arXiv subjects

S. V. Krasnikov

Publications and source records attributed to S. V. Krasnikov.

7 recordsLinked to original sources

arXiv2020

Search for wormhole candidates in active galactic nuclei: radiation from colliding accreting flows

The underlying hypothesis of this work is that the active galactic nuclei (AGNs) are wormhole mouths rather than supermassive black holes (SMBHs). Under some - quite general - assumptions such wormholes may emit gamma radiation as a result of a collision of accreting flows inside the wormholes. This radiation has a distinctive spectrum much different from those of jets or accretion disks of AGNs. An observation of such radiation would serve as evidence of the existence of wormholes.

astro-ph.HE↗

arXiv2009

Gravitational strings. Do we see one?

I present a class of objects called gravitational strings (GS) for their similarity to the conventional cosmic strings: even though the former are just singularities in flat spacetime, both varieties are equally "realistic", they may play equally important cosmological rôle and their lensing properties are akin. I argue that the enigmatic object CSL-1 is an evidence in favor of the existence of GS.

gr-qc↗

arXiv2000

Toward a Traversable Wormhole

In this talk I discuss pertinence of the wormholes to the problem of circumventing the light speed barrier and present a specific class of wormholes. The wormholes of this class are static and have arbitrarily wide throats, which makes them traversable. The matter necessary for these spacetimes to be solutions of the Einstein equations is shown to consist of two components, one of which satisfies the Weak energy condition and the other is produced by vacuum fluctuations of neutrino, electromagnetic (in dimensional regularization), and/or massless scalar (conformally coupled) fields.

gr-qc↗

arXiv1998

A singularity-free WEC-respecting time machine

A time machine (TM) is constructed whose creating in contrast to all TMs known so far requires neither singularities, nor violation of the weak energy condition (WEC). The spacetime exterior to the TM closely resembles the Friedmann universe.

gr-qc↗

arXiv1998

Hyperfast Interstellar Travel in General Relativity

The problem is discussed of whether a traveller can reach a remote object and return back sooner than a photon would when taken into account that the traveller can partly control the geometry of his world. It is argued that under some reasonable assumptions in globally hyperbolic spacetimes the traveller cannot hasten reaching the destination. Nevertheless, it is perhaps possible for him to make an arbitrarily long round-trip within an arbitrarily short (from the point of view of a terrestrial observer) time.

gr-qc↗

arXiv1997

Time Machines with Non-compactly Generated Cauchy Horizons and ``Handy Singularities"

The use of "handy singularities" (i.e. singularities similar to those arising in the Deutch-Politzer space) enables one to avoid (almost) all known difficulties inherent usually to creation of time machines. A simple method is discussed for constructing a variety of such singularities. A few 3-dimensional examples are cited.

gr-qc↗

arXiv1995

On the Quantum Stability of the Time Machine

In a number of papers it has been claimed that the time machine are quantum unstable, which manifests itself in the divergence of the vacuum expectation value of the stress-energy tensor $\langle{\bf T}\rangle$ near the Cauchy horizon. The expression for $\langle{\bf T}\rangle$ was found in these papers on the basis of some specific approach \cite{Fro,KimT}.\par We show that this approach is untenable in that the above expression firstly is not derived from some more fundamental and undeniable premises, as it is claimed, but rather postulated and secondly contains undefined terms, so that one can neither use nor check it. As a counterexample we cite a few cases of (two-dimensional) spacetimes containing time machines with $\langle{\bf T}\rangle$ bounded near the Cauchy horizon.

gr-qc↗