Domain Walls with Strings Attached

We have constructed a bulk & brane action of IIA theory which describes a pair of BPS domain walls on S_1/Z_2, with strings attached. The walls are given by two orientifold O8-planes with coincident D8-branes and `F1-D0'-strings are stretched between the walls. This static configuration satisfies all matching conditions for the string and domain wall sources and has 1/4 of unbroken supersymmetry.Comment: 12 pages, JHE

Geometric Model for Complex Non-Kaehler Manifolds with SU(3) Structure

For a given complex n-fold M we present an explicit construction of all complex (n+1)-folds which are principal holomorphic T2-fibrations over M. For physical applications we consider the case of M being a Calabi-Yau 2-fold. We show that for such M, there is a subclass of the 3-folds that we construct, which has natural families of non-Kaehler SU(3)-structures satisfying the conditions for N = 1 supersymmetry in the heterotic string theory compactified on the 3-folds. We present examples in the aforementioned subclass with M being a K3-surface and a 4-torus.Comment: LaTeX, 17 pages, organization of the paper was changed, typos correcte

Roulette Inflation with K\"ahler Moduli and their Axions

We study 2-field inflation models based on the ``large-volume'' flux compactification of type IIB string theory. The role of the inflaton is played by a K\"ahler modulus \tau corresponding to a 4-cycle volume and its axionic partner \theta. The freedom associated with the choice of Calabi Yau manifold and the non-perturbative effects defining the potential V(\tau, \theta) and kinetic parameters of the moduli bring an unavoidable statistical element to theory prior probabilities within the low energy landscape. The further randomness of (\tau, \theta) initial conditions allows for a large ensemble of trajectories. Features in the ensemble of histories include ``roulette tractories'', with long-lasting inflations in the direction of the rolling axion, enhanced in number of e-foldings over those restricted to lie in the \tau-trough. Asymptotic flatness of the potential makes possible an eternal stochastic self-reproducing inflation. A wide variety of potentials and inflaton trajectories agree with the cosmic microwave background and large scale structure data. In particular, the observed scalar tilt with weak or no running can be achieved in spite of a nearly critical de Sitter deceleration parameter and consequently a low gravity wave power relative to the scalar curvature power.Comment: Version submitted to Phys.Rev.D. 29 pages, 12 Figures, minor change

Squashed Giants: Bound States of Giant Gravitons

We consider giant gravitons in the maximally supersymmetric type IIB plane-wave, in the presence of a constant NSNS B-field background. We show that in response to the background B-field the giant graviton would take the shape of a deformed three-sphere, the size and shape of which depend on the B-field, and that the giant becomes classically unstable once the B-field is larger than a critical value B_{cr}. In particular, for the B-field which is (anti-)self-dual under the SO(4) isometry of the original giant S^3, the closed string metric is that of a round S^3, while the open string metric is a squashed three-sphere. The squashed giant can be interpreted as a bound state of a spherical three-brane and circular D-strings. We work out the spectrum of geometric fluctuations of the squashed giant and study its stability. We also comment on the gauge theory which lives on the brane (which is generically a noncommutative theory) and a possible dual gauge theory description of the deformed giant.Comment: Latex file, 32 pages, 6 .eps figures; v3: typos correcte

Ground-based station network in Arctic and Subarctic Eurasia : an overview

The international Pan-Eurasian Experiment (PEEX) program addresses the full spectrum of problems related to climate change in Eurasian Northern latitudes. All PEEX activities rely on the bulk of high-quality observational data provided by the ground and marine stations, remote sensing and satellite tools. So far, no coordinated station network has ever existed in Eurasia, moreover, the current scope of relevant research remains largely unknown as no prior assessment has been done to date. This paper makes the first attempt to overview the existing ground station pool in the Arctic-Boreal region with the focus on Russia. The geographical, climatic and ecosystem representativeness of the current stations is discussed, the gaps are identified and tentative station network developments are proposed.Peer reviewe

On Brane Inflation With Volume Stabilization

The distance between BPS branes in string theory corresponds to a flat direction in the effective potential. Small deviations from supersymmetry may lead to a small uplifting of this flat direction and to brane inflation. However, this scenario can work only if the BPS properties of the branes and the corresponding flatness of the inflaton potential are preserved in the theories with the stable volume compactification. We present an ``inflaton trench'' mechanism that keeps the inflaton potential flat due to shift symmetry, which is related to near BPS symmetry in our model.Comment: 12 pages, 2 figure

Hydroclimatic Controls on the Isotopic (δ18 O, δ2 H, d-excess) Traits of Pan-Arctic Summer Rainfall Events

Arctic sea-ice loss is emblematic of an amplified Arctic water cycle and has critical feedback implications for global climate. Stable isotopes (delta O-18, delta H-2, d-excess) are valuable tracers for constraining water cycle and climate processes through space and time. Yet, the paucity of well-resolved Arctic isotope data preclude an empirically derived understanding of the hydrologic changes occurring today, in the deep (geologic) past, and in the future. To address this knowledge gap, the Pan-Arctic Precipitation Isotope Network (PAPIN) was established in 2018 to coordinate precipitation sampling at 19 stations across key tundra, subarctic, maritime, and continental climate zones. Here, we present a first assessment of rainfall samples collected in summer 2018 (n = 281) and combine new isotope and meteorological data with sea ice observations, reanalysis data, and model simulations. Data collectively establish a summer Arctic Meteoric Water Line where delta H-2 = 7.6.delta O-18-1.8 (r(2) = 0.96, p 0.75 parts per thousand/degrees C) were observed at continental sites, while statistically significant temperature relations were generally absent at coastal stations. Model outputs indicate that 68% of the summer precipitating air masses were transported into the Arctic from mid-latitudes and were characterized by relatively high delta O-18 values. Yet 32% of precipitation events, characterized by lower delta O-18 and high d-excess values, derived from northerly air masses transported from the Arctic Ocean and/or its marginal seas, highlighting key emergent oceanic moisture sources as sea ice cover declines. Resolving these processes across broader spatial-temporal scales is an ongoing research priority, and will be key to quantifying the past, present, and future feedbacks of an amplified Arctic water cycle on the global climate system