435 research outputs found
Quantum field-theoretic machine learning
No full textWe derive machine learning algorithms from discretized Euclidean field theories, making inference and learning possible within dynamics described by quantum field theory. Specifically, we demonstrate that the ϕ4 scalar field theory satisfies the Hammersley-Clifford theorem, therefore recasting it as a machine learning algorithm within the mathematically rigorous framework of Markov random fields. We illustrate the concepts by minimizing an asymmetric distance between the probability distribution of the ϕ4 theory and that of target distributions, by quantifying the overlap of statistical ensembles between probability distributions and through reweighting to complex-valued actions with longer-range interactions. Neural network architectures are additionally derived from the ϕ4 theory which can be viewed as generalizations of conventional neural networks and applications are presented. We conclude by discussing how the proposal opens up a new research avenue, that of developing a mathematical and computational framework of machine learning within quantum field theory
Inverse Renormalization Group in Quantum Field Theory
No full textWe propose inverse renormalization group transformations within the context of quantum field theory that produce the appropriate critical fixed point structure, give rise to inverse flows in parameter space, and evade the critical slowing down effect in calculations pertinent to criticality. Given configurations of the two-dimensional φ4 scalar field theory on sizes as small as V=82, we apply the inverse transformations to produce rescaled systems of size up to V′=5122 which we utilize to extract two critical exponents. We conclude by discussing how the approach is generally applicable to any method that successfully produces configurations from a statistical ensemble and how it can give novel insights into the structure of the renormalization group
I rilievi per la mostra e il libro su Biagio Rossetti
No full textNel 1960 Bruno Zevi diede alle stampe il volume Biagio Rossetti architetto ferrarese. Il primo urbanista moderno europeo. Nell’opera, che conta 727 pagine, sono presenti 200 disegni di rilievo riferibili ad una parte delle architetture indagate: si tratta di 19 edifici, di cui 12 civili e 7 sacri.
In chiusura al volume Zevi sintetizza gli eventi che resero possibile la realizzazione prima della famosa mostra Identità di Biagio Rossetti, inaugurata il 28 giugno 1956 nel Ridotto del Teatro Comunale e, quattro anni dopo, dell’imponente libro, indicando i nomi di coloro che collaborarono all’iniziativa. L’autore cita la prof. Luisa Balboni sindaco di Ferrara, e l’assessore alle BB. AA. Mario Roffi che nel 1955 si rivolsero all’allora preside dell’Istituto Universitario di Architettura di Venezia, Giuseppe Samonà per celebrare il 440° anniversario della morte di Rossetti. Zevi afferma che «[...] gli studenti ed io accettammo con entusiasmo di ordinare una mostra: dedicai il mio corso al maestro ferrarese, mentre gli allievi del primo anno rilevarono vari monumenti, e quelli del secondo, con la guida del mio assistente dott. Giuseppe Mazzariol, svolsero indagini documentate in una serie di tesine.» Questo scritto propone alcune riflessioni sul ruolo del rilievo nella vicenda editoriale zeviana e nei suoi esiti.In 1960, Bruno Zevi published the book Biagio Rossetti architetto ferrarese. Il primo urbanista moderno europeo. In the 727 page long work, there are 200 survey drawings, some of which refer to the investigated architectures: these are 19 buildings (twelve non-religious and seven religious).
At the end of the publication, Zevi summarizes the events that made the realization of the book possible before the famous exhibition Identità di Biagio Rossetti, inaugurated on June 28 1956 in the Ridotto of the Municipal Theater. Four years later, the imposing book indicated the names of those who collaborated in the initiative. The author quotes prof. Luisa Balboni, mayor of Ferrara, and the assessore BB. AA. Mario Roffi, who in 1955 contacted the then dean of the University Institute of Architecture in Venice, Giuseppe Samonà to celebrate the 440th anniversary of Rossetti's death. Zevi says "[...] the students and I enthusiastically accepted to organize an exhibition: I dedicated my course to the celebrated Ferrara architect, the first-year students surveyed various monuments, while those of the second year carried out documented investigations in a series of papers with the guidance of my assistant Dr Giuseppe Mazzariol."
This paper offers some reflections on the survey's role in Zevy’s work and its outcomes
Infrared regime of SU(2) with one adjoint Dirac flavor
No full textSU(2) gauge theory with one Dirac flavor in the adjoint representation is investigated on a lattice. Initial results for the gluonic and mesonic spectrum, static potential from Wilson and Polyakov loops, and the anomalous dimension of the fermionic condensate from the Dirac mode number are presented. The results found are not consistent with conventional confining behavior, pointing instead tentatively towards a theory lying within or very near the onset of the conformal window, with the anomalous dimension of the fermionic condensate in the range 0.9≲γ∗≲0.95. The implications of our work for building a viable theory of strongly interacting dynamics beyond the standard model are discussed
Simulations of QCD and QED with C* boundary conditions
No full textWe present exploratory results from dynamical simulations of QCD in isolation, as well as QCD coupled to QED, with C* boundary conditions. In finite volume, the use of C* boundary conditions allows for a gauge invariant and local formulation of QED without zero modes. In particular we show that the simulations reproduce known results and that masses of charged mesons can be extracted in a completely gauge invariant way. For the simulations we use a modified version of the HiRep code. The primary features of the simulation code are presented and we discuss some details regarding the implementation of C* boundary conditions and the simulated lattice action.Preprint: CP3-Origins-2017-046 DNRF90, CERN-TH-2017-214We present exploratory results from dynamical simulations of QCD in isolation, as well as QCD coupled to QED, with C* boundary conditions. In finite volume, the use of C* boundary conditions allows for a gauge invariant and local formulation of QED without zero modes. In particular we show that the simulations reproduce known results and that masses of charged mesons can be extracted in a completely gauge invariant way. For the simulations we use a modified version of the HiRep code. The primary features of the simulation code are presented and we discuss some details regarding the implementation of C* boundary conditions and the simulated lattice action
Money, politics and a future for the international financial system
No full textIn developing the architecture for a financial system, the challenge is to combine deregulation and safety nets against systemic failure with effective prudential regulation and oversight. The author analyzes three approaches to choosing an adequate regulatory framework for a financial system. a) Those most worried about panic and herd behavior tend to favor relatively extensive controls on financial institutions'activities, including controls on interest rates and on the volume and direction of lending. b) Those most concerned about moral hazard advocate abolishing controls and safety nets, seeing the solution is stronger market discipline and reduced powers and discretion for regulators. c) Mainstream opinion advocates a mix of measures, to both strengthen market discipline and improve regulatory oversight. The approach a county opts for depends on 1) which monetary and exchange rate regime it chooses, 2) whether it is more concerned about moral hazard or about panic and herd behavior, and 3) how the politics of reform shape its solutions. The author suggests a scenario for development of the global financial system over the next two or three decades that assumes that the final outcome will resemble the market solution - not because that is the optimal policy choice but because of how political weakness will interact with advances in settlement technology. In the author's scenario, the world moves toward a monetary system in which fixed exchange rate systems or de facto currency competition limit the power of central banks. This limits options for discretionary and open-ended liquidity support to help deal with systemic financial crises. The costs of inflexible exchange rates are moderated by new types of wage contracts, using units of account that are correlated with the shocks a particular industry or kind of contract faces -- thus maintaining the positive aspects of monetary systems with flexible nominal exchange rates. Mistrust in monetary authorities and the emergence of private settlements lead to a return of asset-backed money as the means of payment. The disciplines on financial systems come to resemble somewhat those of historical"free banking"systems, with financial institutions requiring high levels of equity and payments systems protected only by limited, fully funded safety nets.Banks&Banking Reform,Fiscal&Monetary Policy,Financial Intermediation,Payment Systems&Infrastructure,Economic Theory&Research,Banks&Banking Reform,Economic Theory&Research,Macroeconomic Management,Financial Intermediation,Financial Economics
Non-perturbative results for large-N gauge theories
No full textIt has been known for a long time that large- methods can give invaluable insights into non-perturbative phenomena such as confinement. Lattice techniques can be used to compute quantities at large . In this contribution, I review some recent large-N lattice results and discuss their implications for our understanding of non-perturbative QCD
Chiral transition and deconfinement in N_f = 2 QCD
No full textThe transition is studied by means of a disorder parameter detecting
condensation of magnetic monopoles in the vacuum. The deconfining transition is
found to coincide with the chiral transition and the susceptibility \rho,
related to the disorder parameter, is consistent with a first order phase
transition
Topological Data Analysis of Monopoles in U(1) Lattice Gauge Theory — Data Release
No full text<div>This release contains data used to prepare the publication <a href="https://arxiv.org/abs/2403.07739">X. Crean, J. Giansiracusa and B. Lucini, Topological Data Analysis of Monopoles in U(1) Lattice Gauge Theory (2024)</a>. There exists an <a href="https://doi.org/10.5281/zenodo.10806185">accompanying software release</a> that explains in detail how to extract and use the compressed data files on a Linux distribution (or compatible environment).</div><p>XC was supported by the Additional Funding Programme for Mathematical Sciences, delivered by EPSRC (EP/V521917/1) and the Heilbronn Institute for Mathematical Research. JG was supported by EPSRC grant EP/R018472/1 through the Oxford-Liverpool-Durham Centre for Topological Data Analysis. The work of BL was partly supported by the EPSRC ExCALIBUR ExaTEPP project EP/X017168/1 and by the STFC Consolidated Grants No. ST/T000813/1 and ST/X000648/1. Numerical simulations have been performed on the Swansea SUNBIRD cluster, part of the Supercomputing Wales project. Supercomputing Wales is part funded by the European Regional Development Fund (ERDF) via Welsh Government.</p>
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