7,862 research outputs found
The Structure of the Proton in the LHC Precision Era
We review recent progress in the determination of the parton distribution
functions (PDFs) of the proton, with emphasis on the applications for precision
phenomenology at the Large Hadron Collider (LHC). First of all, we introduce
the general theoretical framework underlying the global QCD analysis of the
quark and gluon internal structure of protons. We then present a detailed
overview of the hard-scattering measurements, and the corresponding theory
predictions, that are used in state-of-the-art PDF fits. We emphasize here the
role that higher-order QCD and electroweak corrections play in the description
of recent high-precision collider data. We present the methodology used to
extract PDFs in global analyses, including the PDF parametrization strategy and
the definition and propagation of PDF uncertainties. Then we review and compare
the most recent releases from the various PDF fitting collaborations,
highlighting their differences and similarities. We discuss the role that QED
corrections and photon-initiated contributions play in modern PDF analysis. We
provide representative examples of the implications of PDF fits for
high-precision LHC phenomenological applications, such as Higgs coupling
measurements and searches for high-mass New Physics resonances. We conclude
this report by discussing some selected topics relevant for the future of PDF
determinations, including the treatment of theoretical uncertainties, the
connection with lattice QCD calculations, and the role of PDFs at future
high-energy colliders beyond the LHC.Comment: 170 pages, 85 figures, version to be published in Physics Report
Topological entropy of continuous self–maps on a graph
Let G be a graph and f be a continuous self–map on G. We provide sufficient conditions based on the Lefschetz zeta function in order that f has positive topological entropy. Moreover, for the particular graphs: p–flower graph, n-lips graph and (p+r1L1+:::+rsLs)–graph we are able to go further and state more precise conditions for having positive topological entropy.The second author is partially supported by the Ministerio de EconomĂa, Industria y Competitividad, Agencia Estatal de InvestigaciĂłn grants MTM-2016-77278-P (FEDER) and MDM-2014-0445, the Agència de GestiĂł d’Ajuts Universitaris i de Recerca grant 2017SGR1617, and the H2020 European Research Council grant MSCA-RISE-2017-777911
Dense-Coding Attack on Three-Party Quantum Key Distribution Protocols
Cryptanalysis is an important branch in the study of cryptography, including
both the classical cryptography and the quantum one. In this paper we analyze
the security of two three-party quantum key distribution protocols (QKDPs)
proposed recently, and point out that they are susceptible to a simple and
effective attack, i.e. the dense-coding attack. It is shown that the
eavesdropper Eve can totally obtain the session key by sending entangled qubits
as the fake signal to Alice and performing collective measurements after
Alice's encoding. The attack process is just like a dense-coding communication
between Eve and Alice, where a special measurement basis is employed.
Furthermore, this attack does not introduce any errors to the transmitted
information and consequently will not be discovered by Alice and Bob. The
attack strategy is described in detail and a proof for its correctness is
given. At last, the root of this insecurity and a possible way to improve these
protocols are discussed.Comment: 6 pages, 3 figure
Anisotropic Magneto-conductance of InAs Nanowire: Angle Dependent Suppression of 1D Weak Localization
The magneto-conductance of an InAs nanowire is investigated with respect to
the relative orientation between external magnetic field and the nanowire axis.
It is found that both the perpendicular and the parallel magnetic fields induce
a positive magneto-conductance. Yet the parallel magnetic field induced
longitudinal magneto-conductance has a smaller magnitude. This anisotropic
magneto-transport phenomenon is studied as a function of temperature, magnetic
field strength and at an arbitrary angle between the magnetic field and the
nanowire. We show that the observed effect is in quantitative agreement with
the suppression of one-dimensional (1D) weak localization
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