1. LABORATORY INVESTIGATIONS INTO THE EXTREME UNIVERSE Pisin Chen Stanford Linear Accelerator Center Stanford University Introduction Universe as Laboratory Laboratory Studies of the Universe Summary Second ORION Workshop, SLAC, Feb. 18-20, 2003.

2. LABORATORY ASTROPHYSICS Its relationship with Astrophysics, Particle Physics, and Plasma Physics

3. National Research Council Committee on the Physics of the Universe: Connecting Quarks with the Cosmos: Eleven Science Questions for the New Century What is the dark matter? What is the nature of the dark energy? How did the universe begin? Did Einstein have the last word on gravity? What are the masses of the neutrinos, and how have they shaped the evolution of the universe? How do cosmic accelerators work and what are they accelerating? Are protons unstable? Are there new states of matter at exceedingly high density and temperature? Are there additional spacetime dimensions? How were the elements from iron to uranium made? Is a new theory of matter and light needed at highest energies?

4. High Energy-Density Physics Long history of Plasma Astrophysics (Alfven waves, etc.) Modern frontier: Very high density, high pressure, and high temperature astrophysical environments and plasma processes Newly emerged discipline: High Energy-Density Physics

5. “Eleven Science Questions” and Extreme Astrophysical Conditions Extremely high energy events, such as ultra high energy cosmic rays (UHECR), neutrinos, and gamma rays Very high density, high pressure, and high temperature processes, such as supernova explosions and gamma ray bursts (GRB) Super strong field environments, such as that around black holes (BH) and neutron stars (NS) Particle astrophysics and cosmology partially overlaps with high energy-density physics through some of these connections

6. Symbiosis between Direct Observations and Laboratory Investigations Symbiosis should still be true for Particle Astrophysics and Cosmology Classic example: Laboratory determination of stellar evolution 4p 4 He + 2e + + 2ν e + ~ 25 MeV

7. Three Categories of LabAstro -Using Lasers and Particle Beams as Tools - 1. Calibration of observation - Precision measurements to calibrate observation processes - Development of novel approaches to astro-experimentations - Though mundane, value to astrophysics most certain 2. Investigation of dynamics - Astro-conditions hard to recreate in lab - Many MHD or plasma processes scalable by extrapolation - Value lies in revelation of dynamical underpinnings 3. Probing fundamental physics - Underlying physical principles may yet to be developed - Extreme limits render signatures faint; viability uncertain - Issues at stake too fundamental to be ignored for experimentation

8. UNIVERSE AS A LABORATORY - Extremely High Energy Events - Ultra High Energy Cosmic Rays (UHECR) - “Knee” and “ankle” in UHECR spectrum - Events beyond GZK-limit found Very high energy ν’s and γ’s - ν masses and oscillations - Extremely high energy γ : violation of Lorentz invariance? “Is a new theory of matter and light needed at the highest energies?”

9. UHECR: From Source to Detection “How do cosmic accelerators work and what are they accelerating?” Δ

10. Greisen-Zatsepin-Kuzmin Limit Protons above 6×10 19 eV will lose sizable energy through CMB Super-GZK events have been found with no identifiable local sources 3×10 20 eV 50 Mpc ~ Size of local super-cluster

11. Cosmic Acceleration Mechanisms Conventional cosmic acceleration mechanisms encounter limitations: - Fermi acceleration (1949) (= stochastic accel. bouncing off B-fields) - Diffusive shock acceleration (70s) (a variant of Fermi mechanism) Limitations for UHE: field strength, diffusive scattering inelastic - Eddington acceleration (= acceleration by photon pressure) Limitation: acceleration diminishes as 1/γ New thinking: - Zevatron (= unipolar induction acceleration) (R. Blandford) - Alfven-wave induced wakefield acceleration in relativistic plasma (Chen, Tajima, Takahashi, Phys. Rev. Lett. 89, 161101 (2002).) - Additional ideas by M. Barring, R. Rosner, etc.

12. UNIVERSE AS A LABORATORY - Ultra High Energy-Density Processes -  Shock Neutrino-plasma coupling Neutrinosphere (proto-neutron star) Plasma pressure  Bingham, Dawson, Bethe, Phys. Lett. A, 220, 107 (1996) Phys. Rev. Lett., 88, 2703 (1999) Supernova explosion

13. Gamma Ray Burst Release of ~ 10 52 erg/sec (short bursts)! “Standard” relativistic fireball model (Rees-Meszaros, 92, 93) Extended model invokes quark-gluon plasma (Chen et al., 01) “Are there new states of matter at exceedingly high density and temperature?”

14. UNIVERSE AS A LABORATORY - Super Strong Field Environment - Black holes and strong gravitational field - Testing general relativity “Did Einstein have the last word on gravity?” Neutron stars and strong EM fields - Schwinger critical field: B c ~ 4×10 13 G or E c ~ 10 16 V/m - QED Vacuum unstable

15. UNIVERSE AS A LABORATORY - Extreme Limits of Spacetime and Vacuum - ~2/3 of the present energy density of the universe is in “dark energy”. “What is the nature of dark energy?” Quantum effects of gravity becomes sizable, or spacetime becomes unrest, at Planck scale. “Are there additional spacetime dimensions?” Planck scale ~10 -35 m Human scale ~ 1m

16. LABORATORY STUDIES OF THE UNIVERSE Suggested in 2001 Workshop on Laboratory Astrophysics (very preliminary): 1. Cline (UCLA): Primordial Black Hole Induced Plasma Instability Expt. 2. Sokolsky (Utah): High Energy Shower Expt. for UHECR 3. Kirkby (CERN): CLOUD Expt. on Climate Variation 4. Chen-Tajima (SLAC-Austin): Plasma Wakefield Acceleration Expt. for UHECR 5. Nakajima (KEK): Laser Driven Dirac Acceleration for UHECR Expt. 6. Odian (SLAC): Non-Askaryan Effect Expt. 7. Rosner (Chicago): Astro Fluid Dynamics Computer Code Validation Expt. 8. Colgate-Li (LANL): Magnetic Flux Transport and Acceleration Expt. 9. Kamae (SLAC): Photon Collider for Cold e + e – Plasma Expt. 10. Begelman-Marshall (CO-MIT): X-Ray Iron Spectroscopy and Polarization Expt. 11. Ng (SLAC): Relativistic e + e – Plasma Expt. 12. Katsouleas (USC): Beam-Plasma Interaction Induced Photon Burst Expt. 13. Blandford (CalTech): Beam-Plasma Filamentation Instability Expt. 14. Scargle (NASA-Ames): Relativistic MHD Landau Damping Expt. POSSIBLE LABORATORY ASTROPHYSICS EXPERIMENTS

17. LABORATORY STUDIES OF THE UNIVERSE - Calibration of Observation - 1. Fluorescence from UHECR induced showers - Two methods of detec- tion: Fly’s eye (HiRes) & ground array(AGASA) - Next generation UHECR detector Pierre Auger invokes hybrid detections - Future space-based observatories use fluorescence detection

19. SLAC E-165 Experiment Fluorescence in Air from Showers (FLASH) HiRes-SLAC-CosPA (Taiwan) collaboration

20. 2. Neutrino Astrophysics and the Askaryan Effect - During high-energy EM cascade, γ’s and e - ’s pull e - ’s in from surrounding material - e + ’s, on the other hand, annihilate in flight - The two effects lead to a net charge in the shower - Strong coherent radio and microwave Cherenkov emission (First observation at SLAC, Saltzberg, et al., Phys. Rev. Lett., 2000) - Novel method for UHECR and ν detections (Saltzberg-Gorham) 3. Heavy Element X-Ray Spectroscopy Three “lucky breaks” in black hole accretion: 1. (Many) accretion flows are “cold”; 2. Accretion disks are not fully ionized; 3. Accretion disks are illuminated by flaring coronae. “X-ray observations will allow us to probe the spacetimes of black holes in detail” (M. Begelman)

21. (M. Begelman, 01)

22. LABORATORY STUDIES OF THE UNIVERSE - Investigation of Underlying Dynamics - 1. Alfven-Wave induced Plasma Wakefield Accel. Expt. (Chen et al., 01) Generation of Alfven waves in relativistic plasma flow Inducing high gradient nonlinear plasma wakefields Acceleration and deceleration of trapped e + /e - Power-law (n~2) spectrum of stochastic acceleration

23. 2. Relativistic Jet Dynamics Experiments Simulations of shock waves induced by jet-plasma interaction (K. Nishikawa, 02) Laboratory experiment with e + e - plasma (J. S.T. Ng)

24. LABORATORY STUDIES OF THE UNIVERSE - Probing Fundamental Physics - 1. Event Horizon Experiment (Chen and Tajima, 99)

25. A Conceptual Design of an Experiment for Detecting the Unruh Effect

26. 2. Probing Spacetime Granularity - Brownian motion: microscopic discrete nature of atom revealed in macro-structure fluctuations (Einstein, 1905) - Planck-scale spacetime fluctuations induces stochastic phase shifts of decoherent atomic wavefunction (Power and Percival, 00) A possible expt., R. Bingham, et al. (Rutherford Appleton Lab, 03)

27. SUMMARY History has shown that symbiosis between direct observation and laboratory investigation instrumental in the progress of astrophysics. Particle astrophysics and cosmology, an overlapping frontier between astrophysics and particle physics, faces deep and exciting fundamental issues for the new century. Many of these issues further overlap with high energy-density physics. Laser and particle beams are powerful tools for LabAstro. Three categories of LabAstro: Calibration of observation; Investigation of dynamics; and Probing fundamental physics; Each provides different value to astrophysics.