890 research outputs found
Constraining the mass density of free-floating black holes using razor-thin lensing arcs
Strong lensing of active galactic nuclei in the radio can result in
razor-thin arcs, with a thickness of less than a milli-arcsecond, if observed
at the resolution achievable with very long baseline interferometry (VLBI).
Such razor-thin arcs provide a unique window on the coarseness of the matter
distribution between source and observer. In this paper, we investigate to what
extent such razor-thin arcs can constrain the number density and mass function
of `free-floating' black holes, defined as black holes that do not, or no
longer, reside at the centre of a galaxy. These can be either primordial in
origin or arise as by-products of the evolution of super-massive black holes in
galactic nuclei. When sufficiently close to the line of sight, free-floating
black holes cause kink-like distortions in the arcs, which are detectable by
eye in the VLBI images as long as the black hole mass exceeds Solar
masses. Using a crude estimate for the detectability of such distortions, we
analytically compute constraints on the matter density of free-floating black
holes resulting from null-detections of distortions along a realistic, fiducial
arc, and find them to be comparable to those from quasar milli-lensing. We also
use predictions from a large hydrodynamical simulation for the demographics of
free-floating black holes that are not primordial in origin, and show that
their predicted mass density is roughly four orders of magnitude below the
constraints achievable with a single razor-thin arc.Comment: 17 pages, 13 figures, 1 table, comments welcom
Escape rate from a metastable state weakly interacting with a heat bath driven by an external noise
Based on a system-reservoir model, where the reservoir is driven by an
external stationary, Gaussian noise with arbitrary decaying correlation
function, we study the escape rate from a metastable state in the energy
diffusion regime. For the open system we derive the Fokker-Planck equation in
the energy space and subsequently calculate the generalized non-Markovian
escape rate from a metastable well in the energy diffusion domain. By
considering the dynamics in a model cubic potential we show that the results
obtained from numerical simulation are in good agreement with the theoretical
prediction. It has been also shown numerically that the well known turnover
feature can be restored from our model.Comment: 11 pages, 2 figure
Exotic phases in compact stars
We discuss how the co-existence of hyperons, antikaon condensate and color
superconducting quark matter in neutron star interior influences the gross
properties of compact stars such as, the equation of state and mass-radius
relationship. We compare our results with the recent observations. We also
discuss about superdense stars in the third family branch which may contain a
pure color-flavor-locked (CFL) core.Comment: 6 pages, presented in "Strange Quarks in Matter" (SQM2003)
conference, Atlantic Beach, NC, USA, March 12-17, 2003 and to be published in
J. Phys.
The noise properties of stochastic processes and entropy production
Based on a Fokker-Planck description of external Ornstein-Uhlenbeck noise and
cross-correlated noise processes driving a dynamical system we examine the
interplay of the properties of noise processes and the dissipative
characteristic of the dynamical system in the steady state entropy production
and flux. Our analysis is illustrated with appropriate examples.Comment: RevTex, 1 figure, To appear in Phys. Rev.
Practical Low Data-Complexity Subspace-Trail Cryptanalysis of Round-Reduced PRINCE
Subspace trail cryptanalysis is a very recent new cryptanalysis
technique, and includes differential, truncated differential,
impossible differential, and integral attacks as special cases.
In this paper, we consider PRINCE, a widely analyzed block cipher
proposed in 2012.
After the identification of a 2.5 rounds subspace trail of PRINCE, we
present several (truncated differential) attacks up to 6 rounds of PRINCE. This includes a very practical attack with the lowest data complexity of only 8 plaintexts for 4 rounds, which co-won the final round of the PRINCE challenge in the 4-round chosen-plaintext category.
The attacks have been verified using a C implementation.
Of independent interest, we consider a variant of PRINCE in which ShiftRows and MixLayer operations are exchanged in position. In particular, our result shows that the position of ShiftRows and MixLayer operations influences the security of PRINCE.
The same analysis applies to follow-up designs inspired by PRINCE
Artificial Emotion Generation Based on Personality, Mood, and Emotion for Life-Like Facial Expressions of Robots
International audienceWe can't overemphasize the importance of robot's emotional expressions as robots step into human's daily lives. So, the believable and socially acceptable emotional expressions of robots are essential. For such human-like emotional expression, we have proposed an emotion generation model considering personality, mood and history of robot's emotion. The personality module is based on the Big Five Model (OCEAN Model, Five Factor Model); the mood module has one dimension such as good or bad, and the emotion module uses the six basic emotions as defined by Ekman. Unlike most of the previous studies, the proposed emotion generation model was integrated with the Linear Dynamic Affect Expression Model (LDAEM), which is an emotional expression model that can make facial expressions similar to those of humans. So, both the emotional state and expression of robots can be changed dynamically
Density dependent hadron field theory for neutron stars with antikaon condensates
We investigate and condensation in -equilibrated
hyperonic matter within a density dependent hadron field theoretical model. In
this model, baryon-baryon and (anti)kaon-baryon interactions are mediated by
the exchange of mesons. Density dependent meson-baryon coupling constants are
obtained from microscopic Dirac Brueckner calculations using Groningen and Bonn
A nucleon-nucleon potential. It is found that the threshold of antikaon
condensation is not only sensitive to the equation of state but also to
antikaon optical potential depth. Only for large values of antikaon optical
potential depth, condensation sets in even in the presence of negatively
charged hyperons. The threshold of condensation is always reached
after condensation. Antikaon condensation makes the equation of state
softer thus resulting in smaller maximum mass stars compared with the case
without any condensate.Comment: 20 pages, 7 figures; final version to appear in Physical Review
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Highly efficient separation of actinides from lanthanides by a phenanthroline-derived bis-triazine ligand
The synthesis, lanthanide complexation, and solvent ex- traction of actinide(III) and lanthanide(III) radiotracers from nitric acid solutions by a phenanthroline-derived quadridentate bis-triazine ligand are described. The ligand separates Am(III) and Cm(III) from the lanthanides with remarkably high efficiency, high selectivity, and fast extraction kinetics compared to its 2,2'-bipyridine counterpart. Structures of the 1:2 bis-complexes of the ligand with Eu(III) and Yb(III) were elucidated by X-ray crystallography and force field calculations, respec-tively. The Eu(III) bis-complex is the first 1:2 bis-complex of a quadridentate bis-triazine ligand to be characterized by crystallography. The faster rates of extraction were verified by kinetics measurements using the rotating membrane cell technique in several diluents. The improved kinetics of metal ion extraction are related to the higher surface activity of the ligand at the phase interface. The improvement in the ligand's properties on replacing the bipyridine unit with a phenanthroline unit far exceeds what was anticipated based on ligand design alone
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