CENTRAL OBJECTIVES: THIS PROPOSAL WILL FOCUS ON THE TANTALIZING POSSIBILITY THAT THE STANDARD LAMBDA-COLD DARK MATTER (LCDM) MODEL MIGHT ONLY CONSTITUTE THE SIMPLEST APPROXIMATION TO A DARK SECTOR ENDOWED WITH A MUCH RICHER STRUCTURE. THIS IS MOTIVATED IN PART BY SOME LONGSTANDING ISSUES WITH THE LCDM MODEL ON SMALL (GALACTIC) SCALES THE LACK OF EXPERIMENTAL SUCCESS AT DETECTING WIMPS AS WELL AS THE MILD YET PERSISTENT TENSIONS BETWEEN PLANCK DATA AND LARGE-SCALE STRUCTURE SURVEYS. A SEPARATE MOTIVATION IS THE EXCITING NEW WINDOW INTO THE UNIVERSE AND THE DARK SECTOR OFFERED BY HE RECENT LIGO DISCOVERY OF GRAVITATIONAL WAVES. WE PROPOSE TO DEVELOP NOVEL THEORETICAL APPROACHES TO THE NATURE OF DARK MATTER AND DARK ENERGY AND IN CONJUNCTION NEW OBSERVATIONAL TESTS WHERE A RICHER DARK SECTOR MIGHT REVEAL ITSELF. OUR EFFORT FOCUSES SPECIFICALLY ON THE ROLE OF GRAVITY IN SUCH MODELS (AS OPPOSED TO PARTICLE PHYSICS) AND THE CONNECTIONS BETWEEN THE PROPOSED THEORIES AND THE VAST EXPERIMENTAL PROGRAM OF TESTING GRAVITY AND THE EQUIVALENCE PRINCIPLE FROM TABLE-TOP SEARCHES FOR FIFTH FORCES TO POST-NEWTONIAN MEASUREMENTS IN THE SOLAR SYSTEM TO GRAVITATIONAL WAVES FROM ASTROPHYSICAL MERGERS. OUR RESEARCH OBJECTIVES HAVE THREE BROAD DIRECTIONS: IN THE FIRST PART WE PROPOSE TO EXPLORE SEVERAL DIFFERENT TYPES OF NON-TRIVIAL STRUCTURE THAT MAY ARISE IN THE DARK SECTOR AND HOW EACH MAY BE TESTED WITH COSMOLOGICAL/ASTROPHYSICAL OBSERVATIONS. THE THEORIES OF INTEREST INCLUDE NEW MODELS OF COUPLED DM AND DE DARK SECTORS WITH ADDITIONAL DEGREES OF FREEDOM THAT MEDIATE LONG-RANGE FORCES AND NEW FORMS OF DM MOTIVATED BY CONDENSED MATTER SYSTEMS. IN THE SECOND PART WE PROPOSE NOVEL ASTROPHYSICAL TESTS OF NEW PHYSICS IN THE DARK SECTOR FOCUSING ON THE SMALLER SCALES OF GALAXIES CLUSTERS AND VOIDS. WE ALSO EXPLORE NOVEL TESTS OF SCREENING MECHANISMS IN THE SOLAR SYSTEM USING PLANETARY RINGS AND BINARY ASTEROIDS. THE THIRD PART FOCUSES ON THE EXCITING OBSERVATIONAL WINDOW OPENED UP BY THE RECENT DISCOVERY OF GRAVITATIONAL WAVES BY LIGO. IN PARTICULAR WE CONSIDER THE TANTALIZING PROSPECT OF USING GRAVITATIONAL WAVE ASTRONOMY TO TEST THEORIES OF THE DARK SECTOR IN THE STRONG GRAVITY REGIME AND THE POTENTIALLY POWERFUL CONSTRAINING POWER OF UNUSUAL EVENTS. METHODS/TECHNIQUES: OUR COLLABORATION BRINGS TOGETHER EXPERTISE RANGING FROM CONSTRUCTING WELL-MOTIVATED AND PHENOMENOLOGICALLY VIABLE THEORIES OF THE DARK SECTOR TO EXTRACTING SPECIFIC OBSERVATIONAL PREDICTIONS IN BOTH STRONG AND WEAK GRAVITY REGIMES TO EXPLOITING CURRENT AND UPCOMING SURVEY DATA TO TEST THESE PREDICTIONS TO STUDIES OF GRAVITATIONAL WAVE SOURCES. THE PROPOSED RESEARCH WILL BE PART OF A HIGHLY PRODUCTIVE COLLABORATION BETWEEN THE PI AND CO-I'S AT U. PENN AND THEIR POSTDOCS AND STUDENTS WITHIN PENN'S CENTER FOR PARTICLE COSMOLOGY. SIGNIFICANCE TO NASA SOLICITATION/INTERESTS: THE PROPOSED RESEARCH DIRECTLY SUPPORTS THE NASA ROSES SCIENCE GOAL FOR ASTROPHYSICS: TO "DISCOVER HOW THE UNIVERSE WORKS EXPLORE HOW THE UNIVERSE BEGAN AND EVOLVED''. SPECIFICALLY IT ADDRESSES THE QUESTION "HOW DO MATTER ENERGY SPACE AND TIME BEHAVE UNDER THE EXTRAORDINARILY DIVERSE CONDITIONS OF THE COSMOS?'' AND SCIENCE OBJECTIVE TO "UNDERSTAND THE ORIGIN AND DESTINY OF THE UNIVERSE AND THE NATURE OF BLACK HOLES DARK ENERGY DARK MATTER AND GRAVITY''. THE PROPOSAL WILL INCLUDE NOVEL APPLICATIONS OF SOLAR SYSTEM DYNAMICAL DATA FROM THE CASSINI-HUYGENS AND THE WIDE INFRARED SURVEY EXPLORER (WISE) MISSIONS AS A RICH TEST OF DARK SECTOR PHYSICS THROUGH PLANETARY RING AND BINARY ASTEROID DYNAMICS RESPECTIVELY. THE PROPOSAL WILL ALSO IN AN INTEGRATED FASHION LAY IMPORTANT THEORETICAL GROUNDWORK FOR HOW DATA FROM THE NASCENT EPOCH OF GRAVITATIONAL WAVE ASTRONOMY CAN CONSTRAIN AND PROVIDE INSIGHT INTO PHYSICS BEYOND THE STANDARD COSMOLOGICAL MODEL.