13,808 research outputs found
Quantum Evolution of Inhomogeneities in Curved Space
We obtain the renormalized equations of motion for matter and semi-classical
gravity in an inhomogeneous space-time. We use the functional Schrodinger
picture and a simple Gaussian approximation to analyze the time evolution of
the model, and we establish the renormalizability of this
non-perturbative approximation. We also show that the energy-momentum tensor in
this approximation is finite once we consider the usual mass and coupling
constant renormalizations, without the need of further geometrical
counter-terms.Comment: 22 page
On the presence of mid-gap states in CaV4O9
Using exact diagonalizations of finite clusters with up to 32 sites, we study
the model on the 1/5 depleted square lattice. Spin-spin correlation
functions are consistent with plaquette order in the spin gap phase which
exists for intermediate values of . Besides, we show that singlet
states will be present in the singlet-triplet gap if is not too small
(). We argue that this property should play a central
role in determining the exchange integrals in Comment: 4 pages, 5 postscript figure
Who fakes support for the military? Experimental evidence from Tunisia
Surveys around the world report exceptionally high levels of support for the military. This is particularly relevant for countries in transition from authoritarian rule to democracy, where militaries can play a vital role for democratic consolidation or autocratic backsliding. Given the sensitive nature of the issue, we suspect that figures indicating strong support for the military are at least partly driven by sensitivity bias. We explore this possibility through list experiments in two nationally representative surveys in Tunisia. We find that misreporting of support for the military in Tunisia is substantial, with respondents overreporting positive attitudes by 40–50 percentage points. Moreover, misreporting is not random, but instead varies systematically by incumbency, with supporters of governing parties misreporting support for the military to a significantly higher degree than opposition supporters or non-voters. Our results suggest that public opinion researchers should be wary of using direct questions to measure support for the military
Coup Agency and Prospects for Democracy
This research note introduces new global data on military coups. Conventional aggregate data so far have conflated two distinct types of coups. Military interventions by leading officers are coups "from above,"characterized by political power struggles within authoritarian elite coalitions where officers move against civilian elites, executive incumbents, and their loyal security personnel. By contrast, power grabs by officers from the lower and middle ranks are coups "from below,"where military personnel outside of the political elite challenge sitting incumbents, their loyalists, and the regime itself. Disaggregating coup types offers leverage to revise important questions about the causes and consequences of military intervention in politics. This research note illustrates that coup attempts from the top of the military hierarchy are much more likely to be successful than coups from the lower and middle ranks of the military hierarchy. Moreover, coups from the top recalibrate authoritarian elite coalitions and serve to sustain autocratic rule; they rarely produce an opening for a democratic transition. Successful coups from below, by contrast, can result in the breakdown of authoritarian regimes and generate an opening for democratic transitions
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