et. al. Astrophys.J.686:L49- L52,2009 arXiv: Quadrupole component of CMB map Octopole component of CMB mapDipole component of CMB map M. Tegmark et. al., PRD 68, (2003), Copi et. al. Adv.Astron.2010:847541,2010. Dark Velocity Flow ΛCDM prediction WMAP Cosmic Microwave Background map

Large Scale Velocity Flows - Predicted: On scale larger than 50 h -1 Mpc Dipole Flows of 110km/sec or less. - Observed: Dipole Flows of more than 400km/sec on scales 50 h -1 Mpc or larger. - Probability of Consistency: 1% Anisotropy of Cosmic Accelerating Expansion - Predicted: Isotropic Rate of Accelerating Expansion - Observed: SnIa data show hints for an anisotropic acceleration fit by a Dipole - Probability of Consistency: 5% From LP, , I. Antoniou, LP, JCAP 1012:012, 2010, arxiv: R. Watkins et. al., Mon.Not.Roy.Astron.Soc.392: ,2009, A. Kashlinsky et. al. Astrophys.J.686:L49-L52,2009 arXiv: A. Mariano, LP,, Phys.Rev. D86 (2012) , Alignment of Low CMB Spectrum Multipoles - Predicted: Multipole components of CMB map should be uncorrelated. - Observed: l=2 and l=3 CMB map components are unlikely planar and close to each other. - Probability of Consistency: 1% Cosmic Spatial Dependence of the Fine Structure Constant - Predicted: The value of the Fine Structure Constant is Space-Time Independent. - Observed : There is a cosmic spatial dependence well fit by a Dipole with δα/α~ Probability of Consistency: 0.01% Webb et. al.., Phys. Rev. Lett. 107, (2011) M. Tegmark et. al., PRD 68, (2003), Copi et. al. Adv.Astron.2010:847541,2010.

Dark Flow Direction (3σ) Watkins et. al. arxiv: , Kashlinsky et. al. arxiv: WMAP7 CMB Map – Maximum Temperature Asymmetry (1.5 σ) (A. Mariano, LP, arXiv: Phys. Rev. D. 87, (2013) ) α Dipole (4σ) Webb et. al., Phys. Rev. Lett. 107, (2011) Q1: How anomalous is this coincidence?Q2: Is there a physical model that can predict this coincidence Dark Energy Dipole (2σ) A. Mariano, LP,, Phys.Rev. D86 (2012)

A1: The probability that the combined quasar absorber and SnIa data are obtained in the context of a homogeneous and isotropic cosmology is less than one part in A2: There is a simple physical model based on a Hubble scale topological defect non-minimally coupled to electromagnetism that has the potential to explain the observed aligned dipoles. Q1: What is the probability to produce the observed combination of just the two dipoles in a homogeneous-isotropic cosmological model? Q2: What physical model has the potential to predict the existence of the above combined dipoles?

Anisotropic dark energy equation of state (eg vector fields) (T. Koivisto and D. Mota (2006), R. Battye and A. Moss (2009)) Fundamentaly Modified Cosmic Topology or Geometry (rotating universe, horizon scale compact dimension, non-commutative geometry etc) (J. P. Luminet (2008), P. Bielewicz and A. Riazuelo (2008), E. Akofor, A. P. Balachandran, S. G. Jo, A. Joseph,B. A. Qureshi (2008), T. S. Koivisto, D. F. Mota, M. Quartin and T. G. Zlosnik (2010)) Statistically Anisotropic Primordial Perturbations (eg vector field inflation) (A. R. Pullen and M. Kamionkowski (2007), L. Ackerman, S. M. Carroll and M. B. Wise (2007), K. Dimopoulos, M. Karciauskas, D. H. Lyth and Y. Ro-driguez (2009)) Horizon Scale Primordial Magnetic Field. (T. Kahniashvili, G. Lavrelashvili and B. Ratra (2008), L. Campanelli (2009), J. Kim and P. Naselsky (2009)) Horizon Scale Dark Matter or Dark Energy Perturbations (eg few Gpc void) (J. Garcia-Bellido and T. Haugboelle (2008), P. Dunsby, N. Goheer, B. Osano and J. P. Uzan (2010), T. Biswas, A. Notari and W. Valkenburg (2010))

Coincidence Problem: Why Now? Time Dependent Dark Energy Alternatively: Why Here? Inhomogeneous Dark Energy Standard Model (ΛCDM): 1. Homogeneous - Isotropic Dark and Baryonic Matter. 2. Homogeneous-Isotropic-Constant Dark Energy (Cosmological Constant) 3. General Relativity Consider Because: 1. New generic generalization of ΛCDM (breaks homogeneity of dark energy). Includes ΛCDM as special case. 2.Natural emergence of preferred axis (off – center observers) 3.Well defined physical mechanism (topological quintessence with Hubble scale global monopoles). J. Grande, L.P., Phys. Rev. D 84, (2011). J. B. Sanchez, LP, Phys.Rev. D84 (2011)

Global Monopole with Hubble scale Core General Metric with Spherical Symmetry: Energy – Momentum Tensor:

Global Monopole: Field Direction in Space and Energy Density Off-center Observer Variation of expansion rate due to dark energy density variation Variation of α?

Global Monopole Configuration: Non-minimally coupled scalar field Fine Structure Constant: Fine Structure Constant Spatial Variation:

Global Monopole: Field Direction in Space and Energy Density Off-center Observer Variation of α due to field variationVariation of expansion rate due to dark energy density variation

Monopole Core Scale: Potential Energy Density at the Core: Approximate Cosmic Evolution at the Core: Approximate Cosmic Evolution away from the Core: Physical Requirements: Cosmological Scale Core Core Density similar as present matter density J. B. Sanchez, LP,, Phys.Rev. D84 (2011)

Initial-Boundary Conditions Energy-Momentum Conservation Static Monopole Profile (Φ=f(r) ) Homogeneous, Flat Matter Dominated (A=B=1)

Does the Monopole Energy Density Eventually Dominate over matter in the Monopole Core? Does the possible domination lead to accelerating expansion in the monopole core? Can this cosmological expansion in the core fit the cosmological data?

1.Monopole energy density slowly shrinks and dominates at late times in the core. 2.Matter develops underdensity at the core.

η=0.1 M pl η=0.6 M pl η=0.1 M pl η=0.6 M pl Accelerating Expansion at the core. r=0 r=0.5 r=5

Early hints for deviation from the cosmological principle and statistical isotropy are being accumulated. This appears to be one of the most likely directions which may lead to new fundamental physics in the coming years. The simplest mechanism that can give rise to a cosmological preferred axis is based on an off-center observer in a spherical energy inhomogeneity (dark matter of dark energy) Such a mechanism can also give rise to large scale velocity flows and Fine Structure Constant Dipole. Other interesting effects may occur (quasar polarization alignment etc). Topological Quintessence constitutes a physical mechanism to produce Hubble scale dark energy inhomogeneities.

Faster expansion rate at low redshifts (local space equivalent to recent times) Local spherical underdensity of matter (Void), no dark energy Central Observer Apparent Acceleration

Faster expansion rate at low redshifts (local space equivalent to recent times) Local spherical underdensity of matter (Void) Observer Preferred Direction

Metric: Cosmological Equation: Geodesics: Luminosity Distance: FRW limit: M

Advantages: 1. No need for dark energy. 2. Natural Preferred Axis. 3. Coincidence Problem J. Grande, L.P., Phys. Rev. D 84, (2011). Problems: 1. No simple mechanism to create such large voids. 2. Off-Center Observer produces too large CMB Dipole. 3. Worse Fit than LCDM. 4. Ruled out by kSZ – CMB (Zhang and Stebbins, Phys.Rev.Lett. 107 (2011) )