The Eternity Solution to the Problem of Human Freedom and Divine Foreknowledge

In this paper I defend the eternity solution to the problem of human freedom and divine foreknowledge. After motivating the problem, I sketch the basic contours of the eternity solution. I then consider several objections which contend that the eternity solution falsely implies that we have various powers (e.g., to change God’s beliefs, or to affect the past) which, according to the objector, we do not in fact hav

Perturbation Method for Particle-like Solutions of the Einstein-Dirac-Maxwell Equations

The aim of this Note is to prove by a perturbation method the existence of solutions of the coupled Einstein-Dirac-Maxwell equations for a static, spherically symmetric system of two fermions in a singlet spinor state and with the electromagnetic coupling constant $(\frac{e}{m})^2<1$. We show that the nondegenerate solution of Choquard's equation generates a branch of solutions of the Einstein-Dirac-Maxwell equations

Perturbation method for particlelike solutions of Einstein-Dirac equations

The aim of this work is to prove by a perturbation method the existence of solutions of the coupled Einstein-Dirac equations for a static, spherically symmetric system of two fermions in a singlet spinor state. We relate the solutions of our equations to those of the nonlinear Choquard equation and we show that the nondegenerate solution of Choquard's equation generates solutions for Einstein-Dirac equations

Military Burden and the Democracy Puzzle

The Kantian thought had advanced the idea that wars and military expenditure should decrease as long as democracy widens across the World. Historical evidence seems to invalidate this wisdom because frequency of wars is ncreasing over time and a large amount of public resources is still being committed to military spending. This paper contributes to explain this point by considering the effect of polity regimes on the military spending during the period 1880-1938. Indeed, before World War I the more democratic countries spent more for military purposes than autocracies whereas the reverse is true after 1920. This puzzling behaviour is therefore explained by the inconsistent timing between the ability of a state to drain resources by taxation (state fiscal capacity) and the political participation. Thus, the Kantian idea of a democratic and peaceful world seems to hold only for full democracy with large political participation.Military spending, polity regimes, war, political participation

Temperature Dependence of the Vacancy Formation Energy in Solid 4^4He

We studied the thermal effects on the behavior of incommensurate solid $^4$He at low temperatures using the path integral Monte Carlo method. Below a certain temperature, depending on the density and the structure of the crystal, the vacancies delocalize and a finite condensate fraction appears. We calculated the vacancy formation energy as a function of the temperature and observed a behavior compatible with a two-step structure, with a gap of few K appearing at the onset temperature of off-diagonal long-range order. Estimation of the energy cost of creating two vacancies seems to indicate an effective attractive interaction among the vacancies but the large error inherent to its numerical estimation precludes a definitive statement.Comment: Contribution to the Special Issue on "Quantum Crystals": 9 pages, 3 figure

Entanglement structures in qubit systems

Using measures of entanglement such as negativity and tangles we provide a detailed analysis of entanglement structures in pure states of non-interacting qubits. The motivation for this exercise primarily comes from holographic considerations, where entanglement is inextricably linked with the emergence of geometry. We use the qubit systems as toy models to probe the internal structure, and introduce some useful measures involving entanglement negativity to quantify general features of entanglement. In particular, our analysis focuses on various constraints on the pattern of entanglement which are known to be satisfied by holographic sates, such as the saturation of Araki-Lieb inequality (in certain circumstances), and the monogamy of mutual information. We argue that even systems as simple as few non-interacting qubits can be useful laboratories to explore how the emergence of the bulk geometry may be related to quantum information principles.Comment: 55 pages, 23 figures. v2: typos fixed. v3: minor clarifications. published versio

Simulating frustrated antiferromagnets with quadratically driven QED cavities

We propose a class of quantum simulators for antiferromagnetic spin systems, based on coupled photonic cavities in presence of two-photon driving and dissipation. By modeling the coupling between the different cavities through a hopping term with negative amplitude, we solve numerically the quantum master equation governing the dynamics of the open system and determine its non-equilibrium steady state. Under suitable conditions, the steady state can be described in terms of the degenerate ground states of an antiferromagnetic Ising model. When the geometry of the cavity array is incommensurate with the antiferromagnetic coupling, the steady state presents properties which bear full analogy with those typical of the spin liquid phases arising in frustrated magnets

An example of Berglund-H\"ubsch mirror symmetry for a Calabi-Yau complete intersection

We study an example of complete intersection Calabi-Yau threefold due to Libgober and Teitelbaum arXiv:alg-geom/9301001, and verify mirror symmetry at a cohomological level. Direct computations allow us to propose an analogue to the Berglund-H\"ubsch mirror symmetry setup for this example arXiv:hep-th/9201014. We then follow the approach of Krawitz to propose an explicit mirror map arXiv:0906.0796.Comment: 18 pages, 4 table

6d-5d-4d reduction of BPS attractors in flat gauged supergravities

Via a series of Kaluza-Klein (KK) and Scherk-Schwarz (SS) compactifications we relate BPS attractors and their complete (in general non-BPS) flows to a Minkowski vacuum in gauged supergravities with vanishing scalar potential in 4, 5, and 6 dimensions. This way we can look at a class of extremal non-BPS black holes and strings from IIB string theory viewpoint, keeping 4 supercharges on the horizon. Our results imply the existence of a dual 2d N = (0,2) superconformal field theory (SCFT) that originates from a parent N=(4,4) theory living on a D1-D5 system. This is achieved starting from the BPS black string in 6d with an AdS_3xS^3 attractor and taking two different routes to arrive at a 1/2 BPS AdS_2xS^2 attractor of a non-BPS black hole in 4d N=2 flat gauged supergravity. The two inequivalent routes interchange the order of KK reduction on AdS_3 and SS reduction on S^3. We also find the commutator between the two operations after performing a duality transformation: on the level of the theory the result is the exchange of electric with magnetic gaugings; on the level of the solution we find a flip of the quartic invariant I_4 to -I_4.Comment: 20 pages, 2 flow charts; v2 improved discussion and added referenc