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The radiative cooling of electrons responsible for the nonthermal synchrotron emission of large scale jets of radiogalaxies and quasars requires quasi continuous (in time and space) production of relativistic electrons throughout the jets…
The Breakthrough Starshot project aims to send centimeter-sized, gram-scale "StarChip" probes to Alpha Centauri at a speed of $\sim0.2c$. On the other hand, Zhang \& Li recently proposed that trans-relativistic cameras may be sent to any…
We consider gravitational radiation in the presence of non-compact extra dimensions. If their number is odd, all spacetime becomes odd-dimensional and formation of gravitational radiation becomes non-trivial because of violation of the…
A method for asteroid deflection that makes use of a spacecraft moving back and forth on a segment of an appropriate Keplerian orbit about the asteroid is described and evaluated. It is shown that, on average, the spacecraft describing such…
Exploring and traveling to distant stars has long fascinated humanity but has been limited due to the vast distances. The Breakthrough Starshot Program aims at eliminating this limitation by traveling to Alpha Centauri, which is 4.37…
Consuming long-range interplanetary medium with fuel for driving plasma thrust is vital. Methods of capturing the space environment depending on its density and the ship velocity are indispensable issues to extract the space environment as…
We calculate the severe radiative energy losses which occur at the base of black hole jets using a relativistic fluid jet model, including in-situ acceleration of non-thermal leptons by magnetic reconnection. Our results demonstrate that…
In our previous work (Phys. Rev. Research 7, 033079), we derived the metric tensor for cylindrically shaped pulses with uniform energy density. Building upon that framework, we derive the complete set of geodesics with zero angular…
The detection and characterisation of Earth-like planets with Doppler signals of the order of 1 m/s currently represent one of the greatest challenge for extrasolar-planet hunters. As results for such findings are often controversial, it is…
Warp drives in Einstein's general theory of relativity provide a unique mechanism for manned interstellar travel. It is well-known that the classical superluminal soliton spacetimes require negative energy densities, likely sourced by…
It has been suggested that relativistic blast waves may power the jets of AGN and gamma-ray bursts (GRB). We address the important issue how the kinetic energy of collimated blast waves is converted into radiation. It is shown that swept-up…
The dependence of the cosmic ray intensity on Galactocentric distance is known to be much less rapid than that to be thought-to-be sources: supernova remnants. This is an old problem ('the radial gradient problem') which has led to a number…
Microwave propelled sails are a new class of spacecraft using photon acceleration. It is the only method of interstellar flight that has no physics issues. Laboratory demonstrations of basic features of beam-driven propulsion, flight,…
A charge-free, point particle of infinitesimal mass orbiting a Kerr black hole is known to move along a geodesic. When the particle has a finite mass or charge, it emits radiation which carries away orbital energy and angular momentum, and…
The most efficient energy sources known in the Universe are accretion disks. Those around black holes convert 5 -- 40 per cent of rest-mass energy to radiation. Like water circling a drain, inflowing mass must lose angular momentum,…
Cosmic ray (CR) transport and acceleration is determined by the properties of magnetic turbulence. Recent advances in MHD turbulence call for revisions in the paradigm of cosmic ray transport. We use the models of magnetohydrodynamic…
An electron irradiated by a linearly polarized relativistic intensity laser pulse in a cylindrical plasma channel can gain significant energy from the pulse. The laser electric and magnetic fields drive electron oscillations in a plane…
Experience in exploring our own solar system has shown that direct investigation of planetary bodies using space probes invariably yields scientific knowledge not otherwise obtainable. In the case of exoplanets, such direct investigation…
The question of the collimation of relativistic jets is the subject of a lively debate in the community. We numerically compute the apparent velocity and the Doppler factor of a non homokinetic jet using different velocity profile, to study…
Angular momentum in protostellar discs can be transported either radially, through turbulence induced by the magnetorotational instability (MRI), or vertically, through the torque exerted by a large-scale magnetic field. We present a model…