CORNELL UNIVERSITY WILL CARRY OUT THEORETICAL AND EXPERIMENTAL EFFORTS ON CRITICAL ISSUES RELATED TO SUPER-PONDEROMOTIVE EFFECTS DURING THE STRONGLY NONLINEAR (NON-PERTURBATIVE) INTERACTION OF ULTRA-INTENSE LASER PULSES WITH UNDER-DENSE PLASMAS IN THE RELATIVISTIC REGIME. ALTHOUGH THE EMPHASIS OF THEIR PROPOSED RESEARCH IS ON UNCOVERING NEW FUNDAMENTAL EFFECTS IN RELATIVISTIC LASER-PLASMA INTERACTION, SPECIAL EMPHASIS WILL BE ON PROPOSING AND EXPLORING NOVEL LASER-PLASMA SCENARIOS THAT CAN BE EXPERIMENTALLY REALIZED USING THE LWFA-BASED X-RAY BEAM-LINE AT THE ADVANCED LASER LIGHT SOURCE (ALLS): AN IMPORTANT COMPONENT OF THE LASERNETUS, WHICH IS CLOSE GEOGRAPHIC PROXIMITY (I.E. WITHIN DRIVING DISTANCE) TO CORNELL. ALLS FACILITY HAS THE UNIQUE CAPABILITY OF PRODUCING > 100 TW PEAK-POWER ULTRA-SHORT (OF ORDER 20 FS) LASER PULSES FOCUSED TO A SMALL SPOT, THEREBY ENABLING THE A_L»1 REGIME THAT IS REQUIRED FOR OBSERVING SUPER-PONDEROMOTIVE PHENOMENA. THE SHORT DURATION OF THE LASER PULSE WOULD ENABLE THE OBSERVATION OF INHERENTLY PHASE- AND POLARIZATION-DEPENDENT PHENOMENA ASSOCIATED WITH THE SUPER-PONDEROMOTIVE REGIME OF LASER-PLASMA INTERACTIONS.