Supermembrane with Non-Abelilan Gauging and Chern-Simons Quantization

We present non-Abelian gaugings of supermembrane for general isometries for compactifications from eleven-dimensions, starting with Abelian case as a guide. We introduce a super Killing vector in eleven-dimensional superspace for a non-Abelian group G associated with the compact space B for a general compactification, and couple it to a non-Abelian gauge field on the world-volume. As a technical tool, we use teleparallel superspace with no manifest local Lorentz covariance. Interestingly, the coupling constant is quantized for the non-Abelian group G, due to its generally non-trivial mapping \pi_3(G).Comment: 16 pages, no figures. The content has been considerably changed with non-Abelian generalizatio

Modified Gravity via Spontaneous Symmetry Breaking

We construct effective field theories in which gravity is modified via spontaneous breaking of local Lorentz invariance. This is a gravitational analogue of the Higgs mechanism. These theories possess additional graviton modes and modified dispersion relations. They are manifestly well-behaved in the UV and free of discontinuities of the van Dam-Veltman-Zakharov type, ensuring compatibility with standard tests of gravity. They may have important phenomenological effects on large distance scales, offering an alternative to dark energy. For the case in which the symmetry is broken by a vector field with the wrong sign mass term, we identify four massless graviton modes (all with positive-definite norm for a suitable choice of a parameter) and show the absence of the discontinuity.Comment: 5 pages; revised versio

Citizenship:Contrasting Dynamics at the Interface of Integration and Constitutionalism

EUDO Citizenship ObservatoryThis paper explores the different ways in which citizenship has played a role in polity formation in the context of the European Union. It focuses on both the ‘integration’ and the ‘constitution’ dimensions. The paper thus has two substantive sections. The first addresses the role of citizenship of the Union, examining the dynamic relationship between this concept, the role of the Court of Justice, and the free movement dynamic of EU law. The second turns to citizenship in the Union, looking at some recent political developments under which concepts of citizenship, and democratic membership as a key dimension of citizenship, have been given greater prominence. One key finding of the paper is that there is a tension between citizenship of the Union, as part of the EU's ‘old’ incremental constitutionalism based on the constitutionalisation of the existing Treaties, and citizenship in the Union, where the possibilities of a ‘new’ constitutionalism based on renewed constitutional documents have yet to be fully realise

Closed String Field Theory with Dynamical D-brane

We consider a closed string field theory with an arbitrary matter current as a source of the closed string field. We find that the source must satisfy a constraint equation as a consequence of the BRST invariance of the theory. We see that it corresponds to the covariant conservation law for the matter current, and the equation of motion together with this constraint equation determines the classical behavior of both the closed string field and the matter. We then consider the boundary state (D-brane) as an example of a source. We see that the ordinary boundary state cannot be a source of the closed string field when the string coupling g turns on. By perturbative expansion, we derive a recursion relation which represents the bulk backreaction and the D-brane recoil. We also make a comment on the rolling tachyon boundary state.Comment: 30 pages, LaTeX2e, no figures. Typos are correcte

Theory and Phenomenology of Type I strings and M-theory

The physical motivations and the basic construction rules for Type I strings and M-theory compactifications are reviewed in light of the recent developments. The first part contains the basic theoretical ingredients needed for building four-dimensional supersymmetric models, models with broken supersymmetry and for computing low-energy actions and quantum corrections to them. The second part contains some phenomenological applications to brane world scenarios with low values of the string scale and large extra dimensions.Comment: 129 pages, 7 eps figures, LaTeX, version to appear in Class. Quantum Gra