No abstract

In this work we introduce the Alcubierre warp metric using spherical symmetry. In this way we write the Einstein equations for a perfect fluid and for an anisotropic fluid with cosmological constant. Analysing the energy conditions for both cases, we find that these cases are flexible enough to allow them to be satisfied. We also find that in the time-independent case of the warp bubble, the metric admits a timelike Killing vector and all the energy conditions are satisfied except for the strong energy condition. Moreover, in the time-independent case a barotropic equation of state known from cosmological models naturally arises.

One of the biggest hurdles nowadays rocket propulsion is the large use of fuel. The amount of fuel and the burning efficiency defines how long the rocket engine can work which intimately limits the range and the load capacity of the rockets and spaceships. This according to the Newton third law is unavoidable - in order to move forward you need to leave something behind. There have been several attempts in the past to create an engine which doesn't use fuel in the common sense, like the M drive, but so far all of them were unsuccessful. In this article we attempt to explore a novel principle, a recycling cycle of fuel, by optimizing parametrically a system that uses ?He phase transition.

In nature all of the heavy elements are produced by nuclear fusion reactions, mostly in supernova explosions and neutron star collisions, so, this is to date the only known and proven mechanism to produce heavy elements in usable quantities. In this work we approach a difficult challenge, namely, the possibility of fusion of heavy elements, taking as a test case the heaviest observationally stable element - ²³?U, showing that it is feasible, at least in principle with the help of existing technologies. The main idea behind is to show that fusion of lighter - than z=184 - nuclei is conceptually viable examining the tunnel effect assisted by an auxiliary field that will produce a Sauter like effect, and this is the pathway to explore the synthesis of elements higher than z=118. The production of theoretical untested elements like Unoctquadium-184 or close Z species could open a new chapter in the physics of super-heavy elements, and leads to a deeper understanding of nuclear decay channels and stability conditions. Nuclear fusion of heavy elements will open the breach to produce neutron rich elements, so we may obtain a deep insight into the physics of the island of stability. This work will review basic aspects of fusion physics related to the assisted fusion mechanism. An enhanced fusion perspective is found generalizing the work of [1] to space dependent fields and the cases of ²H, ¹??Pd and ²³?U are presented for several test fields. A final section reviewing laser confinement fusion actual experiments capable of achieving the required energies is also reported.