Photo-emission from sQGP Sang-Jin Sin (Hanyang Beijing, 2010/10/22 Based on K.Jo + SJS arXiv: X.Ge, M. Matsuo, F.Shu,T.Tsukioka, sjs arXiv:

Two main difficulties in Nuclear Physics * Coupling is large. Hard to do reliable calculation * Many particle system  difficulty even at lattice QCD * Need New idea

AdS/QCD : gives mean field theory that does not require loop calcuation. The stonger the better. Penalty: it is Holographic (5d) Originally N=4 SUSY For the strong coupling problem, the ans. is the Gauge/Gravity Duality

Consequences of duality Gluon dynamics is replaced by ads gravity. Exact Correlation function can be calculated by the classical eq. (but in 5d curved space).  Transports (more later), Phase transition(SC,CSB)

Relativistic Heavy Ion Collider Au-Au collision E~200 GeV/nucleon Seek quark-gluon plasma(QGP)

Early interests: 4 puzzles Perfect fluid : ( , ) Jet quenching ( hep-th/ ) elliptic flow ( hep-th/ ) * Early thermalization ( hep-th/ ) These are puzzles from the aspect of AF but clues to use AdS/CFT. phenomena-(my contributions)

Usefulness of ads/cft: understanding Perfect fluidity While perturbative evaluation ~1/g^4 Exp: ads/cft : Universal value

What about LHC? Is the medium still strongly interacting ? If mass production mechanism is too efficient, increasing initial energy does not help to increase the Temp. much. For Hadron sprectrum, we expect it is the same as the RHIC since they reprent the moment of the freezout.

Photon & Lepton On the other hand photons and leptons can expose the early stage of the fireball.  Photoemission spectral functions are interesting. Strong v.s Weak are very different. (Huot et.al, hepth/ ). No density effect of the medium.

In this talk Dense matter effect in Photoemission rate based on the work with KwangHyun Jo.(my student) Claim: density effect is yet another interesting effect: LPM and beyond. Understand why such dramatic change happens.

Photoemission rate and duality Huot et.al hepth/

Photo prod. in weak g Sum of 2-2, Bremstrahlung,pair annihilation LPM effect yet to be corrected

Lepton production

SYM v.s QCD in weak g Huot et.al hepth/

Zero density result Huot et.al hepth/

Finite density K.Jo + SJS arXiv:

density effect in spectral function

To understand Why, Look Hydro dynamic analysis, which gives the analytic result for the spectral function for small w and k.

In hqcd Finite temperature quark-gluon plasma  Black hole Dense matter  Charged black hole we use RN balck hole. (for the relevance to the baryonic system, see [arXiv: (sjs)] Bulk filling brane idea.

AdS R-N black hole Solution to the eq. of M:

Match: BH  QGP Temperature, entropy, energy pressure, charge density and chemical pot.

Perturbations around RN perturbed Eintein eq. & Maxwell eq. X.GeX.Ge, Y.Matsuo, F.Shu, SJS,Takuya Tsukioka, arXiv: Y.MatsuoF.ShuTakuya Tsukioka

perturbed Maxwell eq. Gauge choice and Fourier mode

Classification of modes(for graviton)

Vector type pert and mode mixing.

Infalling BC at horizon  Causal Gr.F perturbative solution near boundary  Hydrodynamic

Mixing effect: Correlation functions in hydro limit transverse v.s longitudinal

Remark In the absence of charge, particle current is NOT diffusive (a=0 or T=0) while heat current is !

Summary of hydro Result: Density causes Mode Mixing, which establishes diffusion pole. We expect that it enhences spectral function of photon at low frequency.

Density effect in photo emmision

LPM(Landau- Pomeranchuk-Migdal) Suppression of Brehmstrahlung due to the density effect. (B is not point like process) Q: Is it encoded here? We think so. Decrease in the peak at low density. Notice: after certain critical density, photoemission increases.

Some details for spectral function calculation for vector mode

Effective action4 In falling BC at horizon: D=0,C=1

relevant case introduce

density effect in spectral function (again)

Ac and DC Conductivities

Density effect in spectral function Remember: The hydro peak is absent if density is 0.

Conclusion String theory may be useful for the New experiment. Photoemssion spectral curve is Analogy of CMBR curve in cosmology LPM effect is counted and different high density effect is predicted.