Isentropic Curves at Magnetic Phase Transitions

Experiments on cold atom systems in which a lattice potential is ramped up on a confined cloud have raised intriguing questions about how the temperature varies along isentropic curves, and how these curves intersect features in the phase diagram. In this paper, we study the isentropic curves of two models of magnetic phase transitions- the classical Blume-Capel Model (BCM) and the Fermi Hubbard Model (FHM). Both Mean Field Theory (MFT) and Monte Carlo (MC) methods are used. The isentropic curves of the BCM generally run parallel to the phase boundary in the Ising regime of low vacancy density, but intersect the phase boundary when the magnetic transition is mainly driven by a proliferation of vacancies. Adiabatic heating occurs in moving away from the phase boundary. The isentropes of the half-filled FHM have a relatively simple structure, running parallel to the temperature axis in the paramagnetic phase, and then curving upwards as the antiferromagnetic transition occurs. However, in the doped case, where two magnetic phase boundaries are crossed, the isentrope topology is considerably more complex

Determining the Cost of Business Continuity Management - A Case Study of IT Service Continuity Management Activity Cost Analysis

This single organisation case study discusses the cost of business continuity management in IT services. Information technology (IT) expenses can amount to a substantial part of operational costs in a company, and IT leaders tend to aim for thorough IT cost management to meet financial targets. Thus, information security activities such as business continuity management (BCM) rank among the most important concerns for IT leaders. Despite the concerns of IT management, senior management appears to be hesitant to spend on BCM as much as IT management would hope for. Senior management may struggle with the question of how to justify spending on an activity that proves its usefulness only when a rare event occurs. The challenge for measuring costs of sociotechnical activities was the inspiration for this work – to find out whether the cost of business continuity management (BCM) could be explained better to help decision making. Two main paradigms emerged from literature – BCM activities in the context of organisational routines, and IT cost and information security cost classifications. The theoretical assumption was that the relationship between IT costs and BCM activities emulates the activity- based costing theory (ABC) – the premise of cause-and-effect relationship between activities and costs. The key question is “How to determine the cost of BCM activities in IT services?” To find out, I used comprehensive archival data set from a case company and designed a retrospective quantitative model to analyse the association between BCM activities and IT costs. By employing causal-comparative method and multiple linear regression analysis, I compared distinct groups of IT services to determine how much of the variation in IT costs could be explained by BCM activities. In addition, I measured the relative effect of each independent variable towards the total cost of BCM. As both statistical and practical significance test results were supported, several interesting results were observed between BCM activities and IT costs – namely human, technology and organisational resources, as well as IT service designs. The research presents two theoretical contributions and one empirical contribution to the theory. The first and primary contribution is the BCM activity cost model. This is the final product for the main research question of determining the cost of BCM in IT services. The second contribution is the total cost of BCM framework. This framework contributes to the broader academic discussion of information system (IS) cost taxonomies in IT services and information security. The third contribution is empirical confirmation how to observe unknown cost effects by multiple regression analysis. Learnings from this research can contribute IS researchers focused on the economic aspects of IS and IT. The research also introduces three practical contributions. The first one considers the observation of overall BCM cost effects on IT services. Although the results of a single case study cannot be generalized directly to every organization, information herein may aid companies to evaluate BCM impact on their budgets. The second practical contribution considers the challenges regarding measurement of activity costs that can be difficult to observe directly. Within the limitations of this research, nothing here suggests that the BCM activity cost model could not be productized and integrated into other cost appraisal tools in a company or applied in other IT service management areas. The last important practical contribution are the definitions of BCM activity cost variables. Confirming the cost association between theoretical and empirical BCM frameworks can help BCM professionals to promote BCM process.Tämä yhden organisaation tapaustutkimus pohtii jatkuvuudenhallinnan kustannusten osuutta tietojärjestelmäpalveluissa. Informaatioteknologian (IT) kustannukset saattavat muodostaa merkittävän osa yrityksen menoista, ja IT-johtajat pyrkivät yleensä tarkkaan kulujenhallintaan saavuttaakseen yrityksen taloudelliset tavoitteet. Siksi tietoturva-aktiiviteetit kuten jatkuvuudenhallinta (business continuity management, BCM) ovat heidän olennaisimpia huolenaiheitaan. IT-johtajien huolista huolimatta ylin johto ei yleensä ole kovin innokas panostamaan BCM:ään niin paljon kuin IT-johto toivoisi. Ylin johto saattaa tuskailla sen kanssa, miten perustella kulut toimiin, joita kaivataan vain harvinaisissa poikkeustilanteissa. Sosioteknisten kulujen mittaamisen haaste antoi inspiraation tälle tutkimukselle; tavoite oli selvittää, olisiko mahdollista selittää BCM-kustannuksia paremmin päätöksenteon tueksi. Kirjallisuudesta nousee esiin kaksi keskeistä aihepiiriä: BCM organisaation toimintatapojen kontekstissa sekä IT-ja tietoturvakulujen luokittelu. Teoreettinen oletus oli, että IT-kulujen ja BCM- toimenpiteiden suhde emuloi toimintolaskennan (activity-based costing, ABC) teoriaa – se, että toimenpiteiden ja kulujen välillä on syy-seuraussuhde. Avainkysymys on ”Miten määritellä BCM- toimenpiteiden kulut IT-palveluissa?” Tämän selvittämiseksi käytin kattavaa arkistodataa caseyhtiöstä ja kehitin retrospektiivisen kvantitatiivisen mallin analysoidakseni BCM-toimenpiteiden ja IT-kulujen suhdetta. Kausaalis-komparatiivisen metodin ja lineaarisen regressioanalyysin avulla vertailin erilaisia IT-palvelujen ryhmiä selvittääkseni missä määrin BCM-toimenpiteet voisivat selittää IT-kulujen vaihtelua. Lisäksi mittasin jokaisen muuttujan suhteellisen vaikutuksen BCM:n kokonaiskustannuksiin. Kun sekä tilastolliset että käytännölliset testitulokset huomioitiin, BCM- toimenpiteiden ja IT-kulujen suhteesta ilmeni useita kiinnostavia tuloksia: sekä inhimillisiä että teknologia- ja organisaatioresursseihin ja IT-palvelujen muotoiluun liittyviä. Tutkimus tuotti kaksi teoreettista kontribuutiota sekä yhden empiirisen todistuksen teorialle. Ensimmäinen ja olennaisin näistä on BCM-toimenpiteiden kustannusmalli. Tämä lopputuotos vastaa tutkielman avainkysymykseen BCM-kuluista IT-palveluissa. Toinen kontribuutio on BCM-kehyksen kokonaishinta. Tämä voi ruokkia laajempaa akateemista keskustelua tietojärjestelmien (information system, IS) kustannustaksonomioista IT- palveluissa ja tietoturvassa. Kolmas kontribuutio, empiirinen todistus, osoittaa epäsuorien kulujen mittaamisen olevan mahdollista regressioanalyysiä hyödyntäen. Tutkimuksen havainnoista voi olla hyötyä IS:n ja IT:n taloudellisiin aspekteihin keskittyneille IS-tutkijoille. Tutkimuksesta nousee esiin myös kolme käytännön kontribuutiota. Ensimmäinen liittyy siihen, miten BCM-kokonaiskulujen vaikutuksia IT-palveluihin seurataan. Vaikka yhden tapaustutkimuksen tuloksia ei voida yleistää, tutkimuksen havainnot voivat auttaa yrityksiä arvioimaan BCM:n vaikutuksia budjetteihinsa. Toinen käytännön kontribuutio liittyy haasteisiin siinä, kuinka mitata toimenpidekustannuksia, joita on hankala tarkkailla suoraan. Tämän tutkimuksen rajoissa ei ilmennyt mitään syytä sille, etteikö BCM-toimenpiteiden kustannusmallia voitaisi tuotteistaa ja integroida yrityksen muihin kustannusarviotyökaluihin tai etteikö sitä voisi soveltaa muille IT-palvelujen hallinnon alueille. Viimeinen merkittävä käytännön kontribuutio on BCM-toimenpiteiden kustannusmuuttujien määrittely. BCM-ammattilaiset voivat helpommin edistää BCM-prosessia, kun teoreettisten ja empiiristen BCM-kehysten kulujen vastaavuus vahvistetaan

Effect of Correlated Lateral Geniculate Nucleus Firing Rates on Predictions for Monocular Eye Closure Versus Monocular Retinal Inactivation

Monocular deprivation experiments can be used to distinguish between different ideas concerning properties of cortical synaptic plasticity. Monocular deprivation by lid suture causes a rapid disconnection of the deprived eye connected to cortical neurons whereas total inactivation of the deprived eye produces much less of an ocular dominance shift. In order to understand these results one needs to know how lid suture and retinal inactivation affect neurons in the lateral geniculate nucleus (LGN) that provide the cortical input. Recent experimental results by Linden et al. showed that monocular lid suture and monocular inactivation do not change the mean firing rates of LGN neurons but that lid suture reduces correlations between adjacent neurons whereas monocular inactivation leads to correlated firing. These, somewhat surprising, results contradict assumptions that have been made to explain the outcomes of different monocular deprivation protocols. Based on these experimental results we modify our assumptions about inputs to cortex during different deprivation protocols and show their implications when combined with different cortical plasticity rules. Using theoretical analysis, random matrix theory and simulations we show that high levels of correlations reduce the ocular dominance shift in learning rules that depend on homosynaptic depression (i.e., Bienenstock-Cooper-Munro type rules), consistent with experimental results, but have the opposite effect in rules that depend on heterosynaptic depression (i.e., Hebbian/principal component analysis type rules)

When organisational effectiveness fails: business continuity management and the paradox of performance

Purpose: The aim of the paper is to consider the nature of the business continuity management (BCM) process and to frame it within wider literature on the performance of socio-technical systems. Despite the growth in BCM activities in organisations, some questions remain as to whether academic research has helped to drive this process. The paper seeks to stimulate discussion within this journal of the interplay between organisational performance and BCM and to frame it within the context of the potential tensions between effectiveness and efficiency. Design/methodology/approach: The paper considers how BCM is defined within the professional and academic communities that work in the area. It deconstructs these definitions in order to and set out the key elements of BCM that emerge from the definitions and considers how the various elements of BCM can interact with each other in the context of organisational performance. Findings: The relationships between academic research in the area of crisis management and the practice-based approaches to business continuity remain somewhat disjointed. In addition, recent work in the safety management literature on the relationships between success and failure can be seen to offer some interesting challenges for the practice of business continuity. Practical implications: The paper draws on some of the practice-based definitions of BCM and highlights the limitations and challenges associated with the construct. The paper sets out challenges for BCM based upon theoretical challenges arising in cognate areas of research. The aim is to ensure that BCM is integrated with emerging concepts in other aspects of the management of uncertainty and to do so in a strategic context. Originality/value: Academic research on performance reflects both the variety and the multi-disciplinary nature of the issues around measuring and managing performance. Failures in organisational performance have also invariably attracted considerable attention due to the nature of a range of disruptive events. The paper reveals some of the inherent paradoxes that sit at the core of the BCM process and its relationships with organisational performance

Bost-Connes-Marcolli systems for Shimura varieties. I. Definitions and formal analytic properties

We construct a quantum statistical mechanical system $(A,s)$ analogous to the systems constructed by Bost-Connes and Connes-Marcolli in the case of Shimura varieties. Along the way, we define a new Bost-Connes system for number fields which has the ``correct'' partition function and the ``correct'' symmetries. We give a formalism that applies to general Shimura data $(G,X)$. The object of this series of papers is to show that these systems exhibit phase transitions with spontaneous symmetry breaking, and to classify their KMS states, at least for low temperature.Comment: 37 pages, LaTe

OFAR-CM: Efficient Dragonfly networks with simple congestion management

Dragonfly networks are appealing topologies for large-scale Data center and HPC networks, that provide high throughput with low diameter and moderate cost. However, they are prone to congestion under certain frequent traffic patterns that saturate specific network links. Adaptive non-minimal routing can be used to avoid such congestion. That kind of routing employs longer paths to circumvent local or global congested links. However, if a distance-based deadlock avoidance mechanism is employed, more Virtual Channels (VCs) are required, what increases design complexity and cost. OFAR (On-the-Fly Adaptive Routing) is a previously proposed routing that decouples VCs from deadlock avoidance, making local and global misrouting affordable. However, the severity of congestion with OFAR is higher, as it relies on an escape sub network with low bisection bandwidth. Additionally, OFAR allows for unlimited misroutings on the escape sub network, leading to unbounded paths in the network and long latencies. In this paper we propose and evaluate OFAR-CM, a variant of OFAR combined with a simple congestion management (CM) mechanism which only relies on local information, specifically the credit count of the output ports in the local router. With simple escape sub networks such as a Hamiltonian ring or a tree, OFAR outperforms former proposals with distance-based deadlock avoidance. Additionally, although long paths are allowed in theory, in practice packets arrive at their destination in a small number of hops. Altogether, OFAR-CM constitutes the first practicable mechanism to the date that supports both local and global misrouting in Dragonfly networks.The research leading to these results has received funding from the European Research Council under the European Union’s Seventh Framework Programme (FP/2007-2013) / ERC Grant Agreement n. ERC-2012-Adg-321253- RoMoL, the Spanish Ministry of Science under contracts TIN2010-21291-C02-02, TIN2012-34557, and by the European HiPEAC Network of Excellence. M. García participated in this work while affiliated with the University of Cantabria.Peer ReviewedPostprint (author's final draft

Comparison between Oja's and BCM neural networks models in finding useful projections in high-dimensional spaces

This thesis presents the concept of a neural network starting from its corresponding biological model, paying particular attention to the learning algorithms proposed by Oja and Bienenstock Cooper & Munro. A brief introduction to Data Analysis is then performed, with particular reference to the Principal Components Analysis and Singular Value Decomposition. The two previously introduced algorithms are then dealt with more thoroughly, going to study in particular their connections with data analysis. Finally, it is proposed to use the Singular Value Decomposition as a method for obtaining stationary points in the BCM algorithm, in the case of linearly dependent inputs

Level Truncation and Rolling the Tachyon in the Lightcone Basis for Open String Field Theory

A recent paper by Gross and Erler (hep-th/0406199) showed that by making a certain well-defined, unitary transformation on the mode basis for the open bosonic string--one that identifies the lightcone component of position with the string midpoint--it is possible to render the action for cubic string field theory local in lightcone time. In this basis, then, cubic string field theory possesses a well-defined initial value formulation and a conserved Hamiltonian. With this new understanding it seems natural to study time dependent solutions representing the the decay of an unstable D-branes. In this paper we study such solutions using level truncation of mode oscillators in the lightcone basis, finding both homogenous solutions by perturbatively expanding the string field in modes $e^{nt}$, and inhomogenous solutions by integrating the equations of motion on a lattice. Truncating the theory to level $(\tilde{2},\tilde{4})$ in $\alpha^+$ oscillators, we find time dependent solutions whose behavior seems to converge to that of earlier solutions constructed in the center of mass basis, where the cubic action contains an infinite number of time derivatives. We further construct time-dependent inhomogeneous solutions including all fields up to level $(\tilde{2},\tilde{4})$. These solutions at the outset display rather erratic behavior due to an unphysical instability introduced by truncating the theory at the linear level. However upon truncating away the field responsible for the instability, we find more reasonable solutions which may possibly represent an approximation to tachyon matter. We conclude with some discussion of future directions.Comment: 29 pages, 21 figure