12,675 research outputs found
An M-theory solution generating technique and SL(2,R)
In this paper we generalize the O(p+1,p+1) solution generating technique
(this is a method used to deform Dp-branes by turning on a NS-NS B-field) to
M-theory, in order to be able to deform M5-brane supergravity solutions
directly in eleven dimensions, by turning on a non zero three form A. We find
that deforming the M5-brane, in some cases, corresponds to performing certain
SL(2,R) transformations of the Kahler structure parameter for the three-torus,
on which the M5-brane has been compactified. We show that this new M-theory
solution generating technique can be reduced to the O(p+1,p+1) solution
generating technique with p=4. Further, we find that it implies that the open
membrane metric and generalized noncommutativity parameter are manifestly
deformation independent for electric and light-like deformations. We also
generalize the O(p+1,p+1) method to the type IIA/B NS5-brane in order to be
able to deform NS5-branes with RR three and two forms, respectively. In the
type IIA case we use the newly obtained solution generating technique and
deformation independence to derive a covariant expression for an open D2-brane
coupling, relevant for OD2-theory.Comment: 24 pages, Latex. v2:Sections 3.2 and 3.3 improved. v3:Some
clarifications added. Version published in JHE
Parity independence of the zero-bias conductance peak in a nanowire based topological superconductor-quantum dot hybrid device
We explore the signatures of Majorana fermions in a nanowire based
topological superconductor-quantum dot-topological superconductor hybrid device
by charge transport measurements. The device is made from an epitaxially grown
InSb nanowire with two superconductor Nb contacts on a Si/SiO substrate. At
low temperatures, a quantum dot is formed in the segment of the InSb nanowire
between the two Nb contacts and the two Nb contacted segments of the InSb
nanowire show superconductivity due to the proximity effect. At zero magnetic
field, well defined Coulomb diamonds and the Kondo effect are observed in the
charge stability diagram measurements in the Coulomb blockade regime of the
quantum dot. Under the application of a finite, sufficiently strong magnetic
field, a zero-bias conductance peak structure is observed in the same Coulomb
blockade regime. It is found that the zero-bias conductance peak is present in
many consecutive Coulomb diamonds, irrespective of the even-odd parity of the
quasi-particle occupation number in the quantum dot. In addition, we find that
the zero-bias conductance peak is in most cases accompanied by two differential
conductance peaks, forming a triple-peak structure, and the separation between
the two side peaks in bias voltage shows oscillations closely correlated to the
background Coulomb conductance oscillations of the device. The observed
zero-bias conductance peak and the associated triple-peak structure are in line
with the signatures of Majorana fermion physics in a nanowire based topological
superconductor-quantum dot-topological superconductor system, in which the two
Majorana bound states adjacent to the quantum dot are hybridized into a pair of
quasi-particle states with finite energies and the other two Majorana bound
states remain as the zero-energy modes located at the two ends of the entire
InSb nanowire.Comment: 6 pages, 4 figure
Visualization, Exploration and Data Analysis of Complex Astrophysical Data
In this paper we show how advanced visualization tools can help the
researcher in investigating and extracting information from data. The focus is
on VisIVO, a novel open source graphics application, which blends high
performance multidimensional visualization techniques and up-to-date
technologies to cooperate with other applications and to access remote,
distributed data archives. VisIVO supports the standards defined by the
International Virtual Observatory Alliance in order to make it interoperable
with VO data repositories. The paper describes the basic technical details and
features of the software and it dedicates a large section to show how VisIVO
can be used in several scientific cases.Comment: 32 pages, 15 figures, accepted by PAS
Extremely narrow spectrum of GRB110920A: further evidence for localised, subphotospheric dissipation
Much evidence points towards that the photosphere in the relativistic outflow
in GRBs plays an important role in shaping the observed MeV spectrum. However,
it is unclear whether the spectrum is fully produced by the photosphere or
whether a substantial part of the spectrum is added by processes far above the
photosphere. Here we make a detailed study of the ray emission from
single pulse GRB110920A which has a spectrum that becomes extremely narrow
towards the end of the burst. We show that the emission can be interpreted as
Comptonisation of thermal photons by cold electrons in an unmagnetised outflow
at an optical depth of . The electrons receive their energy by a
local dissipation occurring close to the saturation radius. The main spectral
component of GRB110920A and its evolution is thus, in this interpretation,
fully explained by the emission from the photosphere including localised
dissipation at high optical depths.Comment: 14 pages, 11 figures, accepted to MNRA
A low-frequency study of recently identified double-double radio galaxies
In order to understand the possible mechanisms of recurrent jet activity in
radio galaxies and quasars, which are still unclear, we have identified such
sources with a large range of linear sizes (220 917 kpc), and hence time
scales of episodic activity. Here we present high-sensitivity 607-MHz Giant
Metrewave Radio Telescope (GMRT) images of 21 possible double-double radio
galaxies (DDRGs) identified from the FIRST survey to confirm their episodic
nature. These GMRT observations show that none of the inner compact components
suspected to be hot-spots of the inner doubles are cores having a flat radio
spectrum, confirming the episodic nature of these radio sources. We have
indentified a new DDRG with a candidate quasar, and have estimated the upper
spectral age limits for eight sources which showed marginal evidence of
steepening at higher frequencies. The estimated age limits (11 52 Myr) are
smaller than those of the large-sized ( 1 Mpc) DDRGs.Comment: Accepted for publication in MNRAS. 14 pages, 7 figure
The Electrostatic Ion Beam Trap : a mass spectrometer of infinite mass range
We study the ions dynamics inside an Electrostatic Ion Beam Trap (EIBT) and
show that the stability of the trapping is ruled by a Hill's equation. This
unexpectedly demonstrates that an EIBT, in the reference frame of the ions
works very similar to a quadrupole trap. The parallelism between these two
kinds of traps is illustrated by comparing experimental and theoretical
stability diagrams of the EIBT. The main difference with quadrupole traps is
that the stability depends only on the ratio of the acceleration and trapping
electrostatic potentials, not on the mass nor the charge of the ions. All kinds
of ions can be trapped simultaneously and since parametric resonances are
proportional to the square root of the charge/mass ratio the EIBT can be used
as a mass spectrometer of infinite mass range
Contextualized behavior for improving managerial and entrepreneurial decision-making
Since the conceptualization of bounded rationality by Herbert Simon (1947), management scholars started investigating how people—managers and entrepreneurs—really
make decisions within (and for) organizations. Taking into considerations the effect on
organizational choices (e.g., new product development, market entry, merger and/or acquisition of other entities) and related performance (in organizational, economic, and social
terms), a series of trends have flourished within this pivotal research area. Nowadays, the
main important are: the biasing or beneficial role of heuristics (i.e., cognitive shortcuts of
human mind) (Kahneman 2003), the influence of socio-demographic characteristics and
personality traits (see the derived Upper Echelons Theory; Hambrick and Mason 1984;
Abatecola and Cristofaro 2020), the impact of affective states (e.g., emotions, mood, temperament), the intertwinement between cognitive and emotional factors, the co-determinant
role of the (micro-, meso-, and macro-) environment in the formation of choices with
person-, group-, firm-specific variables, and the biasing or beneficial impact of technologies
on managers’ and entrepreneurs’ rationality.info:eu-repo/semantics/publishedVersio
Hom-Lie color algebra structures
This paper introduces the notion of Hom-Lie color algebra, which is a natural
general- ization of Hom-Lie (super)algebras. Hom-Lie color algebras include
also as special cases Lie (super) algebras and Lie color algebras. We study the
homomorphism relation of Hom-Lie color algebras, and construct new algebras of
such kind by a \sigma-twist. Hom-Lie color admissible algebras are also defined
and investigated. They are finally classified via G-Hom-associative color
algebras, where G is a subgroup of the symmetric group S_3.Comment: 16 page
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