119580851
Supergravity as generalised geometry I: type II theories
A bstractWe reformulate ten-dimensional type II supergravity as a generalised geometrical analogue of Einstein gravity, defined by an O(9, 1) × O(1, 9) ⊂ O(10, 10) × $ {\mathbb{R}^{+} } $ structure on the generalised tangent space. Using the notion of generalised connection and torsion, we introduce the analogue of the Levi-Civita connection, and derive the corresponding tensorial measures of generalised curvature. We show how, to leading order in the fermion fields, these structures allow one to rewrite the action, equations of motion and supersymmetry variations in a simple, manifestly Spin(9, 1) × Spin(1, 9)-covariant form. The same formalism also describes d-dimensional compactifications to flat space.
119170433
Supersymmetric Backgrounds and Generalised Special Holonomy
We define intrinsic torsion in generalised geometry and use it to introduce a new notion of generalised special holonomy. We then consider generic warped supersymmetric flux compactifications of M theory and Type II of the form $\mathbb{R}^{D-1,1}\times M$. Using the language of $E_{d(d)}\times\mathbb{R}^+$ generalised geometry, we show that, for $D\geq 4$, preserving minimal supersymmetry is equivalent to the manifold $M$ having generalised special holonomy and list the relevant holonomy groups. We conjecture that this result extends to backgrounds preserving any number of supersymmetries. As a prime example, we consider $\mathcal{N}=1$ in $D=4$. The corresponding generalised special holonomy group is $SU(7)$, giving the natural M theory extension to the notion of a $G_2$ manifold, and, for Type II backgrounds, reformulating the pure spinor $SU(3)\times SU(3)$ conditions as an integrable structure.
53392067
Generalised geometry for string corrections
A bstractWe present a general formalism for incorporating the string corrections in generalised geometry, which necessitates the extension of the generalised tangent bundle. Not only are such extensions obstructed, string symmetries and the existence of a welldefined effective action require a precise choice of the (generalised) connection. The action takes a universal form given by a generalised Lichnerowitz-Bismut theorem. As examples of this construction we discuss the corrections linear in α′ in heterotic strings and the absence of such corrections for type II theories.
119264399
Supergravity as Generalised Geometry II: $E_{d(d)} \times \mathbb{R}^+$ and M theory
We reformulate eleven-dimensional supergravity, including fermions, in terms of generalised geometry, for spacetimes that are warped products of Minkowski space with a $d$-dimensional manifold $M$ with $d\leq7$. The reformation has a $E_{d(d)} \times \mathbb{R}^+$ structure group and is has a local $\tilde{H}_d$ symmetry, where $\tilde{H}_d$ is the double cover of the maximally compact subgroup of $E_{d(d)}$. The bosonic degrees for freedom unify into a generalised metric, and, defining the generalised analogue $D$ of the Levi-Civita connection, one finds that the corresponding equations of motion are the vanishing of the generalised Ricci tensor. To leading order, we show that the fermionic equations of motion, action and supersymmetry variations can all be written in terms of $D$. Although we will not give the detailed decompositions, this reformulation is equally applicable to type IIA or IIB supergravity restricted to a $(d-1)$-dimensional manifold. For completeness we give explicit expressions in terms of $\tilde{H}_4=\mathit{Spin}(5)$ and $\tilde{H}_7=\mathit{SU}(8)$ representations for $d=4$ and $d=7$.
118454147
First observation of liquid-xenon proportional electroluminescence in THGEM holes
Radiation-induced proportional-electroluminescence UV signals, emitted from the holes of a Thick Gas Electron Multiplier (THGEM) electrode immersed in liquid xenon, were recorded with a PMT for the first time. Significant photon yields were observed with gamma photons and alpha particles using a 0.4 mm thick electrode with 0.3 mm diameter holes; at 2 kV across the THGEM the photon yield was estimated to be ~ 600 UV photons/electron over 4π. This may pave the way towards the realization of novel single-phase noble-liquid radiation detectors incorporating liquid hole-multipliers (LHM); their concept is presented.
119971815
First results with THGEM followed by submillimetric multiplying gap
This work presents the first results dealing with THGEMs coupled to submillimetric multiplication gaps, operated in an atmospheric pressure of Ne/CF4. The experimental studies done so far with a THGEM coupled to submillimetric multiplication gaps achieved charge-gains of 4 × 104 and 1 × 105 in Ne/CF4 (95:5), for 0.4 mm and 0.8 mm gaps, respectively, values that are one order of magnitude higher than those obtained in single-THGEM configuration and approximately half from those obtained for a cascaded-THGEM configuration. The present studies evaluate the performance operation in terms of the charge-gain characteristics and X-ray energy resolution.