Dark Universe or twisted Universe? Einstein-Cartan theory. Thomas Schucker : CPT Marseille France Andre Tilquin : CPPM Marseille France THCA Tsinghua China \ arXiv:1104.0160 arXiv:1109.4568 2 Einstein general relativity: quick reminder Parallel transport and curvature Limitation in GR Einstein-Cartan general relativity Torsion: what is that? Parallel transport and torsion Properties and advantages Results on supernovae with a twisted Universe Solving Einstein-Cartan equations Effect of torsion on Hubble diagram Summary and further work 3 Related to curvature α B How to transport a vector or a frame in A1 a curve space? A2 A -Using this procedure on a reference frame and in the limit of a null surface defines the Einstein tensor: ๐บ๐๐ = ๐ ๐๐ − 1/2๐ ๐๐๐ which is symmetric in ๐๐ 4 -Geometry generates rotation Einstein equation relates curvature with energy momentum tensor ๐บ๐๐ = 8๐๐บ๐๐๐ As a consequence of symmetric Riemann geometry, the energy momentum tensor is symmetric: ๐๐๐ = ๐๐๐ General relativity can accommodate particle with spin including spin-1/2 using vierbein formalism (all tensors are represented in terms of a chosen basis of 4 independent orthogonal vectors field) However it can not describes spin-orbite coupling because when spin and orbital angular momentum are being exchanged, the momentum tensor is known to be nonsymmetric. According to the general equation of conservation of angular momentum: ๐๐๐ผ ๐๐ผ ๐ = ๐๐๐ − ๐ ๐๐ ≠ 0 Where ๐๐๐ − ๐ ๐๐ is the torque density = rate of conversion between orbital momentum and spin. Cartan => Torsion 5 * curvature torsion ๐′ ℵ = ๐. ๐ ๐ t t = −๐. ๐ ๐′ ๐ Cartan assumed that local torsion is related to spin ½ particles ℵ 6 translation α B A3 A1 A2 A -In presence of torsion the infinitesimal parallelogram does not close -Geometry generates translation 7 • Energy momentum is still the only source of space-time curvature with the Newton’s constant being the coupling constant • The source of torsion is half integer spin with the same coupling constant • Spin 1 particle is not source of torsion: photon not affected • Photon and spin ½ particle (neutrino) geodesics are different • Torsion doesn’t propagate • It’s non-vanishing only inside matter with half integer spin • Theories of unification between gravity and standard model of particle physics need a torsion field (loop quantum gravity) • Supergravity is an Eistein-Cartan theory. Without torsion this theory loses its supersymmetry. • Torsion provides a consistency description of general relativity 8 8๐๐บ๐๐๐ = Energy-momentum ๐บ๐๐ curvature Noether theorem geometry Translations rotations Noether theorem geometry Torsion spin Cartan equation 9 In space time with torsion there are 2 Einstein equations ( in vierbien frame): 1. Equation for curvature: ๐บ๐๐ = ๐ ∗ ๐๐ − 1/2๐ ∗ ๐๐๐ ๐บ๐๐ −∧ ๐๐๐ = 8๐๐บ๐๐๐ 2. Equation for torsion (Σ): Σ๐ ๐ ๐ ๐๐๐๐๐ = −8๐๐บ๐๐๐ R* is the modify Ricci tensor no more symmetric ๐๐๐ = spin tensor In a maximally symmetric Universe the most general energy momentum tensor has two functions of time: The density : ๐ ๐ก With equation of state: ๐ ๐ก โ ๐ค ๐(๐ก) The pressure : ๐ ๐ก The most general spin density Even parity : ๐0๐๐ = −๐ (๐ก)๐ฟ๐๐ ๐ ๐ก โ ๐ค๐ ๐ ๐ก With “equations of state”: ๐ ๐ก โ ๐ค๐ ๐(๐ก) Odd parity : ๐๐๐๐ = −๐ (๐ก)๐๐๐๐ 10 In maximally symmetric and flat Universe Friedmann equations have 4 unknown functions of time: a,b,f and ρ. ๐2 ๐ก − ๐ 2 (๐ก) 3 = Λ + 8๐๐บ๐ ๐ก ๐ 2 (๐ก) ๐′ (๐ก) ๐2 ๐ก − ๐ 2 (๐ก) 2 + = Λ − 8๐๐บ๐ ๐ก ๐(๐ก) ๐2 (๐ก) ๐′ ๐ก − ๐(๐ก) 3 = 8๐๐บ๐ค๐ ๐ ๐ก ๐(๐ก) ๐(๐ก) 2 = 8๐๐บ๐ค๐ ๐(๐ก) ๐(๐ก) Using these expressions today and the dimensionless density Ω = ๐(๐ก0) Ω๐ = 8๐๐บ๐0 3๐ป0 2 ; ΩΛ = Λ 3๐ป0 2 ; Ω๐ = ๐ค๐ ๐ป0 8๐๐บ๐0 3๐ป0 2 ; Ω๐ = ๐ค๐ ๐ป0 ๐๐ : 8๐๐บ๐0 3๐ป0 2 The Friedmann like closure relation reads: 9 Ω๐ + ΩΛ + 2Ω๐ − Ω๐ 2 + Ω๐ 2 = 1 4 11 Supernovae of type Ia are almost standard candle: There intrinsic luminosity (L) can be standardized at a level of about 15% Thus the apparent luminosity can be used as a distance indicator: ๐ ๐ก = ๐ฟ ๐(๐ก)2 4๐๐0 2 ๐ฅ(๐ก)2 ๐0 with ๐ฅ ๐ก = ๐ก0 ๐๐ก ′ ๐ก ๐(๐ก ′ ) And the redshift as a scale factor measurement: ๐0 ๐−๐ ๐ง = ๐(๐ก) −1 = ๐ 0 0 Because the geodesic equations for photons decouple to torsion, redshift and luminosity have the same expression ->We just need to compute the scale factor 12 We used the so called Union 2 sample containing 557 supernovae up to a redshift of 1.5 ๐ ๐ง = ๐๐ + 2.5log ๐ ๐ง Standard cosmology fit gives (no flatness): ms โฆm โฆΛ marginalized 0.35+0.10 −0.11 0.88+0.19 −0.11 13 We use the full covariance matrix, taking into account systematic errors and correlations to compute ๐ 2 = Δ๐๐ ๐ −1 Δ๐ ๐1 2 ๐= โฎ ๐๐1 ๐๐ ๐1 โฏ ๐1๐ ๐1 ๐๐ โฑ โฎ โฏ ๐๐ 2 ๐๐กโ ๐ง1 , Ω − ๐1 โฎ and Δ๐ = ๐๐กโ ๐ง๐ , Ω − ๐๐ The best cosmological parameters are computed by minimizing the ๐2: ๐๐ 2 =0 ๐Ω๐ Errors and contours are computed by using the frequentist prescription: ๐ 2 Ω๐ = min ๐ 2 (Ω๐ , Ω๐ , ๐๐ โฏ ) + ๐ 2 Ω๐ ,๐๐ โฏ Free cosmological parameters are: ๐๐ , Ω๐ , Ω๐ , Ω๐ where ΩΛ is deduced from Friedman like relation 9 Ω๐ + ΩΛ + 2Ω๐ − Ω๐ 2 + Ω๐ 2 = 1 4 14 Even parity torsion: Ω๐ = 0 โฆm โฆΛ ๐๐ 0.09+0.30 −0.07 0.83+0.10 −0.16 0.04+0.01 −0.07 โฆm โฆΛ Odd parity torsion: Ω๐ = 0 โฆm โฆΛ ๐๐ 0.27+0.03 −0.02 0.73+0.04 −0.11 0.0+0.22 −0.22 ๐๐ 0.08+0.27 −0.08 0.85+0.10 −0.15 0.04+0.02 −0.06 ๐๐ 0.0+0.1 −0.1 15 Even parity torsion gives a prefer value for matter density equal to 0.09 Ω๐ = 0.09+0.30 −0.07 The WMAP last results are: Ω๐ = 0.046 ± 0.003 and Ω๐ = 0.27 ± 0.03 Supernovae results analyzed with torsion give a result statistically compatible with both dark matter and baryonic matter. However, torsion can contribute to a certain amount of dark matter. Or better to say that torsion without dark matter is not incompatible with Supernovae data. More data or probes should be used to definitely conclude 16 We test the hypothesis of a null cosmological constant by using the log likelihood ratio technic: Assume we want to test 2 different models, with one include in the other: ๐ ๐ , Ω๐ , ΩΛ = 0 → ๐ ๐ , Ω๐ , ΩΛ We can define the log likelihood ratio as: ๐๐๐ฅ โ ๐๐ , Ω๐ , ΩΛ = 0 ๐ = −2๐ฟ๐ ๐คโ๐๐๐ โ = 2๐ ๐๐๐ฅ โ ๐๐ , Ω๐ , ΩΛ 1 ๐/2 ๐ ๐ −๐ 1/2 2 /2 ๐ = ๐ 2 ๐๐๐,1 − ๐ 2 ๐๐๐,2 The probability distribution of this variable is approximately a ๐ 2 distribution with a number of degree of freedom equal to the difference of ndof’s = 1 Fore even parity: Δ๐ 2 = 44.6 → ๐๐ฃ๐๐๐ข๐ ≅ 0. → ๐๐ข๐๐๐๐ ๐๐ข๐ก For odd parity : Δ๐ 2 = 30.3 → ๐๐ฃ๐๐๐ข๐ = 6 10−8 → ๐๐ข๐๐๐๐ ๐๐ข๐ก ๐๐ก 5.4 ๐ ๐๐๐๐ This is not surprising because equation of state: ๐ ๐ก โ ๐ค๐ ๐ ๐ก If acceleration today, then acceleration in the past: s ๐ก โ with ๐(๐ก) In contradiction with previous publication (S. Capozziello et al. 2003) 17 • Standard general relativity should be extended to account for spin-orbital momentum coupling: Einstein-Cartan theory. • If we apply torsion to cosmology we find: • Torsion can contribute to dark matter at a certain amount • Torsion as a source of dark energy is ruled out at more than 5 sigma • However these results are encouraging enough to try to go further • Look at galaxies rotation curves: Need to generalized the Schwarzschild’s equation. Work in progress. • Use other probes: • CMB/BAO/WL/Clusters: photons are not sensitive to torsion, but dynamic is different, so everything should be recomputed. ๏ • But we should not be too much excited by the Supernovae result on DM: We found a spin energy density Ω๐ of about 4% , corresponding to a state parameter ๐ค๐ ~1/๐ป0 ~1017 ๐ which is 42 orders of magnitude away from the โ −25 ๐ ! naïve value ๐ค๐ ~ 2 ~10 ๐๐ ๐ Usual problem in cosmology i.e : Λ and vacuum energy! 18 1) Torsion and curvature ? 2) Torsion and vacuum ? 19 In the general case, assuming no special equation of state: ๐ ๐ก ๐๐๐ ๐ ๐ก are free functions of time: ๐ 4๐๐บ 8๐๐บ ๐ ๐ก =− ๐ + 3๐ + ๐ ๐ก + ๐ (๐ก) ๐ 3 3 ๐ ๐ก Torsion is not source of gravity: Odd parity torsion doesn’t couple to dynamic (i.e curvature) Even parity torsion couple to curvature through kinematic not dynamic 20 (1) * 1. Because geodesics are different for photons and spin ½ particles (neutrino) • Timing difference between photons and neutrinos in supernovae explosion 1987A Supernovae • Neutrino oscillation experiment OPERA. Time delay and supra luminal neutrino 2. Rotation curve of galaxies or the modify Schwartsfield solution • What is the effect of torsion on rotation curve of galaxy 3. Galaxies and cluster formation 4. The cosmological probes: • Supernovae 1a • CMB: effect of torsion in initial plasma (very high matter density) • Weak lensing should not be affected Lensing is gravitational coupling between curvature and photon • Baryonic acoustic oscillation Depends on the initial power spectrum 21 Let consider the covariant derivative of a vector:๐ด๐ ๐ป๐ ๐ด๐ = ๐ด๐ ,๐ + Γ๐๐ ๐ ๐ด๐ with ๐ด๐ ,๐ = ๐๐ด๐ /๐๐ฅ ๐ = ๐๐ ๐ด๐ Where Γ๐๐ ๐ is the affine connection This covariant derivative can be formally written as: ๐ฟ๐ ๐ ๐ป๐ = ๐ฟ๐ ๐ ๐๐ + Γ๐๐ ๐ And compare to covariant derivative in QED: ๐ท๐ = ๐๐ +๐๐๐ด๐ In geometric term, the affine connection is interpreted as the change of vector during parallel transport along ๐๐ฅ๐ : −Γ๐๐ ๐ ๐ด๐ ๐๐ฅ ๐ And the curvature tensor is defined as the change of vector ๐ด๐ parallel transported around a closed path ๐๐ โถ Δ๐ด๐ = 1 ๐ ๐ด ๐ ๐ฝ๐๐ ๐ 2 ๐๐ ๐๐ฅ ๐ฝ 22 โ = ๐๐ ๐๐๐ ๐ ∗ −๐2 ๐๐ ∗ This Lagrangian is invariant under global rotation ๐ in complex plane: θ θ ๐ → ๐๐ −๐๐ θ ๐ ∗ → ๐ ∗ ๐ ๐๐ → ๐๐ ∗ is invariant ๐๐ ๐ → ๐๐ ๐๐ −๐๐ θ ๐๐ ๐ ∗ → ๐๐ ๐ ∗ ๐ ๐๐ → ๐๐ ๐๐๐ ๐ ∗ is invariant But is not invariant under local rotation ๐ ๐ฅ๐ in complex plane: θ ๐๐ ๐ → ๐๐ ๐. ๐ −๐๐ − ๐๐๐ ๐ ๐ฅ๐ . ๐. ๐ −๐๐ = ๐๐ ๐ = Variation of the field is assumed to be linear in ๐ ๐๐๐ ๐ฟ๐ฅ๐ : + Δ๐ ๐ฟ๐ฅ ๐ Δ๐ = −๐๐๐ด๐ ๐ฟ๐ฅ ๐ ๐ + ๐ท๐ ๐ ๐ท๐ = ๐๐ + ๐๐๐ด๐ 23 ๐ ๐ผ − Γ๐๐ ๐ผ ๐ ๐ ๐ ๐ ๐ต๐ผ = ๐ ๐ผ + (๐ ๐ผ − Γ๐๐ ๐ผ ๐ ๐ ๐ ๐ ) ๐ ๐ผ − Γ๐๐ ๐ผ ๐๐ ๐ ๐ ๐๐ผ ๐ด๐ผ = ๐ ๐ผ + (๐ ๐ผ − Γ๐๐ ๐ผ ๐๐ ๐ ๐ ) ๐๐ผ Then the difference ๐ถ ๐ผ = ๐ด๐ผ − ๐ต๐ผ is: ๐ถ ๐ผ = 2๐๐๐ ๐ผ ๐๐ ๐ ๐ 1 with ๐๐๐ ๐ผ = Γ[๐๐] ๐ผ = 2 Γ๐๐ ๐ผ − Γ๐๐ ๐ผ Where ๐๐๐ ๐ผ is defined as the torsion tensor 24 ๐ ๐ก โ ๐ค๐ ๐ ๐ก ๐ ๐ก โ ๐ค๐ ๐(๐ก) • ๐ ๐ก = any spin ½ matter density with null pressure • ๐ ๐ก = spin density considered as a perfect fluid! • ๐ค๐ has a dimension of time and is assumed to be constant All physics are inside ws: • Source of torsion is spin ½ particle • Orbital momentum or spin 1 are not source of torsion. • No spin orbital momentum coupling. Spin generates local torsion. • It contains the Planck constant and GR and QM coupling. Expected to be small. • We assume it is not zero even though we don’t know how spins average? • ……… 25 ๐ 2 ๐ก − ๐ 2 (๐ก) 3 = Λ + 8๐๐บ๐ ๐ก ๐2 (๐ก) ๐ ′ (๐ก) ๐ 2 ๐ก − ๐ 2 (๐ก) 2 + = Λ ๐(๐ก) ๐2 (๐ก) ๐′ ๐ก − ๐(๐ก) 3 = 8๐๐บ๐ค๐ ๐ ๐ก ๐(๐ก) ๐(๐ก) 2 = 8๐๐บ๐ค๐ ๐(๐ก) ๐(๐ก) We eliminate f(t) and ρ(t) We are left with 2 first order differential equations and 2 unknown functions a(t) and b(t) We solve it numerically with the Runge-Kutta algorithm. a(t) This is an iterative numerical algorithm Example: 1. a’(t) = 2 a(t) a1 2. Start from an initial value a(t0)=a0 3. Compute the derivative a’(t0)=2 a0 a0 4. Predict the new point at t0+δt using Tailor expansion : a(t1 = t0+δt) = a0+2a0 δt +…..= a1 5. Start from this new value a(t1)=a1 and iterate t0 t1=t0+δt t We used a forth order Runge-Kutta algorithm with an adaptive step in time such that the corresponding step in redshift is much smaller than the experimental 26 redshift error (10-5) In this paper they assume the same Friedmann equations for the torsion fluid ๐ 4๐๐บ =− ๐ + 3๐ ๐ = ๐ + ๐ 2 ๐๐๐ ๐ = ๐ − ๐ 2 ๐ 3 with 2 ๐ 8๐๐บ = ๐ ๐ 3 3 The missing factor 3 implies torsion is source of curvature and a constant “f” function with time which can be interpreted as a cosmological constant. At beginning I made the same kind of mistake and I got ๏ Unfortunately it’s wrong! 27 In general case where s(t) and ๐ ๐ก are functions of time we have: ๐ 1 = Λ − 4๐๐บ ๐ + 3๐ ๐ 3 8๐๐บ ๐ + ๐ ๐ก + ๐ (๐ก) 3 ๐ • Odd parity torsion ๐ (๐ก) doesn’t modify dynamic (Einstein curvature) • Even parity torsion couple to gravit 28 The Hilbert action yields the Einstein equation through the principle of least action: 1 ๐=− 2๐ 4 ๐ −๐๐ ๐ฅ R the Ricci scalar ๐ = ๐๐๐ก ๐๐๐ ๐ = 8๐๐บ๐ −4 with In presence of matter the action becomes: ๐= 1 ๐ + โ๐ 2๐ −๐๐ 4 ๐ฅ The action principle ๐ฟ๐ = 0 leads to: ๐ฟ๐ = ๐ฟ −๐โ ๐ 1 ๐ฟ −๐๐ + 2๐ ๐ฟ๐๐๐ ๐ฟ๐๐๐ ๐ฟ๐ = 1 ๐ฟ๐ ๐ ๐ฟ −๐ + 2๐ ๐ฟ๐๐๐ −๐ ๐ฟ๐๐๐ ๐ฟ๐๐๐ ๐ 4 ๐ฅ + 1 ๐ฟ −๐โ๐ −๐ ๐ฟ๐๐๐ 29 ๐ฟ๐๐๐ −๐๐4 ๐ฅ Since the previous equation should hold for any ๐ฟ๐๐๐ ๐ฟ๐ ๐ ๐ฟ −๐ 1 ๐ฟ −๐โ๐ + = −2๐ ๐ฟ๐๐๐ −๐ ๐ฟ๐๐๐ −๐ ๐ฟ๐๐๐ ๐ฟ๐ = ๐ ๐๐ ๐ฟ๐๐๐ 1 ๐ฟ −๐ 1 = − ๐ −๐ ๐ฟ๐๐๐ 2 ๐๐ ๐๐๐ −2 ๐ฟ −๐โ๐ ๐ฟโ๐ โ = −2 ๐๐ + ๐๐๐ โ๐ −๐ ๐ฟ๐๐๐ ๐ฟ๐ 1 8๐๐บ ๐ ๐๐ − ๐๐๐ ๐ = 4 ๐๐๐ 2 ๐ The cosmological constant is introduced in the Lagrangian: ๐= 1 ๐ − 2Λ + โ๐ 2๐ 1 8๐๐บ ๐ ๐๐ − ๐๐๐ ๐ + Λ๐๐๐ = 4 ๐๐๐ 2 ๐ −๐๐4 ๐ฅ 30