33,036 research outputs found
The Pentaquarks in the Linear Molecular Heptaquark Model
In this talk, multiquarks are studied microscopically in a standard quark
model. In pure ground-state pentaquarks the short-range interaction is computed
and it is shown to be repulsive. An additional quark-antiquark pair is then
considered, and this is suggested to produce linear molecular system, with a
narrow decay width. The quarks assemble in three hadronic clusters, and the
central hadron provides stability. The possible crypto-heptaquark hadrons with
exotic pentaquark flavours, with strange, charmed and bottomed quarks, are
predicted.Comment: 6 pages, 3 tables, talk presented as the Eighth Workshop on
Non-Perturbative Quantum Chromodynamics 7-11 June 2004, Paris, proceedings
edited by B. Muller, Chung-I Tan and Y. Gabellin
Exotic pentaquarks, crypto-heptaquarks and linear three-hadronic molecules
In this talk, multiquarks are studied microscopically in a standard quark
model. In pure ground-state pentaquarks the short-range interaction is computed
and it is shown to be repulsive, a narrow pentaquark cannot be in the
groundstate. As a possible excitation, an additional quark-antiquark pair is
then considered, and this is suggested to produce linear molecular system, with
a narrow decay width. This excitation may be energetically favourable to the
p-wave excitation suggested by the other pentaquark models. Here, the quarks
assemble in three hadronic clusters, and the central hadron provides stability.
The possible crypto-heptaquark hadrons with exotic pentaquark flavours are
studied.Comment: 8 pages, 3 tables, talk presented at the International Workshop
PENTAQUARK04 July 20-23, 2004, SPring-8, Japa
Dynamically generated baryon resonances
Identifying a zero-range exchange of vector mesons as the driving force for
the s-wave scattering of pseudo-scalar mesons off the baryon ground states, a
rich spectrum of molecules is formed. We argue that chiral symmetry and
large- considerations determine that part of the interaction which
generates the spectrum. We suggest the existence of strongly bound
crypto-exotic baryons, which contain a charm-anti-charm pair. Such states are
narrow since they can decay only via OZI-violating processes. A narrow nucleon
resonance is found at mass 3.52 GeV. It is a coupled-channel bound state of the
system, which decays dominantly into the
channel. Furthermore two isospin singlet hyperon states at mass
3.23 GeV and 3.58 GeV are observed as a consequence of coupled-channel
interactions of the and states. Most striking is the small width of about 1
MeV of the lower state. The upper state may be significantly broader due to a
strong coupling to the state. The spectrum of crypto-exotic
charm-zero states is completed with an isospin triplet state at 3.93 GeV and an
isospin doublet state at 3.80 GeV. The dominant decay modes involve again the
meson.Comment: Talk presented at N*2005, 10 pages, 1 figur
Trends in crypto-currencies and blockchain technologies: A monetary theory and regulation perspective
The internet era has generated a requirement for low cost, anonymous and
rapidly verifiable transactions to be used for online barter, and fast settling
money have emerged as a consequence. For the most part, e-money has fulfilled
this role, but the last few years have seen two new types of money emerge.
Centralised virtual currencies, usually for the purpose of transacting in
social and gaming economies, and crypto-currencies, which aim to eliminate the
need for financial intermediaries by offering direct peer-to-peer online
payments.
We describe the historical context which led to the development of these
currencies and some modern and recent trends in their uptake, in terms of both
usage in the real economy and as investment products. As these currencies are
purely digital constructs, with no government or local authority backing, we
then discuss them in the context of monetary theory, in order to determine how
they may be have value under each. Finally, we provide an overview of the state
of regulatory readiness in terms of dealing with transactions in these
currencies in various regions of the world
Repeatable classical one-time-pad crypto-system with quantum mechanics
Classical one-time-pad key can only be used once. We show in this Letter that
with quantum mechanical information media classical one-time-pad key can be
repeatedly used. We propose a specific realization using single photons. The
reason why quantum mechanics can make the classical one-time-pad key repeatable
is that quantum states can not be cloned and eavesdropping can be detected by
the legitimate users. This represents a significant difference between
classical cryptography and quantum cryptography and provides a new tool in
designing quantum communication protocols and flexibility in practical
applications.
Note added: This work was submitted to PRL as LU9745 on 29 July 2004, and the
decision was returned on 11 November 2004, which advised us to resubmit to some
specialized journal, probably, PRA, after revision. We publish it here in
memory of Prof. Fu-Guo Deng (1975.11.12-2019.1.18), from Beijing Normal
University, who died on Jan 18, 2019 after two years heroic fight with
pancreatic cancer. In this work, we designed a protocol to repeatedly use a
classical one-time-pad key to transmit ciphertext using single photon states.
The essential idea was proposed in November 1982, by Charles H. Bennett, Gilles
Brassard, Seth Breidbart, which was rejected by Fifteenth Annual ACM Symposium
on Theory of Computing, and remained unpublished until 2014, when they
published the article, Quantum Cryptography II: How to re-use a one-time pad
safely even if P=NP, Natural Computing (2014) 13:453-458, DOI
10.1007/s11047-014-9453-6. We worked out this idea independently. This work has
not been published, and was in cooperated into quant-ph 706.3791 (Kai Wen, Fu
Guo Deng, Gui Lu Long, Secure Reusable Base-String in Quantum Key
Distribution), and quant-ph 0711.1642 (Kai Wen, Fu-Guo Deng, Gui Lu Long,
Reusable Vernam Cipher with Quantum Media).Comment: It was submitted to PRL in 2004. We designed a protocol to use
repeatedly a one-time-pad to transmit ciphertext using single photons. The
idea was proposed by Bennett, Brassard, Breidbart in 1982. Unknowing their
work, we rediscovered this idea independently. We publish it here in memory
of Prof. Fu-Guo Deng (1975.11.12-2019.1.18), who died after two years heroic
fight with pancreatic cance
Crypto-unitary forms of quantum evolution operators
For the description of quantum evolution, the use of a manifestly
time-dependent quantum Hamiltonian
is shown equivalent to the work with its simplified, time-independent
alternative . A tradeoff analysis is performed recommending
the latter option. The physical unitarity requirement is shown fulfilled in a
suitable ad hoc representation of Hilbert space.Comment: 15 p
Prefigurative Post-Politics as Strategy:The Case of Government-Led Blockchain Projects
Critically engaging with literature on post-politics, blockchain and algorithmic governance, and drawing also on knowledge gained from undertaking a three-year empirical study, the purpose of this article is to better understand the transformative capacity of government-led blockchain projects. Analysis of a diversity of empirical material, which was guided by a digital ethnography approach, is used to support the furthering of the existing debate on the nature of the post-political as a condition and/or strategy. Through these theoretical and empirical explorations, the article concludes that while the post-political represents a contingent political strategy by governmental actors, it could potentially impose an algorithmically enforced post-political ‘condition’ for the citizen. It is argued that the design, features and mechanisms of government-led projects are deliberately and strategically used to delimit a citizens’ political agency. In order to address this scenario, we argue that there is a need not only to analyse and contribute to the algorithmic design of blockchain projects (i.e. the affordances and constraints they set), but also to the metapolitical narrative underpinning them (i.e. the political imaginaries underlying the various government-led projects)
Community Structure in Industrial SAT Instances
Modern SAT solvers have experienced a remarkable progress on solving
industrial instances. Most of the techniques have been developed after an
intensive experimental process. It is believed that these techniques exploit
the underlying structure of industrial instances. However, there are few works
trying to exactly characterize the main features of this structure.
The research community on complex networks has developed techniques of
analysis and algorithms to study real-world graphs that can be used by the SAT
community. Recently, there have been some attempts to analyze the structure of
industrial SAT instances in terms of complex networks, with the aim of
explaining the success of SAT solving techniques, and possibly improving them.
In this paper, inspired by the results on complex networks, we study the
community structure, or modularity, of industrial SAT instances. In a graph
with clear community structure, or high modularity, we can find a partition of
its nodes into communities such that most edges connect variables of the same
community. In our analysis, we represent SAT instances as graphs, and we show
that most application benchmarks are characterized by a high modularity. On the
contrary, random SAT instances are closer to the classical Erd\"os-R\'enyi
random graph model, where no structure can be observed. We also analyze how
this structure evolves by the effects of the execution of a CDCL SAT solver. In
particular, we use the community structure to detect that new clauses learned
by the solver during the search contribute to destroy the original structure of
the formula. This is, learned clauses tend to contain variables of distinct
communities
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