118008749
AMANDA: Antarctic Muon And Neutrino Detector Array
Enormous detectors with unprecedented sensitivity will be required to search for astrophysical sources of neutrinos. If the transparency of deep polar ice is similar to that measured in the laboratory, then AMANDA (Antarctic Muon And Neutrino Detector Array) may be the most cost-effective way to reach the detector volumes required to search for astrophysical sources of high energy neutrinos or WIMP annihilation within the sun.
119462460
Probing the structure of the cold dark matter halo using ancient mica
Mica can store (for {gt}1thinspGyr) etchable tracks caused by atoms recoiling from WIMPs. Ancient mica is a directional detector despite the complex motions it makes with respect to the WIMP {open_quotes}wind.{close_quotes} We can exploit the properties of directionality and long integration time to probe for structure in the dark matter halo of our galaxy. We compute a sample of possible signals in mica for a plausible model of halo structure. {copyright} {ital 1998} {ital The American Physical Society}
55672053
Comparison of the oxidation state of Fe in comet 81P/Wild 2 and chondritic-porous interplanetary dust particles
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. Keywords: comet 81P/Wild 2 interplanetary dust particles XANES Jupiter-family comets 1. Introduction 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.
12149567
Formation of GEMS from shock-accelerated crystalline dust in superbubbles
Interplanetary dust particles (IDPs) contain enigmatic sub-micron components called GEMS (Glass with Embedded Metal and Sulfides). The compositions and structures of GEMS indicate that they have been processed by exposure to ion- izing radiation but details of the actual irradiation environment(s) have remained elusive. Here we propose a mechanism and astrophysical site for GEMS formation that explains for the first time the following key properties of GEMS; they are stoichiometrically enriched in oxygen and systematically deple- ted in S, Mg, Ca and Fe (relative to solar abundances), most have normal (solar) oxygen isotopic compositions, they exhibit a strikingly narrow size distribution (0.1-0.5 $\mu$m diameter), and some of them contain ``relict'' crystals within their glass matrices. We show that these properties are incon- sistent with amorphization by particles accelerated by diffusive shock accel- eration. Instead, we propose that GEMS are formed from crystalline grains that condense in outflows from massive stars in OB associations, are accelerated in encounters with frequent supernova shocks inside the associated superbubble, and are implanted with atoms from the hot gas in the SB interior. We thus rev- erse the usual roles of target and projectile. Rather than being bombarded at rest by energetic ions, grains are accelerated and bombarded by a nearly mono- velocity beam of atoms as viewed in their rest frame. Meyer, Drury and Ellison have proposed that galactic cosmic rays originate from ions sputtered from such accelerated dust grains. We suggest that GEMS are surviving members of a pop- ulation of fast grains that constitute the long-sought source material for gal- actic cosmic rays. Thus, representatives of the GCR source material may have been awaiting discovery in cosmic dust labs for the last thirty years.
119295369
The powers of monodromy
A bstractFlux couplings to string theory axions yield super-Planckian field ranges along which the axion potential energy grows. At the same time, other aspects of the physics remain essentially unchanged along these large displacements, respecting a discrete shift symmetry with a sub-Planckian period. After a general overview of this monodromy effect and its application to large-field inflation, we present new classes of specific models of monodromy inflation, with monomial potentials μ4−pϕp. A key simplification in these models is that the inflaton potential energy plays a leading role in moduli stabilization during inflation. The resulting inflaton-dependent shifts in the moduli fields lead to an effective flattening of the inflaton potential, i.e. a reduction of the exponent from a fiducial value p0 to p < p0. We focus on examples arising in compactifications of type IIB string theory on products of tori or Riemann surfaces, where the inflaton descends from the NS-NS two-form potential B2, with monodromy induced by a coupling to the R-R field strength F1. In this setting we exhibit models with p = 2/3, 4/3, 2, and 3, corresponding to predictions for the tensor-to-scalar ratio of r ≈ 0.04, 0.09, 0.13, and 0.2, respectively. Using mirror symmetry, we also motivate a second class of examples with the role of the axions played by the real parts of complex structure moduli, with fluxes inducing monodromy.
44699983
Quantum motion of a neutron in a waveguide in the gravitational field
We study theoretically the quantum motion of a neutron in a horizontal waveguide in the gravitational field of the Earth. The waveguide in question is equipped with a mirror below and a rough surface absorber above. We show that such a system acts as a quantum filter, i.e. it effectively absorbs quantum states with sufficiently high transversal energy but transmits low-energy states. The states transmitted are determined mainly by the potential well formed by the gravitational field of the Earth and the mirror. The formalism developed for quantum motion in an absorbing waveguide is applied to the description of the recent experiment on the observation of the quantum states of neutrons in the Earth's gravitational field.
8423738
Consistent de Sitter string vacua from Kahler stabilization and D-term uplifting
In this note, we review our construction of de Sitter vacua in type IIB flux compactifications, in which moduli stabilization and D-term uplifting can be combined consistently with the supergravity constraints. Here, the closed string fluxes fix the dilaton and the complex structure moduli while perturbative quantum corrections to the Kahler potential stabilize the volume Kahler modulus in an AdS4-vacuum. Then, magnetized D7-branes provide consistent supersymmetric D-term uplifting towards dS4. Based on hep-th/0602253.
122358531
Reply to “Comment on ‘Measurement of quantum states of neutrons in the Earth’s gravitational field’ ”
Possible false effects in the experiment on the measurement of quantum states of neutrons in the Earth's gravitational field are discussed. It is shown that the measured quantum states are defined mainly by a mirror and the gravitational field.
15943987
De Sitter string vacua from perturbative Kähler corrections and consistent D-terms
We present a new way to construct de Sitter vacua in type IIB flux compactifications, in which moduli stabilization and D-term uplifting can be combined in a manner consistent with the supergravity constraints. Here, the closed string fluxes fix the dilaton and the complex structure moduli while perturbative quantum corrections to the Kahler potential stabilize the volume Kahler modulus in an AdS4-vacuum. Then, the presence of magnetized D7-branes in this setup provide supersymmetric D-terms in a fully consistent way which uplift the AdS4-vacuum to a metastable dS-minimum.