Advanced Modeling of Cold-Formed Steel Walls under Fire

This paper discusses an advanced finite element model able to simulate the structural response of cold-formed steel walls during standard fire tests. The model includes experimental thermo-mechanical properties of materials, geometric imperfections, and temperature distributions on studs and sheathing boards. The model is capable of reasonably predicting the thermal bowing of walls, and estimating the shape, size and amount of joint openings between gypsum boards over time of fire exposure. Numerical results validated with experimental data indicate that the maximum out-of-plane displacements due to thermal gradients occur near the wall mid-height. Early in the heating process, joint openings develop on the exposed side of walls due to thermal bowing and contraction of gypsum boards at elevated temperatures, potentially altering the heat transfer and affecting the fire resistance of the entire system. Future work aims to utilize high fidelity modeling to study the response of load bearing cold-formed steel systems subjected to fire, and optimize their fire resistance

Black holes admitting a Freudenthal dual

The quantised charges x of four dimensional stringy black holes may be assigned to elements of an integral Freudenthal triple system whose automorphism group is the corresponding U-duality and whose U-invariant quartic norm Delta(x) determines the lowest order entropy. Here we introduce a Freudenthal duality x -> \tilde{x}, for which \tilde{\tilde{x}}=-x. Although distinct from U-duality it nevertheless leaves Delta(x) invariant. However, the requirement that \tilde{x} be integer restricts us to the subset of black holes for which Delta(x) is necessarily a perfect square. The issue of higher-order corrections remains open as some, but not all, of the discrete U-duality invariants are Freudenthal invariant. Similarly, the quantised charges A of five dimensional black holes and strings may be assigned to elements of an integral Jordan algebra, whose cubic norm N(A) determines the lowest order entropy. We introduce an analogous Jordan dual A*, with N(A) necessarily a perfect cube, for which A**=A and which leaves N(A) invariant. The two dualities are related by a 4D/5D lift.Comment: 32 pages revtex, 10 tables; minor corrections, references adde

Cold Nuclear Matter In Holographic QCD

We study the Sakai-Sugimoto model of holographic QCD at zero temperature and finite chemical potential. We find that as the baryon chemical potential is increased above a critical value, there is a phase transition to a nuclear matter phase characterized by a condensate of instantons on the probe D-branes in the string theory dual. As a result of electrostatic interactions between the instantons, this condensate expands towards the UV when the chemical potential is increased, giving a holographic version of the expansion of the Fermi surface. We argue based on properties of instantons that the nuclear matter phase is necessarily inhomogeneous to arbitrarily high density. This suggests an explanation of the "chiral density wave" instability of the quark Fermi surface in large N_c QCD at asymptotically large chemical potential. We study properties of the nuclear matter phase as a function of chemical potential beyond the transition and argue in particular that the model can be used to make a semi-quantitative prediction of the binding energy per nucleon for nuclear matter in ordinary QCD.Comment: 31 pages, LaTeX, 1 figure, v2: some formulae corrected, qualitative results unchange

A diagrammatic derivation of the meson effective masses in the neutral color-flavor-locked phase of Quantum Chromodynamics

We offer a diagrammatic derivation of the effective masses of the axial flavor excitations in the electrical and color neutral CFL phase of QCD. In particular we concentrate on the excitations with the quantum numbers of the kaons: we show how their effective chemical potentials, responsible of their Bose-Einstein condensation and found previously on the basis of pure symmetry arguments, arise at the microscopic level by loop effects. We perform also the numerical evaluation of the relevant loops in the whole CFL regime $M_s^2/2\mu\Delta\leqslant 1$, showing the existence of the enhancement of the kaon condensation with respect to the lowest order result. Finally we discuss the role of electrical and color neutrality in the microscopic calculation.Comment: 10 pages, 2 figures, RevTeX4 style. Version accepted for publication on JHEP. Some minor change in the tex

Nonassociative differential extensions of characteristic p

Let F be a field of characteristic p. We define and investigate nonassociative differential extensions of F and of a finite-dimensional central division algebra over F and give a criterium for these algebras to be division. As special cases, we obtain classical results for associative algebras by Amitsur and Jacobson. We construct families of nonassociative division algebras which can be viewed as generalizations of associative cyclic extensions of a purely inseparable field extension of exponent one or a central division algebra. Division algebras which are nonassociative cyclic extensions of a purely inseparable field extension of exponent one are particularly easy to obtain

Quark Coulomb Interactions and the Mass Difference of Mirror Nuclei

We study the Okamoto-Nolen-Schiffer (ONS) anomaly in the binding energy of mirror nuclei at high density by adding a single neutron or proton to a quark gluon plasma. In this high-density limit we find an anomaly equal to two-thirds of the Coulomb exchange energy of a proton. This effect is dominated by quark electromagnetic interactions---rather than by the up-down quark mass difference. At normal density we calculate the Coulomb energy of neutron matter using a string-flip quark model. We find a nonzero Coulomb energy because of the neutron's charged constituents. This effect could make a significant contribution to the ONS anomaly.Comment: 4 pages, 2 figs. sub. to Phys. Rev. Let

Higher Loop Bethe Ansatz for Open Spin-Chains in AdS/CFT

We propose a perturbative asymptotic Bethe ansatz (PABA) for open spin-chain systems whose Hamiltonians are given by matrices of anomalous dimension for composite operators, and apply it to two types of composite operators related to two different brane configurations. One is an AdS_4 \times S^2-brane in the bulk AdS_5 \times S^5 which gives rise to a defect conformal field theory (dCFT) in the dual field theory, and the other is a giant graviton system with an open string excitation. In both cases, excitations on open strings attaching to D-branes (a D5-brane for the dCFT case, and a spherical D3-brane for the giant graviton case) can be represented by magnon states in the spin-chains with appropriate boundary conditions, in which informations of the D-branes are encoded. We concentrate on single-magnon problems, and explain how to calculate boundary S-matrices via the PABA technique. We also discuss the energy spectrum in the BMN limit.Comment: 1+24 pages, 1 figure, typos corrected, references added, discussions on the integrability for giant gravitons modified, version to appear in JHE

The narratives of Hardship: : The new and the old poor in the aftermath of the 2008 crisis in Europe

This document is the Accepted Manuscript version of the following article: Hulya Dagdeviren, Matthew Donoghue, and Lars Meier, ‘The narratives of hardship: the new and the old poor in the aftermath of the 2008 crisis in Europe’, The Sociological Review, vol. 65 (2): 369-385, May 2017. The final, definitive version of record is available online at doi: https://doi.org/10.1111/1467-954X.12403. Published by SAGE.This paper examines poverty and hardship in Europe after the 2008 crisis, using household interviews in nine European countries. A number of findings deserve highlighting. First, making a distinction between ‘the old poor’ (those who lived in poverty before as well as after the crisis) and ‘the new poor’ (thosewho fell into hardship after the crisis), we show that hardship is experienced quite differently by these groups. Second, the household narratives showed that while material deprivations constitute an important aspect of hardship, the themes of insecurity and dependency also emerged as fundamental dimensions. In contrast to popular political discourse in countries such as the UK, dependency on welfare or family was experienced as a source of distress and manifested as a form of hardship by participants in all countries covered in this study.Peer reviewedFinal Accepted Versio

Asymptotic Bethe Ansatz S-matrix and Landau-Lifshitz type effective 2-d actions

Motivated by the desire to relate Bethe ansatz equations for anomalous dimensions found on the gauge theory side of the AdS/CFT correspondence to superstring theory on AdS_5 x S5 we explore a connection between the asymptotic S-matrix that enters the Bethe ansatz and an effective two-dimensional quantum field theory. The latter generalizes the standard ``non-relativistic'' Landau-Lifshitz (LL) model describing low-energy modes of ferromagnetic Heisenberg spin chain and should be related to a limit of superstring effective action. We find the exact form of the quartic interaction terms in the generalized LL type action whose quantum S-matrix matches the low-energy limit of the asymptotic S-matrix of the spin chain of Beisert, Dippel and Staudacher (BDS). This generalises to all orders in the `t Hooft coupling an earlier computation of Klose and Zarembo of the S-matrix of the standard LL model. We also consider a generalization to the case when the spin chain S-matrix contains an extra ``string'' phase and determine the exact form of the LL 4-vertex corresponding to the low-energy limit of the ansatz of Arutyunov, Frolov and Staudacher (AFS). We explain the relation between the resulting ``non-relativistic'' non-local action and the second-derivative string sigma model. We comment on modifications introduced by strong-coupling corrections to the AFS phase. We mostly discuss the SU(2) sector but also present generalizations to the SL(2) and SU(1|1) sectors, confirming universality of the dressing phase contribution by matching the low-energy limit of the AFS-type spin chain S-matrix with tree-level string-theory S-matrix.Comment: 52 pages, 4 figures, Imperial-TP-AT-6-2; v2: new sections 7.3 and 7.4 computing string tree-level S-matrix in SL(2) and SU(1|1) sectors, references adde