The Excited Baryon Analysis Center (EBAC), which is associated with the
Theory Group at Jefferson Laboratory, was initiated in 2006. Its main goal is
to extract and interpret properties of nucleon resonances (N*) from the world
data of meson production reactions induced by pions, photons and electrons. We
review the main accomplishments of the center since then and sketch its near
future perspectives.Comment: Invited plenary talk, to appear in the Proceedings of XIII
International Conference on Hadron Spectroscopy, November 29 - December 4,
2009, Florida State University. (v2, references added, fig6 slightly
modified
The use of relativistic quark models with simple parametric wave functions
for the understanding of the electromagnetic structure of nucleons together
with their electromagnetic transition to resonances is discussed. The
implications of relativity in the different ways it can be implemented in a
simple model are studied together with the role played by mixed symmetry
s-state and D-state deformations of the rest frame wave functions of the
nucleon and Delta resonance.Comment: To appear in the proceedings of "Shape of Hadrons" workshop, Athens,
Greece, 27-29 Apr 200
In this work we present and formally analyze CHAT-SRP (CHAos based
Tickets-Secure Registration Protocol), a protocol to provide interactive and
collaborative platforms with a cryptographically robust solution to classical
security issues. Namely, we focus on the secrecy and authenticity properties
while keeping a high usability. In this sense, users are forced to blindly
trust the system administrators and developers. Moreover, as far as we know,
the use of formal methodologies for the verification of security properties of
communication protocols isn't yet a common practice. We propose here a
methodology to fill this gap, i.e., to analyse both the security of the
proposed protocol and the pertinence of the underlying premises. In this
concern, we propose the definition and formal evaluation of a protocol for the
distribution of digital identities. Once distributed, these identities can be
used to verify integrity and source of information. We base our security
analysis on tools for automatic verification of security protocols widely
accepted by the scientific community, and on the principles they are based
upon. In addition, it is assumed perfect cryptographic primitives in order to
focus the analysis on the exchange of protocol messages. The main property of
our protocol is the incorporation of tickets, created using digests of chaos
based nonces (numbers used only once) and users' personal data. Combined with a
multichannel authentication scheme with some previous knowledge, these tickets
provide security during the whole protocol by univocally linking each
registering user with a single request. [..]Comment: 32 pages, 7 figures, 8 listings, 1 tabl
The Laura and John Arnold Foundation (LJAF) released "A Pivotal Moment: Assessing Houston's Plan for Pension Reform," a report that provides an in-depth analysis of the City of Houston's pension reform proposal currently pending in the Texas Legislature. The report finds that the proposal includes important changes that would help protect workers and taxpayers. The reform plan was developed following discussions between Mayor Sylvester Turner and the Houston Police Officers' Pension System, the Houston Municipal Employees Pension System, and the Houston Firefighters' Relief and Retirement Fund.LJAF Vice President Josh McGee and LJAF Sustainable Public Finance Analyst Paulina S. Diaz Aguirre co-authored the report after analyzing the city's proposal and conducting independent pension modeling. They say that it is incumbent on local leaders and state legislators to work together. "There are just a few weeks left in the 2017 session—and without the ability to make changes to the pension systems on its own—the city is running out of time," the report states. "Without changes, the debt could spiral into a full-scale financial crisis. The city cannot allow that to happen. Its financial future hangs in the balance and will be decided in large part in the next month."Houston currently owes 8.2billioninpensiondebt—morethananyothercityinTexas.Itdoesnothaveenoughmoneytopayfornearlyhalfoftheretirementbenefitsworkershavealreadyearned.Thisunfundedliabilitythreatensworkers′retirementsecurityandhasadirectimpactoncityfinances.Duringthepast10years,thecityhascutpublicsafetypositionsevenasspendingonpublicsafetyhasgrownbyhundredsofmillionsofdollarsduetoa55percentincreaseinpensioncosts.Theproposalseekstoaddresscriticalflawsinthecity′sfundingpractices.Undertheproposal,thecitywouldloweritsassumedrateofreturnoninvestmentsforallplansfrom8percentormoreto7percent;reducebenefitsforpublicworkers;andimplementafinancialcorridorprovisionthatwouldcapthecity′scontributionstothepensionplans.Thefinancialcorridorprovisionisakeyelementoftheproposal.Theprovisionwouldsetaminimumandmaximumcitycontributionrateforeachplan.Ifthecityweretohitorsurpassthemaximum,workerswouldberequiredtomakeadditionalbenefitconcessionstobringcostsbackunderthecap.LJAF′sanalysisshowsthatthismechanismwouldprovidesubstantialnewprotectionsfortaxpayersbutwouldalsosignificantlyincreaseworkers′exposuretorisk.Thereportstatesthattheproposal′slong−termimpactonworkerswoulddependondemographictrendsandtheplans′investmentperformance,twofactorsthatwouldinfluencehowoftenthecitywouldhitthecap.Forexample,LJAF′smodelingshowsthatthereisatwoinfive(40percent)chancethatthecity′scontributionratewouldhitthemaximumforthepolicefundatleastonceby2027.Ifthepoliceplanweretoearnlessthan7percentonitsinvestmentsintheshortorlongterm,contributionrateswouldhitthecapevensooner.Ifinvestmentreturnsmatchthecity′sassumptions,thereisroughlyaoneinthree(33percent)chancethatcontributionratesformembersofthepoliceplanwouldincreasebyfivepercentagepointsormoreinthenextdecade.Giventhatmembersofthepoliceplan—aswellasmembersoftheotherplans—havealreadyagreedtobillionsofdollarsinconcessions,McGeeandDiazAguirreexplainthatthecityhasanobligationtoupholditsendofthebargain.Theystatethatthecityshouldmakepaymentsontimeandinfullandshouldtakesteps—suchaslimitinginvestmentsinriskyassetsincludingrealestate,privateequity,andhedgefunds—toprotectworkers.Inaddition,iftheproposalisimplemented,thereportstatesthatthecityshouldalsomakegoodonitspromisetoprovidealump−sumpaymenttothetwoplanswiththelargestdeficits—thepoliceandmunicipalemployeesplans.Thecityhasproposedissuing1 billion in pension obligation bonds to cover the payments. To benefit financially, Houston would need to earn more in the market than it costs to borrow the money. Given the current market conditions, the spread between expected bond interest rates and expected returns is relatively small. Despite the fact that the bonds pose some risk, the report argues that they are a good-faith measure that reflects the city's commitment to upholding funding promises.The report concludes that, "In the short term, the proposal would place the pension plans—and the city—on firmer financial footing. The long-term impact would depend on how the changes are implemented." It also states that Houston should make further changes to establish a comprehensive, permanent solution to its pension problems. This would include creating retirement systems for new workers that are simpler and easier to manage such as a Defined Contribution plan or a Cash Balance plan
In this paper, we formalize the notion of lambda-AT-model (where λ is
a non-null integer) for a given chain complex, which allows the computation of
homological information in the integer domain avoiding using the Smith Normal
Form of the boundary matrices. We present an algorithm for computing such a
model, obtaining Betti numbers, the prime numbers p involved in the invariant
factors of the torsion subgroup of homology, the amount of invariant factors
that are a power of p and a set of representative cycles of generators of
homology mod p, for each p. Moreover, we establish the minimum valid lambda for
such a construction, what cuts down the computational costs related to the
torsion subgroup. The tools described here are useful to determine topological
information of nD structured objects such as simplicial, cubical or simploidal
complexes and are applicable to extract such an information from digital
pictures.Comment: Journal Image and Vision Computing, Volume 27 Issue 7, June, 200