Evading the Lyth Bound in Hybrid Natural Inflation
Generically, the gravitational-wave or tensor-mode contribution to the primordial curvature spectrum of inflation is tiny if the field-range of the inflaton is much smaller than the Planck scale. We show that this pessimistic conclusion is naturally avoided in a rather broad class of small-field models. More specifically, we consider models where an axion-like shift symmetry keeps the inflaton potential flat (up to non-perturbative cosine-shaped modulations), but inflation nevertheless ends in a waterfall-regime, as is typical for hybrid inflation. In such hybrid natural inflation scenarios (examples are provided by Wilson line inflation and fluxbrane inflation), the slow-roll parameter ǫ can be sizable during an early period (relevant for the CMB spectrum). Subsequently, ǫ quickly becomes very small before the tachyonic instability eventually terminates the slow-roll regime. In this scenario, one naturally generates a considerable tensor-mode contribution in the curvature spectrum, collecting nevertheless the required amount of e-foldings during the final period of inflation. While non-observation of tensors by Planck is certainly not a problem, a discovery in the medium to long term future is realistic.

title: Power Spectrum of Inflationary Attractors
abstract: Inflationary attractors predict the spectral index and tensor-to-scalar ratio to take specific values that are consistent with Planck. An example is the universal attractor for models with a generalised non-minimal coupling, leading to Starobinsky inflation. In this paper we demonstrate that it also predicts a specific relation between the amplitude of the power spectrum and the number of e-folds. The length and height of the inflationary plateau are related via the non-minimal coupling: in a wide variety of examples, the observed power normalisation leads to at least 55 flat e-foldings. Prior to this phase, the inflationary predictions vary and can account for the observational indications of power loss at large angular scales.

title: Lifetime of stringy de Sitter vacua
abstract: In this note we perform a synopsis of the life-times from vacuum decay of several de Sitter vacuum constructions in string/M-theory which have a single dS minimum arising from lifting a pre-existing AdS extremum and no other local minima existent after lifting. For these vacua the decay proceeds via a Coleman-De Luccia instanton towards the universal Minkowski minimum at infinite volume. This can be calculated using the thin-wall approximation, provided the cosmological constant of the local dS minimum is tuned sufficiently small. We compare the estimates for the different model classes and find them all stable in the sense of exponentially long life times as long as they have a very small cosmological constant and a scale of supersymmetry breaking TeV.

title: Hierarchical axion inflation.
abstract: We propose a new field theory mechanism for generating an effective trans-Planckian decay constant from sub-Planckian ones. Using the minimal two axions and a hierarchy between two axion decay constants is sufficient for realizing inflation through nonperturbative effects only and with minimal tuning. The inflationary motion is kept entirely within a sub-Planckian domain. We outline possible strategies of embedding the model in a string theory setup.

title: Study of the neutron quantum states in the gravity field
abstract: We have studied neutron quantum states in the potential well formed by the earth’s gravitational field and a horizontal mirror. The estimated characteristic sizes of the neutron wave functions in the two lowest quantum states correspond to expectations with an experimental accuracy. A position-sensitive neutron detector with an extra-high spatial resolution of $\sim 2 \mathrm{\mu} $m was developed and tested for this particular experiment, to be used to measure the spatial density distribution in a standing neutron wave above a mirror for a set of some of the lowest quantum states. The present experiment can be used to set an upper limit for an additional short-range fundamental force. We studied methodological uncertainties as well as the feasibility of improving further the accuracy of this experiment.

title: Gauge unification in extra dimensions: power corrections vs. higher dimension operators
abstract: Power-like loop corrections to gauge couplings are a generic feature of higher-dimensional field theories. In supersymmetric grand unified theories in d = 5 dimensions, such corrections arise only in the presence of a vacuum expectation value of the adjoint scalar of the gauge multiplet. We show that, using the analysis of the exact quantum effective action by Intriligator, Morrison and Seiberg, these power corrections can be understood as the effect of higher dimension operators. Such operators, both classical and quantum, are highly constrained by gauge symmetry and supersymmetry. As a result, even non-perturbatively large contributions to gauge coupling unification can be unambiguously determined within 5d low-energy effective field theory. Since no massive hypermultiplet matter exists in 6 dimensions, the predictivity is further enhanced by embedding the 5d model in a 6d gauge theory relevant at smaller distances. Thus, large and quantitatively controlled power-law contributions to gauge couplings arise naturally and can, in the most extreme case, lead to calculable TeV-scale power law unification. We identify a simple 5d SU(5) model with one massless 10 in the bulk where the power-law effect is exactly MSSM-like.

title: Nearedge Absorption Spectroscopy of Interplanetary Dust Particles
abstract: Dust Particles (IDPs) are derived from primitive Solar System bodies like asteroids and comets. Studies of IDPs provide a window onto the origins of the solar system and presolar interstellar environments. We are using Total Reflection X-ray Fluorescence (TXRF) techniques developed for the measurement of the cleanliness of silicon wafer surfaces to analyze these particles with high detection sensitivity. In addition to elemental analysis of the particles, we have collected X-ray Absorption Near-Edge spectra in a grazing incidence geometry at the Fe and Ni absorption edges for particles placed on a silicon wafer substrate. We find that the iron is dominated by Fe2O3.

title: Ultrahigh-energy neutrino astrophysics with AMANDA

title: A Fluorescent Aerogel for Capture and Identification of Interplanetary and Interstellar Dust
abstract: Contemporary interstellar dust has never been analyzed in the laboratory, despite its obvious astronomical importance and its potential as a probe of stellar nucleosynthesis and Galactic chemical evolution. Here we report the discovery of a novel fluorescent aerogel that is capable of capturing hypervelocity dust grains and passively recording their kinetic energies. An array of these "calorimetric" aerogel collectors in low-Earth orbit would lead to the capture and identification of large numbers of interstellar dust grains.

title: Observation of muons using the polar ice cap as a Cerenkov detector
abstract: DETECTION of the small flux of extraterrestrial neutrinos expected at energies above 1 TeV, and identification of their astrophysical point sources, will require neutrino telescopes with effective areas measured in square kilometres—much larger than detectors now existing1–3. Such a device can be built only by using some naturally occurring detecting medium of enormous extent: deep Antarctic ice is a strong candidate. A neutrino telescope could be constructed by drilling holes in the ice with hot water into which photomultiplier tubes could be placed to a depth of 1 km. Neutrinos would be recorded, as in underground neutrino detectors using water as the medium, by the observation of Cerenkov radiation from secondary muons. We have begun the AMANDA (Antarctic Muon and Neutrino Detector Array) project to test this idea, and here we describe a pilot experiment using photomultiplier tubes placed into Arctic ice in Greenland. Cerenkov radiation from muons was detected, and a comparison of count rate with the expected muon flux indicates that the ice is very transparent, with an absorption length greater than 18 m. Our results suggest that a full-scale Antarctic ice detector is technically quite feasible.

title: Comparison of the oxidation state of Fe in comet 81P/Wild 2 and chondritic-porous interplanetary dust particles
abstract: Comparison of the oxidation state of Fe in comet 81P/Wild 2 and chondritic-porous interplanetary dust particles R.C. Ogliore a, ⁎ , A.L. Butterworth a , S.C. Fakra b , Z. Gainsforth a , M.A. Marcus b , A.J. Westphal a a b Space Sciences Laboratory, University of California at Berkeley, Berkeley, CA 94720, USA Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA a r t i c l e i n f o a b s t r a c t The fragile structure of chondritic-porous interplanetary dust particles (CP-IDPs) and their minimal parent- body alteration have led researchers to believe these particles originate in comets rather than asteroids where aqueous and thermal alterations have occurred. The solar elemental abundances and atmospheric entry speed of CP-IDPs also suggest a cometary origin. With the return of the Stardust samples from Jupiter- family comet 81P/Wild 2, this hypothesis can be tested. We have measured the Fe oxidation state of 15 CP- IDPs and 194 Stardust fragments using a synchrotron-based x-ray microprobe. We analyzed ∼ 300 ng of Wild 2 material — three orders of magnitude more material than other analyses comparing Wild 2 and CP-IDPs. The Fe oxidation state of these two samples of material are N2σ different: the CP-IDPs are more oxidized than the Wild 2 grains. We conclude that comet Wild 2 contains material that formed at a lower oxygen fugacity than the parent-body, or parent bodies, of CP-IDPs. If all Jupiter-family comets are similar, they do not appear to be consistent with the origin of CP-IDPs. However, comets that formed from a different mix of nebular material and are more oxidized than Wild 2 could be the source of CP-IDPs.  comet 81P/Wild 2 interplanetary dust particles XANES Jupiter-family comets 1.  Chondritic-porous interplanetary dust particles (CP-IDPs), collect- ed in the stratosphere by high-altitude aircraft, are widely thought to originate in comets (Schramm et al., 1989; Bradley, 1994). The collisional history of asteroids makes it unlikely that these particles (fragile, porous aggregates of small grains) are asteroidal (Brownlee, 1985). The atmospheric entry speed of CP-IDPs, as deduced from thermal release proﬁles of solar wind He (Nier and Schlutter, 1992), is consistent with cometary, rather than asteroidal, orbits (Brownlee et al., 1995). Infrared and electron beam studies of IDPs show that those consisting of mostly anhydrous minerals are usually chondritic- porous, whereas IDPs rich in phyllosilicates are usually chondritic- smooth (Sandford and Walker, 1985; Bradley and Brownlee, 1986). The presence of GEMS (glass with embedded metal and sulﬁdes) in IDPs indicates a lack of thermal alteration (Bradley, 1994). CP-IDPs, therefore, show very little parent-body alteration and must originate from either anhydrous objects or hydrous objects that have been kept at very low temperature — again, consistent with cometary origin. Nevertheless, a cometary origin of CP-IDPs is not universally accepted (Flynn, 1992; Thomas et al., 1995). With the return of samples from comet 81P/Wild 2 by NASA's Stardust mission (Brownlee et al., 2006), it is now possible to compare CP-IDPs with material from this Jupiter- ⁎ Corresponding author. E-mail address: ogliore@ssl.berkeley.edu (R.C. Ogliore). family comet. We seek to prove or disprove, with a known level of conﬁdence, the hypothesis that CP-IDPs originate from parent bodies with the composition of comet Wild 2. The oxidation state of Fe is a clear mineralogic indicator of the oxidation state of meteorites (Rubin et al., 1988). Meteorite groups are in fact distinguished from each other by their differing Fe oxidation states, as Urey and Craig ﬁrst reported more than ﬁfty years ago (Urey and Craig, 1953). Parent-body processing can drastically change the Fe oxidation state of some of the meteorite groups, obscuring information about the original oxidation state the material acquired in the solar nebula (Rubin et al., 1988). Carbonates and Fe-bearing crystalline silicates, possible products of aqueous alteration on asteroids (Krot et al., 1995), are found alongside anhydrous minerals in the same Stardust track (Flynn, 2008), and therefore co-existed in one large aggregate in comet Wild 2. No phyllosilicates have been unambiguously identiﬁed in the Stardust samples (Zolensky et al., 2008). With these and other pieces of evidence, Wooden (2008) argues that instead of selective aqueous alteration on submicron scales in the comet itself, grains which formed in different regions of the solar nebula under varying reduction–oxidation conditions (e.g. Mg- and Fe-rich crystalline silicates) migrated, aggregated, and formed comet Wild 2. Likewise, the oxidation state of anhydrous CP-IDPs was unaffected by parent- body processing (Schramm et al., 1989; Zolensky and Thomas, 1995), so a comparison of the Fe oxidation state of comet Wild 2 with anhydrous CP-IDPs yields insight into the nebular environment in which they formed.