L. Perivolaropoulos - PowerPoint Presentation

Slide1

L. Perivolaropouloshttp://leandros.physics.uoi.grDepartment of PhysicsUniversity of Ioannina

Open page

Collaborators: I. Antoniou (Ioannina)J. Bueno-Sanchez (Madrid)J. Grande (Barcelona) S. Nesseris (Madrid)A. Mariano (Lecce)

Accelerating Expansion of the Universe from Topological

SolitonsSlide2

Main Points

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 observerin 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

.Slide3

3FRW Metric

Universe Description

Homogeneous-Isotropic System+ PerturbationsGeneral RelativityTwo Parameters: Geometry ( Curvature k=-1,0,+1), Scale (Scale Factor a(t))

Closed

Flat

Open

Universe Expands

Flat: Favored by Observations and TheorySlide4

4

Dynamics: The Dark Energy Puzzle

General RelativityDirectlyObservableDirectlyObservableDark Energy(Inferred)Q: Is GR the correct theory on the Largest Scales?What is the Correct Theory?

What are the properties of the dark energy?

What microphysical theory can reproduce these properties?

No

Yes

Flat

Friedmann EquationSlide5

The scale factor

α(

t) and the redshift zHubble’s Law (z<<1):Photons from distant galaxies have a larger redshiftSlide6

Hubble’s Law

(1929): The Universe is ExpandingSlide7

The observed evolution of α(t)

a(t)

tAcceleratingUniverset0present

0

t

0

Decelerating

Universe

Decelerating expansion due to attractive gravity of matter

Accelerating expansion due to

???

Empty Universe

Discovery

1998 (

SCP,

HzSST

)

Nobel: 2011 (

Perlmutter

, Schmidt,

Riess

)Slide8

Why is the Universe Accelerating?Slide9

Einstein (1915) General Relativity: Gμν

= κ T

μν Cosmological Constant + Matter :Gmn - L gmn = k TmnCosmological ConstantCosmological Constant: The simplest model

Cosmic Repulsion

(

p

Λ

=-

ρ

Λ

c

2

)

Acceleration of scale factorSlide10

10

Equation of State:

Quintessence: Homogeneous Scalar FieldHomogeneous Scalar Field Dynamics:Repulsive gravity and accelerating expansion from the negative pressure of a homogenous scalar fieldPotential resolution of Coincidence Problem (why cosmological constant is so small to lead to acceleration only recently?)Slide11

11

Direct Probes of the Cosmic Metric:Geometric Observational Probes

Luminosity Distance (standard candles: SnIa,GRB):Angular Diameter Distance (standard rulers: CMB sound horizon, clusters):

SnIa

Obs

GRB

flat

Direct Probes of H(z):Slide12

Geometric Constraints

Parametrize H(z):

Minimize:Slide13

Consistency of

ΛCDM with Data

Good Agreement with Geometric Probes!SNLSESSENCE

GOLD06

UNION

CONSTITUTION

WMAP5+SDSS5

WMAP7+SDSS7

UNION2

J. C.

Bueno

Sanchez, S.

Nesseris

, LP,

JCAP 0911:029,2009,

0908.2636 Slide14

Puzzling Data

Puzzles for

ΛCDM are related to the existence of a preferred axisA. Kashlinsky et. al. Astrophys.J.686:L49-L52,2009 arXiv:0809.3734Quadrupole component of CMB mapOctopole component of CMB mapDipole component of CMB map

M.

Tegmark

et

. al

.,

PRD 68, 123523 (2003),

Copi

et. al.

Adv.Astron.2010:847541,2010

. 

Dark Velocity Flow

Λ

CDM prediction

WMAP Cosmic Microwave Background mapSlide15

Puzzles for

ΛCDM

Large Scale Velocity Flows - Predicted: On scale larger than 50 h-1Mpc Dipole Flows of 110km/sec or less. - Observed: Dipole Flows of more than 400km/sec on scales 50 h-1Mpc 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, 0811.4684,I. Antoniou, LP, JCAP 1012:012, 2010, arxiv:1007.4347R. Watkins et. al. , Mon.Not.Roy.Astron.Soc.392:743-756,2009, 0809.4041. A. Kashlinsky et. al. Astrophys.J.686:L49-L52,2009 arXiv:0809.3734A. Mariano, LP, ,

Phys.Rev

. D86 (2012) 083517

,

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~10-5

- Probability of Consistency: 0.0

1%

Webb et. al.. , Phys. Rev. Lett. 107, 191101 (2011)

M. Tegmark et. al.,

PRD 68, 123523 (2003), Copi et. al. Adv.Astron.2010:847541,2010. Slide16

Cosmic Anisotropy Axes

Dark Flow Direction

(3σ)Watkins et. al. arxiv: 0809.4041, Kashlinsky et. al. arxiv: 0809.3734WMAP7 CMB Map – Maximum Temperature Asymmetry (1.5 σ) (A. Mariano, LP,  arXiv:1211.5915 Phys. Rev. D. 87, 043511 (2013))α Dipole (4σ)Webb et. al. , Phys. Rev. Lett. 107, 191101 (2011)Q1: How anomalous is this coincidence?

Q2: Is there a physical model that can predict this coincidence

Dark Energy Dipole (2

σ)

A. Mariano, LP, ,

Phys.Rev

. D86 (2012) 083517

.

Slide17

Basic Issues

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 106.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?Slide18

Models Predicting a Preferred Axis

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))Slide19

Coincidence Problem: Why Now? Time Dependent Dark EnergyAlternatively:

Why Here? Inhomogeneous Dark Energy

Inhomogeneous Dark Energy: Why Consider?Standard Model (ΛCDM):1. Homogeneous - Isotropic Dark and Baryonic Matter.2. Homogeneous-Isotropic-Constant Dark Energy (Cosmological Constant)3. General RelativityConsider Because:1. New generic generalization of ΛCDM (breaks homogeneity of dark energy). Includes ΛCDM as special case.Natural emergence of preferred axis (off – center observers)Well defined physical mechanism (topological quintessence with Hubble scale global monopoles).J. Grande, L.P., Phys. Rev. D 84,  023514 (2011).J. B. Sanchez, LP, Phys.Rev. D84 (2011) 123516 Slide20

Topological Quintessence

Global Monopole with Hubble scale Core

General Metric with Spherical Symmetry:Energy – Momentum Tensor:Slide21

Global Monopole Configuration

Global Monopole: Field Direction in Space and Energy Density

Off-center ObserverVariation of expansion rate due to dark energy density variationVariation of α?Slide22

Extended Topological Quintessence

Global Monopole Configuration:

Non-minimally coupled scalar fieldFine Structure Constant:Fine Structure Constant Spatial Variation: Slide23

Global Monopole Configuration

Global Monopole: Field Direction in Space and Energy Density

Off-center ObserverVariation of α due to field variationVariation of expansion rate due to dark energy density variationSlide24

Model Parameters

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) 123516Slide25

Full Dynamical Equations

Initial-Boundary Conditions

Energy-Momentum ConservationStatic Monopole Profile (Φ=f(r) )Homogeneous, Flat Matter Dominated (A=B=1)Slide26

Main Questions

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?Slide27

Energy Densities

Monopole energy density slowly shrinks and dominates at late times in the core.

Matter develops underdensity at the core.Slide28

Scale Factors

η=0.1

Mpl η=0.6 Mpl η=0.1 Mpl η=0.6 Mpl Accelerating Expansion at the core.r=0r=0.5

r=5Slide29

Summary

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 observerin 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. Slide30

Simplest Model:

Lematre-Tolman-Bondi

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

Central Observer

Apparent AccelerationSlide31

Shifted Observer: Preferred Direction

Faster expansion rate at low

redshifts (local space equivalent to recent times)Local spherical underdensity of matter (Void)

Observer

Preferred DirectionSlide32

Luminosity Distance

Metric:

Cosmological Equation:Geodesics:Luminosity Distance:

FRW limit:

MSlide33

Constraints: Union2 Data – Central Observer

Advantages:

1. No need for dark energy.2. Natural Preferred Axis.3. Coincidence ProblemJ. Grande, L.P., Phys. Rev. D 84,  023514 (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) 041301 )