6,902 research outputs found
Constraints on a strong X-ray flare in the Seyfert galaxy MCG-6-30-15
We discuss implications of a strong flare event observed in the Seyfert
galaxy MCG-6-30-15 assuming that the emission is due to localized magnetic
reconnection. We conduct detailed radiative transfer modeling of the
reprocessed radiation for a primary source that is elevated above the disk. The
model includes relativistic effects and Keplerian motion around the black hole.
We show that for such a model setup the observed time-modulation must be
intrinsic to the primary source. Using a simple analytical model we then
investigate time delays between hard and soft X-rays during the flare. The
model considers an intrinsic delay between primary and reprocessed radiation,
which measures the geometrical distance of the flare source to the reprocessing
sites. The observed time delays are well reproduced if one assumes that the
reprocessing happens in magnetically confined, cold clouds.Comment: 4 pages, 2 figures, proceedings of a talk given at the symposium 238
at the IAU General Assembly 200
The projective translation equation and unramified 2-dimensional flows with rational vector fields
Let X=(x,y). Previously we have found all rational solutions of the
2-dimensional projective translation equation, or PrTE,
(1-z)f(X)=f(f(Xz)(1-z)/z); here f(X)=(u(x,y),v(x,y)) is a pair of two (real or
complex) functions. Solutions of this functional equation are called projective
flows. A vector field of a rational flow is a pair of 2-homogenic rational
functions. On the other hand, only special pairs of 2-homogenic rational
functions give rise to rational flows. In this paper we are interested in all
non-singular (satisfying the boundary condition) and unramified (without
branching points, i.e. single-valued functions in C^2\{union of curves})
projective flows whose vector field is still rational. We prove that, up to
conjugation with 1-homogenic birational plane transformation, these are of 6
types: 1) the identity flow; 2) one flow for each non-negative integer N -
these flows are rational of level N; 3) the level 1 exponential flow, which is
also conjugate to the level 1 tangent flow; 4) the level 3 flow expressable in
terms of Dixonian (equianharmonic) elliptic functions; 5) the level 4 flow
expressable in terms of lemniscatic elliptic functions; 6) the level 6 flow
expressable in terms of Dixonian elliptic functions again. This reveals another
aspect of the PrTE: in the latter four cases this equation is equivalent and
provides a uniform framework to addition formulas for exponential, tangent, or
special elliptic functions (also addition formulas for polynomials and the
logarithm, though the latter appears only in branched flows). Moreover, the
PrTE turns out to have a connection with Polya-Eggenberger urn models. Another
purpose of this study is expository, and we provide the list of open problems
and directions in the theory of PrTE; for example, we define the notion of
quasi-rational projective flows which includes curves of arbitrary genus.Comment: 34 pages, 2 figure
DPA on quasi delay insensitive asynchronous circuits: formalization and improvement
The purpose of this paper is to formally specify a flow devoted to the design
of Differential Power Analysis (DPA) resistant QDI asynchronous circuits. The
paper first proposes a formal modeling of the electrical signature of QDI
asynchronous circuits. The DPA is then applied to the formal model in order to
identify the source of leakage of this type of circuits. Finally, a complete
design flow is specified to minimize the information leakage. The relevancy and
efficiency of the approach is demonstrated using the design of an AES
crypto-processor.Comment: Submitted on behalf of EDAA (http://www.edaa.com/
Global fit to Higgs signal strengths and couplings and implications for extended Higgs sectors
The most recent LHC data have provided a considerable improvement in the
precision with which various Higgs production and decay channels have been
measured. Using all available public results from ATLAS, CMS and the Tevatron,
we derive for each final state the combined confidence level contours for the
signal strengths in the (gluon fusion + ttH associated production) versus
(vector boson fusion + VH associated production) space. These "combined signal
strength ellipses" can be used in a simple, generic way to constrain a very
wide class of New Physics models in which the couplings of the Higgs boson
deviate from the Standard Model prediction. Here, we use them to constrain the
reduced couplings of the Higgs boson to up-quarks, down-quarks/leptons and
vector boson pairs. We also consider New Physics contributions to the
loop-induced gluon-gluon and photon-photon couplings of the Higgs, as well as
invisible/unseen decays. Finally, we apply our fits to some simple models with
an extended Higgs sector, in particular to Two-Higgs-Doublet models of Type I
and Type II, the Inert Doublet model, and the Georgi-Machacek triplet Higgs
model.Comment: 31 pages, 15 figures; v2: fixed important factor of 2 missing in Eq.
(1) (results unchanged), extended discussion in the next-to-last paragraph of
Section 3, some references added; v3: appendices and references added,
matches version accepted by PR
Status of invisible Higgs decays
We analyze the extent to which the LHC and Tevatron results as of the end of
2012 constrain invisible (or undetected) decays of the Higgs boson-like state
at ~ 125 GeV. To this end we perform global fits for several cases: 1) a Higgs
boson with Standard Model (SM) couplings but additional invisible decay modes;
2) SM couplings to fermions and vector bosons, but allowing for additional new
particles modifying the effective Higgs couplings to gluons and photons; 3) no
new particles in the loops but tree-level Higgs couplings to the up-quarks,
down-quarks and vector bosons, relative to the SM, treated as free parameters.
We find that in the three cases invisible decay rates of 23%, 61%, 88%,
respectively, are consistent with current data at 95% confidence level (CL).
Limiting the coupling to vector bosons, CV, to CV < 1 in case 3) reduces the
allowed invisible branching ratio to 56% at 95% CL. Requiring in addition that
the Higgs couplings to quarks have the same sign as in the SM, an invisible
rate of up to 36% is allowed at 95% CL. We also discuss direct probes of
invisible Higgs decays, as well as the interplay with dark matter searches.Comment: 14 pages, 8 figures; v2: extended discussion on ZH associated
production, references added, minor corrections; v4: matches final version
published in Phys. Lett.
Higgs Couplings at the End of 2012
Performing a fit to all publicly available data, we analyze the extent to
which the latest results from the LHC and Tevatron constrain the couplings of
the Higgs boson-like state at ~ 125 GeV. To this end we assume that only
Standard Model (SM) particles appear in the Higgs decays, but tree-level Higgs
couplings to the up-quarks, down-quarks and vector bosons, relative to the SM
are free parameters. We also assume that the leptonic couplings relative to the
SM are the same as for the down-quark, and a custodial symmetry for the V=W,Z
couplings. In the simplest approach, the effective Higgs couplings to gluons
and photons are computed in terms of the previous parameters. This approach is
also applied to Two-Higgs-Doublet Models of Type I and Type II. However, we
also explore the possibility that the net Higgs to gluon-gluon and gamma-gamma
couplings have extra loop contributions coming from Beyond-the-Standard Model
physics. We find that the SM p-value ~ 0.5 is more than 2 sigma away from fits
in which: a) there is some non-SM contribution to the gamma-gamma coupling of
the Higgs; or b) the sign of the top quark coupling to the Higgs is opposite
that of the W coupling. In both these cases p-values ~ 0.9 can be achieved.
Since option b) is difficult to realize in realistic models, it would seem that
new physics contributions to the effective couplings of the Higgs are
preferred.Comment: 25 pages, 11 figures; v2: minor corrections, references added; v3:
acknowledgement adde
2012 NASA Range Safety Annual Report
This report provides a NASA Range Safety (NRS) overview for current and potential range users. This report contains articles which cover a variety of subject areas, summaries of various NASA Range Safety Program (RSP) activities performed during the past year, links to past reports, and information on several projects that may have a profound impact on the way business will be conducted in the future. Specific topics discussed in the 2012 NASA Range Safety Annual Report include a program overview and 2012 highlights; Range Safety Training; Independent Assessments; Support to Program Operations at all ranges conducting NASA launch/flight operations; a continuing overview of emerging range safety-related technologies; and status reports from all of the NASA Centers that have Range Safety responsibilities
Towards a public analysis database for LHC new physics searches using MadAnalysis 5
We present the implementation, in the MadAnalysis 5 framework, of several
ATLAS and CMS searches for supersymmetry in data recorded during the first run
of the LHC. We provide extensive details on the validation of our
implementations and propose to create a public analysis database within this
framework.Comment: 20 pages, 15 figures, 5 recast codes; version accepted by EPJC (Dec
22, 2014) including a new section with guidelines for the experimental
collaborations as well as for potential contributors to the PAD;
complementary information can be found at
http://madanalysis.irmp.ucl.ac.be/wiki/PhysicsAnalysisDatabas
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