Codimension-2 brane–bulk matching: examples from six and ten dimensions

We formulate point-particle effective field theory (PPEFT) for relativistic spinhalf fermions interacting with a massive, charged finite-sized source using a first-quantized effective field theory for the heavy compact object and a second-quantized language for the lighter fermion with which it interacts. This description shows how to determine the near-source boundary condition for the Dirac field in terms of the relevant physical properties of the source, and reduces to the standard choices in the limit of a point source. Using a first-quantized effective description is appropriate when the compact object is sufficiently heavy, and is simpler than (though equivalent to) the effective theory that treats the compact source in a second-quantized way. As an application we use the PPEFT to parameterize the leading energy shift for the bound energy levels due to finite-sized source effects in a model-independent way, allowing these effects to be fit in precision measurements. Besides capturing finite-source-size effects, the PPEFT treatment also efficiently captures how other short-distance source interactions can shift bound-state energy levels, such as due to vacuum polarization (through the Uehling potential) or strong interactions for Coulomb bound states of hadrons, or any hypothetical new short-range forces sourced by nuclei.

Section: Rg Evolutionmentioning

confidence: 99%

Point-particle effective field theory III: relativistic fermions and the Dirac equation

Burgess¹,

Hayman²,

Rummel³

et al. 2017

“…Although it remains an unsolved problem as to how this dynamics works in string theory, the effects of on-brane loops [83][84][85][86] and back-reaction [26,27,[87][88][89][90] have been studied for non-supersymmetric, codimension-2 branes in simpler 6D extra-dimensional models. These simpler systems resemble their 10D cousins in that the back-reaction is also competitive with bulk physics in stabilising the extra dimensions, yet doesn't destroy the presence of large-volume solutions.…”

Section: Modulus Spectrum and Couplings: Correctionsmentioning

confidence: 99%

Anisotropic modulus stabilisation: strings at LHC scales with micron-sized extra dimensions

Cicoli

Burgess

Quevedo

2011

151

We construct flux-stabilised Type IIB string compactifications whose extra dimensions have very different sizes, and use these to describe several types of vacua with a TeV string scale. Because we can access regimes where two dimensions are hierarchically larger than the other four, we find examples where two dimensions are micron-sized while the other four are at the weak scale in addition to more standard examples with all six extra dimensions equally large. Besides providing ultraviolet completeness, the phenomenology of these models is richer than vanilla large-dimensional models in several generic ways: (i) they are supersymmetric, with supersymmetry broken at sub-eV scales in the bulk but only nonlinearly realised in the Standard Model sector, leading to no MSSM superpartners for ordinary particles and many more bulk missing-energy channels, as in supersymmetric large extra dimensions (SLED); (ii) small cycles in the more complicated extra-dimensional geometry allow some KK states to reside at TeV scales even if all six extra dimensions are nominally much larger; (iii) a rich spectrum of string and KK states at TeV scales; and (iv) an equally rich spectrum of very light moduli exist having unusually small (but technically natural) masses, with potentially interesting implications for cosmology and astrophysics that nonetheless evade new-force constraints. The hierarchy problem is solved in these models because the extra-dimensional volume is naturally stabilised at exponentially large values: the extra dimensions are Calabi-Yau geometries with a 4D K3 or T 4 -fibration over a Open Access doi:10.1007/JHEP10 (2011)119 JHEP10 (2011)119 2D base, with moduli stabilised within the well-established LARGE-Volume scenario. The new technical step is the use of poly-instanton corrections to the superpotential (which, unlike for simpler models, are likely to be present on K3 or T 4 -fibered Calabi-Yau compactifications) to obtain a large hierarchy between the sizes of different dimensions. For several scenarios we identify the low-energy spectrum and briefly discuss some of their astrophysical, cosmological and phenomenological implications.

“…The only assumption these solutions make is that neither brane couples directly to the bulk dilaton, φ, and as a result the normal derivative of φ vanishes in the near-brane limit [25,26]. The solutions described here are those of refs.…”

Section: Explicit Solutions For Non-identical Branesmentioning

confidence: 96%

“…This brane action enforces a set of boundary conditions on the bulk fields [25,26], for two calculable nonzero quantities c 1 and c 2 . This condition for supersymmetry is BPS-like, in that some supersymmetries can survive the presence of a brane provided its tension and magnetic 'charge' are related in a particular way.…”

Section: Jhep07(2014)034mentioning

confidence: 99%

See 1 more Smart Citation

Distributed SUSY breaking: dark energy, Newton’s law and the LHC

Burgess

Nierop

Williams

2014

Abstract:We identify the underlying symmetry mechanism that suppresses the lowenergy effective 4D cosmological constant within some 6D supergravity models, generically leading to results suppressed by powers of the KK scale, m 2 KK , relative to the much larger size, m 4 , associated with mass-m particles localized in these models on codimension-2 branes. These models are examples for which the local conditions for unbroken supersymmetry can be satisfied locally everywhere within the extra dimensions, but are obstructed only by global conditions like flux quantization or by the mutual inconsistency of the boundary conditions required at the various branes. Consequently quantities (like vacuum energies) forbidden by supersymmetry cannot become nonzero until wavelengths of order the KK scale are integrated out, since only such long wavelength modes can see the entire space and so 'know' that supersymmetry has broken. We verify these arguments by extending earlier rugby-ball calculations of one-loop vacuum energies within these models to more general pairs of branes within two warped extra dimensions. JHEP07 (2014)034 numerical purposes we take m to be the top-quark mass and take M g as small as possible, consistent with energy-loss bounds from supernovae.) C is a constant depending on the details of the bulk spectrum, which could easily be of order 500 for each of hundreds of fields in the bulk. The value C ∼ 6 × 10 6 would give the observed Dark Energy density.