Italy’s constitutional referendum: yet another reform to improve the country’s governability

Italy will hold a constitutional referendum on 20-21 September which proposes to reduce the size of both chambers of the Italian parliament. Matthew E. Bergman provides the background to the vote and assesses the potential political consequences

What the manifestos tell us about the 2021 Dutch general election

The Netherlands will hold a general election on 17 March. Matthew E Bergman presents a comprehensive analysis of what the main parties’ manifestos indicate about the country’s current electoral dynamics

Austria's election: four things to know about the result

Austria's legislative election, held on 15 October, saw the Austrian People's Party, led by Sebastian Kurz, emerge as the largest party. Manès Weisskircher and Matthew E. Bergman highlight four things worth knowing about the results of an election that might not only be a game changer for Austrian politics, but which also reflected some of the key political developments in contemporary Western Europe

Party and leadership effects on referendum voting. The Italian 2020 constitutional referendum

Unlike other ballots, referendums do not provide voters a list of parties or candidates to choose from. Here we argue that referendum voting behaviour, however, can be understood through the lends of partisanship and the socio-economic context during the voting period. The personalisation of contemporary politics would also suggest an important role of political leadership in swaying voting decisions. The article applies this theory in analysis of the vote YES of the 2020 Italian Constitutional Referendum. We attribute the success of the 2020 referendum to the role of partisanship, leader favorability, systemic and elite discontent, and the role that interest played in voting decision. Exploring the role that party leaders may have in the voting behaviour on referenda is an area for future research, especially in an era of the presidentialized political parties

Do Nondomestic Undergraduates Choose a Major Field In Order to Maximize Grade Point Averages?

The authors investigated whether undergraduates attending an American West Coast public university who were not U.S. citizens (nondomestic) maximized their grade point averages (GPA) through their choice of major field. Multiple regression hierarchical linear modeling analyses showed that major field’s effect size was small for these undergraduates’ academic marks in mandatory English writing classes and their term GPAs in the five most recent academic years. Engineering and economics, but not science, were significant predictors of writing marks. Economics, but not engineering or science, was a significant predictor of GPAs

Quantum Hall Effect in a Holographic Model

We consider a holographic description of a system of strongly coupled fermions in 2+1 dimensions based on a D7-brane probe in the background of D3-branes, and construct stable embeddings by turning on worldvolume fluxes. We study the system at finite temperature and charge density, and in the presence of a background magnetic field. We show that Minkowski-like embeddings that terminate above the horizon describe a family of quantum Hall states with filling fractions that are parameterized by a single discrete parameter. The quantization of the Hall conductivity is a direct consequence of the topological quantization of the fluxes. When the magnetic field is varied relative to the charge density away from these discrete filling fractions, the embeddings deform continuously into black-hole-like embeddings that enter the horizon and that describe metallic states. We also study the thermodynamics of this system and show that there is a first order phase transition at a critical temperature from the quantum Hall state to the metallic state.Comment: v2: 27 pages, 12 figures. There is a major revision in the quantitative analysis. The qualitative results and conclusions are unchanged, with one exception: we show that the quantum Hall state embeddings, which exist for discrete values of the filling fraction, deform continuously into metallic state embeddings away from these filling fraction

Holographic Nuclear Physics

We analyze the phases of the Sakai-Sugimoto model at finite temperature and baryon chemical potential. Baryonic matter is represented either by 4-branes in the 8-branes or by strings stretched from the 8-branes to the horizon. We find the explicit configurations and use them to determine the phase diagram and equation of state of the model. The 4-brane configuration (nuclear matter) is always preferred to the string configuration (quark matter), and the latter is also unstable to density fluctuations. In the deconfined phase the phase diagram has three regions corresponding to the vacuum, quark-gluon plasma, and nuclear matter, with a first-order and a second-order phase transition separating the phases. We find that for a large baryon number density, and at low temperatures, the dominant phase has broken chiral symmetry. This is in qualitative agreement with studies of QCD at high density.Comment: 27 pages, 26 figures. v2: Added a comment about higher derivative corrections to the DBI action in the smeared instanton in section 2.1. v3: References added, version published in JHEP. v4: misprints correcte

Striped instability of a holographic Fermi-like liquid

We consider a holographic description of a system of strongly-coupled fermions in 2+1 dimensions based on a D7-brane probe in the background of D3-branes. The black hole embedding represents a Fermi-like liquid. We study the excitations of the Fermi liquid system. Above a critical density which depends on the temperature, the system becomes unstable towards an inhomogeneous modulated phase which is similar to a charge density and spin wave state. The essence of this instability can be effectively described by a Maxwell-axion theory with a background electric field. We also consider the fate of zero sound at non-zero temperature.Comment: 16 pages, 9 figures; v2: added discussion and one figure. Typos correcte

Fluctuations of a holographic quantum Hall fluid

We analyze the neutral spectrum of the holographic quantum Hall fluid described by the D2-D8' model. As expected for a quantum Hall state, we find the system to be stable and gapped and that, at least over much of the parameter space, the lowest excitation mode is a magneto-roton. In addition, we find magneto-rotons in higher modes as well. We show that these magneto-rotons are direct consequences of level crossings between vector and scalar modes.Comment: 20 pages, 8 figures; v.2 figures improved, 2 figures added, and text clarified particularly in Sec. 5, to appear in JHE

Response of Holographic QCD to Electric and Magnetic Fields

We study the response of the Sakai-Sugimoto holographic model of large N_c QCD at nonzero temperature to external electric and magnetic fields. In the electric case we find a first-order insulator-conductor transition in both the confining and deconfining phases of the model. In the deconfining phase the conductor is described by the parallel 8-brane-anti-8-brane embedding with a current of quarks and anti-quarks. We compute the conductivity and show that it agrees precisely with a computation using the Kubo formula. In the confining phase we propose a new kind of 8-brane embedding, corresponding to a baryonic conductor. In the magnetic field case we show that the critical temperature for chiral-symmetry restoration in the deconfined phase increases with the field and approaches a finite value in the limit of an infinite magnetic field. We also illustrate the nonlinear behavior of the electric and magnetic susceptibilities in the different phases.Comment: 18 pages, 19 figures; reference added, version published in JHE