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L. Perivolaropoulos http://leandros.physics.uoi.gr Department of Physics University of Ioannina

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## L. Perivolaropoulos http://leandros.physics.uoi.gr Department of Physics University of Ioannina

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From Type Ia Supernovae

L. Perivolaropouloshttp://leandros.physics.uoi.gr

Department of Physics

University of Ioannina

Dist. Ind.

Expansion History from

Luminosity Distance

Absolute luminocity L: Total Power Radiated

Apparent luminocity l:

Luminocity Distance:

Physical Distance

in Static Universe

Expanding Universe:

comoving distance

Luminosity Distance

Expanding Universe:

1

Light Geodesics

2

1

2

Know L

Measure l(z)

Distance Modulus:

Supernova Cosmology Project (SCP)

S. Perlmutter et. al. (Berkeley)

High-z Supernova Search Team (HZT)

B. Schmidt et. al. (Mt. Stromlo Obs.)

Higher-z Supernova Search Team (HZT)

A. Riess et. al. (Space Telescope Sci. Inst.)

Supernova Acceleration Probe (SNAP)

S. Perlmutter et. al. (Berkeley)

Future Space Satellite

ESSENCE

C. Stubbs et. al. (Harvard)

Canada-France-Hawaii Legacy Survey

Accelerating Universe:

(rate of expansion) was smaller in the past.

Thus H-1(t) was larger in the past.

Standard Candles

SNeIa

Luminus Objects of a given redshift

appear to be further away (dimmer)

in an Accelerating Universe

Distance Indicators (Standard Candles)

Expand. Phot. Meth./SnII

Best Choicefor Cosmology

Planetary Nebulae

Surf. Brightness Fluct.

Tully Fisher

Brightest Cluster Gal.

Glob. Cluster Lum. Fun.

Sunyaev-Zeldovich

Gravitational Lensing

1. Exceedingly Luminus

2. Small Dispersion of peak amplitude

3. Good understanding of Explosion Mechanism

4. Small Cosmic Evolution Expected

Degeneracy pressure always fails at same mass.

5. Local Tests for Calibration

Problem:

Predict a SnIa Explosion

1-2 SnIa per galaxy per millenium

1. Observe a number of empty sky

wide fields (~10000 gal)

2. Observe same patch after

three weeks.

3. Subtract Images to identify

12-14 SnIa

4. Schedule Follow-up Photometry

and Spectroscopy

HST

SnIa follow similar light curves

(similar luminosities)

Q: How can we distiguish the

small luminosity differences?

closeby SnIa

A: Streched lightcurves - brighter SnIa

Contracted lightcurves - fainter SnIa

Verify Strech Factor-Brightness Correlation:

Contract while reducing peak luminosity

Stretch while increasing peak luminosity

SnIa Luminosity Corrections II

SnIa spectra appear shifted due to

Hubble expansion

Apply proper filters to compare time evolution

of the same part of the spectrum

Apply K-Correction.

Also, a time interval dt at redshift z corresponds

to a time interval dt (1+z) at present time.

Correct light curve

timescale for

cosmological time dilation

Q: What (other than distance) could be

making high-z SnIa dimmer?

No! Dust absorbs blue light more than red light.

Distant SnIa have similar spectra as nearby SnIa.

Could it be Dust?

No! The diming does not continue to

amplify at z>0.5

Could it be Grey Dust?

No! The time evolution of SnIa

spectrum is identical for close and for distant SnIa.

Could it be Evolution of SnIa?

Gold Dataset (157 SNeIa):

Riess et. al. 2004

dust produced from vacuum with time

Expansion History of the Universe

Expected:

Decelerated Expansion due to Gravity

Observed:

Accelerated Expansion

Q: What causes the Acceleration?

Acceleration from

Dynamics of scale factor a(t):

Friedman eqn

General Relativity

Homogeneity-Isotropy

Equation of State:

Necessary condition for acceleration:

Dark Energy

Antigravity

Dark Energy

Energy Conservation:

Friedman Equation

Best Fit ?

(from large scale structure observations)

w=-1

Gmn = k Tmn

- Einstein (1915) G.R.:
- Einstein (1917) G.R. + Static Universe + Matter only:

Gmn- L gmn = k Tmn

Cosmic Repulsion

Cosmological Constant

Then came:

Hubble's Discovery (1929)

- The biggest blunder of my life

Einstein :

Since I introduced this term, I had always a bad conscience....

I am unable to believe that such an ugly thing is actually realized in nature

A. Einstein 1947 letter to Lemaitre

1. Measurements of the Cosmological Parameters Omega and Lambda

from the First 7 Supernovae at z >= 0.35S. Perlmutter et al., Astrophys.J. 483 (1997) 565

2. Observational Evidence from Supernovae for anAccelerating Universe and a Cosmological ConstantS. Perlmutter et al., Nature 391 (1998) 51

3. Discovery of Supernova Explosion at Half the Age of the Universe A.G. Riess et al., Astron.J. 116 (1998) 1009-1038

4. Cosmological results from high-z supernovaeTonry et al. The Astrophysical Journal, 594:1-24, 2003 September 1

5. New Constraints on ΩM, ΩΛ, and w from an Independent Set of 11 High-Redshift Supernovae Observed with the Hubble Space TelescopeR.A. Knop et al., The Astrophysical Journal, Volume 598, Issue 1, pp. 102-137

11 new SnIa observed from HST

6. Type Ia Supernova Discoveries at z > 1 From the Hubble SpaceTelescope: Evidence for Past Deceleration and Constraints on Dark Energy Evolution

A. Riess et al. The Astrophysical 607:665-687,2004

16 new SnIa observed from HST7 of them with z>1.25

Decelerating Expansion starts at z=0.46

Metamorphosis

Statistical Fluctuations

can produce data

that indicate metamorphosis even within LCDM

Metamorphosis

Statistical Fluctuations even within 68%

can produce data

that indicate metamorphosis even within LCDM

Metamorphosis

Statistical Fluctuations even within 68%

can produce data

that indicate metamorphosis even within LCDM

LCDM is the simplest model consistent with current data

Dark Energy Metamorphosis is

Less Apealing Theoretically

But

Is more probable than LCDM on the basis of current data

< 1σ

Q: How much more probable?

< 2σ

> 1σ

Questions

What theory produces the features of best parametrizations?

What is the Fate of the Universe? (extrapolating w(z) to z<0 (w(z)<-1))

- Quintessence: tracking scalar fields (Ratra & Peebles, Wetterich 1988, Coble et al. 1997, Ferreira & Joyce 1998, Liddle & Scherrer 1999, Steinhardt et al. 1999, Perrotta & Baccigalupi 1999, Brax & Martin 2000, Masiero et al. 2001, Doran et al. 2001, Corasaniti & Copeland 2003,Perivolaropoulos 2005,Tsujikawa 2005)
- Extended Quintessence: non-minimal coupling to Gravity (Chiba, Uzan 1999, Perrotta et al. 2000, Baccigalupi et al. 2000, Faraoni 2000, Bartolo & Pietroni 2000, Esposito-Farese & Polarski 2001, Perrotta & Baccigalupi 2002, Perivolaropoulos 2005,Tsujikawa 2005)
- Coupled Quintessence: coupling with dark matter (Carroll 1998, Amendola 2000, Matarrese et al. 2003)
- k-essence: modified kinetic scalar field energy (Aramendariz-Picon et al. 2001, Caldwell 2002, Malquarti et al. 2003)

- Quantum Fluctuations of Scalar Field: (Onemli and Woodard 2004)
- Spacetime microstructure: self-adjusting spacetime capable to absorb vacuum energy (Padmanabhan, 2002)
- Matter-Energy Transition: dark matter undergoes a phase transition to dark energy at low redshifts (Basset et al. 2003)
- Brane worlds: brane tension (Shani & Sthanov 2002, Sami & Dadhich 2004, Brown, Maartens Papantonopoulos, & Zamarias 2005); cyclic-ekpyrotic cosmic vacuum (Steinhardt &Tutok 2001)
- Exotic particle physics: photons oscillating in something else at cosmological distances (Csaki et al. 2002)
- Chaplygin gas: dark matter and energy described by a single gas having variable equation of state (Den et al. 2003, Carturan & Finelli 2003)
- Scale-dependent Gravity: Gravity weaker on large scales (Dvali et al. 2003)

No w=-1 crossing

Homogeneous Minimally

Coupled Scalar:

+: Quintessence

-: Phantom

Equation of State:

To cross the w=-1 line the kinetic energy term

must change sign

(impossible for single phantom or quintessence field)

Linear Potential V(Φ) = s Φ

Scalar Field:

No crossing of w=-1 line

(poor fits)

Crossing the w=-1 line

(better fits e.g. scalar tensor theories)

L.P., astro-ph/0504582

Best Scalar Fit:

Big Rip

Bound Systems in Expanding Background:

Radial Geodesics:

S. Nesseris, L. P., Phys.Rev.D70:123529,2004

Repulsion Increases with time

for w<-1

Big Rip

Repulsion Explodes at t*~w/(w+1)

- 2m Telescope
- ~1 billion pixels, 144 CCDs
- 350-1700 nm wavelength coverage
- Finds and follows 2500 SnIa each year, out to z = 1.7
- Place good limits on both w and its time evolution

- Dark Energy with Negative Pressure can explain SnIa cosmological data indicating accelerating expansion of the Universe.
- The existence of a cosmological constant is consistent with SnIa data but other evolving forms of dark energy crossing the w=-1 line provide better fits to the data.
- New observational projects are underway and are expected to lead to significant progress in the understanding of the properties of dark energy.

We measure shadows, and we search among ghostly errors ofmeasurement for landmarks that are scarcely more substantial. The search will continue.

E. Hubble in The Realm of the Nebulae,

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