We investigate whether the circum-burst environment constrained by the absorption feature of GRB990705 could be consistent with the observed H-band afterglow. Two possible geometries of the afterglow-emitting regions are suggested: 1) afterglow emission produced by the impact of the fireball on the surrounding torus; 2)afterglow emission produced in the dense circum-burst medium inside the torus. In case 1), the faster decay at later time is attributed to the disappearance of the shock due to the counter-pressure in the hot torus illuminated by the burst and afterglow photons. For case 2), the circum-burst medium density is found to be very high (n ≳ 104 − 105cm−3).

The interaction of a relativistic fireball with its ambient medium is described through two shocks: a reverse shock that propagates into the fireball, and a forward shock that propagates into the medium. We here study very early afterglows from the reverse and forward shocks in winds. An optical flash arises from both the relativistic reverse and forward shock while a radio flare is produced by the forward shock.

Recent results on neutrino masses and mixing are presented. There is convincing evidence for nonzero but tiny masses of at least two flavor neutrinos, based on two types of neutrino oscillations, solar and atmospheric neutrinos. The large mixing angle between first and second flavors and also the one between the second and third flavors were found, quite contrary to small mixing angles among quark flavors, and pose a new mystery.

This paper briefly describes the principle of operation and science goals of the AMANDA high energy neutrino telescope located at the South Pole, Antarctica. Results from an earlier phase of the telescope, called AMANDA-BIO, demonstrate both reliable operation and the broad astrophysical reach of this device, which includes searches for a variety of sources of ultrahigh energy neutrinos: generic point sources, Gamma-Ray Bursts and diffuse sources. The predicted sensitivity and angular resolution of the telescope were confirmed by studies of atmospheric muon and neutrino backgrounds. We also report on the status of the analysis from AMANDA-II, a larger version with far greater capabilities. At this stage of analysis, details of the ice properties and other systematic uncertainties of the AMANDA-II telescope are under study, but we have made progress toward critical science objectives. In particular, we present the first preliminary flux limits from AMANDA-II on the search for continuous emission from astrophysical point sources, and report on the search for correlated neutrino emission from Gamma Ray Bursts detected by BATSE before decommissioning in May 2000. During the next two years, we expect to exploit the full potential of AMANDA-II with the installation of a new data acquisition system that records full waveforms from the in-ice optical sensors.

The highest energy cosmic rays provide compelling evidence for EeV neutrino sources, if we can achieve the Teraton target volumes needed. At 10 TeV energies and above neutrino astronomy is in fact the only astronomy with a clear view of the whole universe. Radio detection of neutrino cascade interactions in ice and other solid dielectric media, via the Askaryan effect, provide a realistic path toward this goal.

An approach is used to find out the present time approximate values of the characteristic amplitudes, the spectral densities, the intensties and the frequencies of the Primordial Gravitational Waves (PmGW), in the spatially perturbed Friedman - Robertson - Walker (FRW) adiabatically expanding Universe. The temporal variation of the magnitude of the time gradient of the characteristic amplitudes of the PmGW is calculated in spatial perturbed FRW Universe. The obtained results via this non-conventional approach may be of interest to shed some light on the possibilities of searching for the PmGW at definite frequency bands by the existing and the future networks of detectors.

Sub-TeV and TeV energy gamma-ray astronomy reveals non-thermal gamma-ray pictures of our universe and serve as a probe to understand the origin, acceleration and propagation of cosmic rays. Recent status of ground-based high-energy gamma-ray astronomy is reviewed.

REM (Rapid Eye Mount) is a fully robotized fast slewing telescope equipped with a high throughput Near InfraRed (Z′, J, H, K′) camera (REMIR) and an optical slitless spectrograph (ROSS). A dedicated software for data reduction and software (AQuA) has been developed to extract scientific information from REM images without any human intervent. REM is installed in La Silla (Chile) and dedicated to detect and study the prompt optical/IR afterglow of Gamma Ray Bursts with the ambitious project of discovering objects at extremely high redshift. The synergy between REMIR camera and ROSS makes REM a powerful observing tool for any kind of fast transient phenomena.

The two instruments aboard the Gamma-Ray Large Area Space Telescope (GLAST) mission will make unprecedented spectral observations of gamma-ray bursts. I will discuss what new science we can expect from GLAST.

The existence of extremely high energy cosmic rays (EHECRs) with energy above 1020eV have been reported by several air shower experiments. The sources of these cosmic rays were considered to be extra-galactic. Relevant high energy astrophysical sources were searched in the arrival direction of these cosmic rays but no appropriate candidates were found. The origin of EHECRs stays unexplained. We review the present status of EHECR studies and introduce several new experiments aiming to unveil its mysterious origin.

The original intent of the conference was to focus, first, on the physical processes (accretion, collimation, and all the rest) shared by two or more of the kinds of sources generally thought of as belonging to high energy astrophysics and, second, on the full range of phenomena, at all wavelengths, exhibited by those sources. This summary therefore addresses some of these issues as well as some new results presented at the symposium and some of the still-unanswered questions that were raised.