5,906 research outputs found
F-theory at order
We study the effective physics of F-theory at order in derivative
expansion. We show that the ten-dimensional type IIB eight-derivative couplings
involving the graviton and the axio-dilaton naturally descend from pure gravity
in twelve dimensions. Upon compactification on elliptically fibered Calabi-Yau
fourfolds, the non-trivial vacuum profile for the axio-dilaton leads to a new,
genuinely N=1, correction to the four-dimensional effective action.Comment: 24 pages, minor improvements, typos correcte
The effective action of warped M-theory reductions with higher-derivative terms - Part II
We study the three-dimensional effective action obtained by reducing
eleven-dimensional supergravity with higher-derivative terms on a background
solution including a warp-factor, an eight-dimensional compact manifold, and
fluxes. The dynamical fields are K\"ahler deformations and vectors from the
M-theory three-form. We show that the potential is only induced by fluxes and
the naive contributions obtained from higher-curvature terms on a Calabi-Yau
background vanish once the back-reaction to the full solution is taken into
account. For the resulting three-dimensional action we analyse the K\"ahler
potential and complex coordinates and show compatibility with N=2
supersymmetry. We argue that the higher-order result is also compatible with a
no-scale condition. We find that the complex coordinates should be formulated
as divisor integrals for which a non-trivial interplay between the warp-factor
terms and the higher-curvature terms allow a derivation of the moduli space
metric. This leads us to discuss higher-derivative corrections to the M5-brane
action.Comment: 26 page
Non-Supersymmetric F-Theory Compactifications on Spin(7) Manifolds
We propose a novel approach to obtain non-supersymmetric four-dimensional
effective actions by considering F-theory on manifolds with special holonomy
Spin(7). To perform such studies we suggest that a duality relating M-theory on
a certain class of Spin(7) manifolds with F-theory on the same manifolds times
an interval exists. The Spin(7) geometries under consideration are constructed
as quotients of elliptically fibered Calabi-Yau fourfolds by an
anti-holomorphic and isometric involution. The three-dimensional minimally
supersymmetric effective action of M-theory on a general Spin(7) manifold with
fluxes is determined and specialized to the aforementioned geometries. This
effective theory is compared with an interval Kaluza-Klein reduction of a
non-supersymmetric four-dimensional theory with definite boundary conditions
for all fields. Using this strategy a minimal set of couplings of the
four-dimensional low-energy effective actions is obtained in terms of the
Spin(7) geometric data. We also discuss briefly the string interpretation in
the Type IIB weak coupling limit.Comment: 39 pages, 4 figures, v2: improvements and clarifications on the 4d
interpretation and weak coupling limit; typos correcte
On M-theory fourfold vacua with higher curvature terms
We study solutions to the eleven-dimensional supergravity action, including
terms quartic and cubic in the Riemann curvature, that admit an
eight-dimensional compact space. The internal background is found to be a
conformally Kahler manifold with vanishing first Chern class. The metric
solution, however, is non-Ricci-flat even when allowing for a conformal
rescaling including the warp factor. This deviation is due to the possible
non-harmonicity of the third Chern-form in the leading order Ricci-flat metric.
We present a systematic derivation of the background solution by solving the
Killing spinor conditions including higher curvature terms. These are
translated into first-order differential equations for a globally defined real
two-form and complex four-form on the fourfold. We comment on the supersymmetry
properties of the described solutions.Comment: 14 page
F-Theory on Spin(7) Manifolds: Weak-Coupling Limit
F-theory on appropriately fibered Spin(7) holonomy manifolds is defined to
arise as the dual of M-theory on the same space in the limit of a shrinking
fiber. A class of Spin(7) orbifolds can be constructed as quotients of
elliptically fibered Calabi-Yau fourfolds by an anti-holomorphic involution.
The F-theory dual then exhibits one macroscopic dimension that has the topology
of an interval. In this work we study the weak-coupling limit of a subclass of
such constructions and identify the objects that arise in this limit. On the
Type IIB side we find space-time filling O7-planes as well as O5-planes and
orbifold five-planes with a (-1)^{F_L} factor localised on the interval
boundaries. These orbifold planes are referred to as X5-planes and are S-dual
to a D5-O5 system. For other involutions exotic O3-planes and X3-planes on top
of a six-dimensional orbifold singularity can appear. We show that the objects
present preserve a mutual supersymmetry of four supercharges in the bulk of the
interval and two supercharges on the boundary. It follows that in the
infinite-interval and weak-coupling limit full four-dimensional N=1
supersymmetry is restored, which on the Type IIA side corresponds to an
enhancement of supersymmetry by winding modes in the vanishing interval limit.Comment: 23 page
Generation of internal stress and its effects
Internal stresses may be generated continually in many polycrystalline materials. Their existence is manifested by changes in crystal defect concentration and arrangement, by surface observations, by macroscopic shape changes and particularly by alteration of mechanical properties when external stresses are simultaneously imposed
Understanding jumping to conclusions in patients with persecutory delusions: working memory and intolerance of uncertainty
Background. Persecutory delusions are a key psychotic experience. A reasoning style known as ‘jumping to conclusions’ (JTC) – limited information gathering before reaching certainty in decision making – has been identified as a contributory factor in the occurrence of delusions. The cognitive processes that underpin JTC need to be determined in order to develop effective interventions for delusions. In the current study two alternative perspectives were tested: that JTC partially results from impairment in information-processing capabilities and that JTC is a motivated strategy to avoid uncertainty.Method. A group of 123 patients with persistent persecutory delusions completed assessments of JTC (the 60:40 beads task), IQ, working memory, intolerance of uncertainty, and psychiatric symptoms. Patients showing JTC were compared with patients not showing JTC.Results. A total of 30 (24%) patients with delusions showed JTC. There were no differences between patients who did and did not jump to conclusions in overall psychopathology. Patients who jumped to conclusions had poorer working memory performance, lower IQ, lower intolerance of uncertainty and lower levels of worry.Working memory and worry independently predicted the presence of JTC.Conclusions. Hasty decision making in patients with delusions may partly arise from difficulties in keeping information in mind. Interventions for JTC are likely to benefit from addressing working memory performance, while in vivo techniques for patients with delusions will benefit from limiting the demands on working memory. The study provides little evidence for a contribution to JTC from top down motivational beliefs about uncertainty
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