Short Distance Scale Research Articles

EXPLORING TRANS-PLANCKIAN PHYSICS AND THE CURVATURE EFFECT BY THE PRIMORDIAL POWER SPECTRUM WITH WMAP FIVE-YEAR DATA

The vacuum inflation with a boundary condition specified at a short distance scale in a generally primeval nonflat universe, and implications of the correspondingly modified primordial power spectrum via the WMAP data are investigated. We obtain a general form of the modified primordial power spectrum including the effects of both the possibly new physics scale and the spatial curvature. The modulation of the primordial power spectrum due to new physics is of the order H/Λ, where H is the Hubble parameter during inflation and Λ is the new physics scale which is key to inflation, while the modulation from the curvature effect is of the order K/k2, where K is the spatial curvature before inflation and k is the comoving wave number. We also find that a closed universe before inflation is favored by WMAP five-year data.

Searching for New Physics with Rare decays and CP Violation

After an overture and a non-technical exposition of the relevant theoretical framework, that together offer hopefully a grand picture of the present status of flavour physics, I will collect 20 Goals for this important field. Most of them could be reached already in the next decade. Taken together these goals could be considered as a systematic search for New Physics with the help of flavour- and CP-violating decays of K, D, B mesons and leptons. Also electric dipole moments and (g − 2)μ play an important role in this program. In this context we will discuss very briefly several extensions of the Standard Model like models with Minimal Flavour Violation, general MSSM, Littlest Higgs Model with T parity and Randall-Sundrum models. This presentation is not meant to be a comprehensive review of flavour physics but rather a personal view on this fascinating field and an attempt to collect those routes that with the help of oncoming experiments should allow us to reach a much deeper understanding of flavour physics at very short distance scales.

On the shape of a D-brane bound state and its topology change

As is well known, coordinates of D-branes are described by NxN matrices. From generic non-commuting matrices, it is difficult to extract physics, for example, the shape of the distribution of positions of D-branes. To overcome this problem, we generalize and elaborate on a simple prescription, first introduced by Hotta, Nishimura and Tsuchiya, which determines the most appropriate gauge to make the separation between diagonal components (D-brane positions) and off-diagonal components. This prescription makes it possible to extract the distribution of D-branes directly from matrices. We verify the power of it by applying it to Monte-Carlo simulations for various lower dimensional Yang-Mills matrix models. In particular, we detect the topology change of the D-brane bound state for a phase transition of a matrix model; the existence of this phase transition is expected from the gauge/gravity duality, and the pattern of the topology change is strikingly similar to the counterpart in the gravity side, the black hole/black string transition. We also propose a criterion, based on the behavior of the off-diagonal components, which determines when our prescription gives a sensible definition of D-brane positions. We provide numerical evidence that our criterion is satisfied for the typical distance between D-branes. For a supersymmetric model, positions of D-branes can be defined even at a shorter distance scale. The behavior of off-diagonal elements found in this analysis gives some support for previous studies of D-brane bound states.

Low-mass lepton pair production at large transverse momentum

We study the transverse momentum distribution of low-mass lepton pairs produced in hadronic scattering, using the perturbative QCD factorization approach. We argue that the distribution at large transverse momentum, ${Q}_{T}\ensuremath{\gg}Q$, with the pair's invariant mass $Q$ as low as $Q\ensuremath{\sim}{\ensuremath{\Lambda}}_{\mathrm{QCD}}$, can be systematically factorized into universal parton-to-lepton pair fragmentation functions, parton distributions, and perturbatively calculable partonic hard parts evaluated at a short-distance scale $\ensuremath{\sim}\mathcal{O}(1/{Q}_{T})$. We introduce a model for the input lepton pair fragmentation functions at a scale ${\ensuremath{\mu}}_{0}\ensuremath{\sim}1\text{ }\text{ }\mathrm{GeV}$, which are then evolved perturbatively to scales relevant at the Relativistic Heavy Ion Collider. Using the evolved fragmentation functions, we calculate the transverse momentum distributions in hadron-hadron, hadron-nucleus, and nucleus-nucleus collisions at the Relativistic Heavy Ion Collider. We also discuss the sensitivity of the transverse momentum distribution of low-mass lepton pairs to the gluon distribution.

Gel-like behavior in aggrecan assemblies

Aggrecan, a large biological polyelectrolyte molecule with a bottlebrush shape, forms complexes with hyaluronic acid (HA) that provide compressive resistance in cartilage. In solutions of aggrecan alone, the concentration dependence of the osmotic pressure Pi is marked by self-assembly of the molecules into aggregates. When HA is added to the solution at low aggrecan concentration c, the osmotic pressure is reduced, but in the physiological concentration range this trend is reversed. The osmotic modulus c partial differentialPi partial differentialc, which determines load bearing resistance, is enhanced in the HA-containing solutions. Dynamic light scattering (DLS) measurements show that the aggregates behave like microgels and that they become denser as the aggrecan concentration increases. The degree of densification is greatest at large distance scales in the microgels, but decreases at short distance scales. Measurements at higher resolution, involving small angle neutron scattering and small angle x-ray scattering (SAXS), confirm that at length scales shorter than 1000 angstroms, the density is independent of the concentration and that the individual bottlebrushes in the microgels retain their identity. The absence of collective diffusion modes in the relaxation spectrum, measured by DLS and neutron spin echo, corroborates the lack of interpenetration among the aggrecan subunits in the microgel. Complexation with HA modifies the long-range spatial organization of the microgels. Comparison of the scattering pattern of the individual aggrecan molecules obtained from SAXS measurements with that of the complexes measured by DLS shows that the aggrecan-HA structure is denser and is more uniform than the random microgels. This enhanced space-filling property allows higher packing densities to be attained, thus, optimizing resistance to osmotic compression.

Compressional and Shear-Wave Velocity versus Depth Relations for Common Rock Types in Northern California

Abstract This article presents new empirical compressional and shear-wave velocity ( Vp and Vs ) versus depth relationships for the most common rock types in northern California. Vp versus depth relations were developed from borehole, laboratory, seismic refraction and tomography, and density measurements, and were converted to Vs versus depth relations using new empirical relations between Vp and Vs . The relations proposed here account for increasing overburden pressure but not for variations in other factors that can influence velocity over short distance scales, such as lithology, consolidation, induration, porosity, and stratigraphic age. Standard deviations of the misfits predicted by these relations thus provide a measure of the importance of the variability in Vp and Vs caused by these other factors. Because gabbros, greenstones, basalts, and other mafic rocks have a different Vp and Vs relationship than sedimentary and granitic rocks, the differences in Vs between these rock types at depths below 6 or 7 km are generally small. The new relations were used to derive the 2005 U.S. Geological Survey seismic velocity model for northern California employed in the broadband strong motion simulations of the 1989 Loma Prieta and 1906 San Francisco earthquakes; initial tests of the model indicate that the Vp model generally compares favorably to regional seismic tomography models but that the Vp and Vs values proposed for the Franciscan Complex may be about 5% too high.

DISTRIBUTION OF PARASITES AND PATHOLOGIES IN SENTINEL BIVALVES: NOAA STATUS AND TRENDS “MUSSEL WATCH” PROGRAM

The 1995-1998 histopathology data from NOAA's Mussel Watch Program were analyzed to: (1) document the occurrence of parasites and pathologies in sentinel bivalves during the 1995-1998 time period, (2) describe and compare the geographic distribution of these parasites and pathologies between different bivalve species and between different geographic regions, and (3) evaluate trends in parasite taxon richness. Parasite taxon richness was higher in oysters than in mytilids and dreissenids. Parasites having higher prevalences in a given host taxon routinely also had higher infection intensities. When different geographic locations were compared, the same trends occurred much more rarely. Oysters were more heavily infected based on total parasite body burden than mytilids, and the frequency of hosts with at least one parasite was higher. Excluding the numerically-dominant gregarines, however, removed the differential between oysters and mytilids, with the exception of East- coast mytilids that were more frequently parasitized than East-coast oysters. Dreissenids had lower prevalence and infection intensity for all parasites than the other host bivalve taxa. Though cestodes offer a discrepancy, most of the more common oyster parasites were unicellular, whereas most of the more common mytilid parasites were multicellular. On the average, parasite distributional patterns along a stretch of coastline were more often clinal in nature in mytilids, in that prevalence and infection intensity tended to change gradually over relatively large distance scales, and more bounded in nature in oysters, in that prevalence and infection intensity tended to change more sharply over shorter distance scales. Latitudinal trends were diametric opposites on the two northern coasts. More parasites occurred in mytilids from northern bays of the East coast, whereas fewer occurred in mytilids from northern bays of the West coast. Mytilids far exceeded oysters in the incidence of pathologies, including digestive gland and gonadal abnormalities and hemocytic infiltration. On the West coast, the vast majority of these pathologies occurred in mussels of the Mytilus edulis complex rather than M. californianus. All pathologies were more common in mytilids from the northeast coast than in West-coast mytilids. Indeed, discounting the gregarines, northeast coast mytilids combined the highest instances of pathologies with among the highest parasite body burdens of any bivalve taxon and coastal area combination in the Mussel Watch program.

A self-tuning mechanism in (3 + p)d gravity-scalar theory

We present a new type of self-tuning mechanism for ($3+p$)d brane world models in the framework of gravity-scalar theory. This new type of self-tuning mechanism exhibits a remarkable feature. In the limit $g_s \to 0$, $g_s$ being the string coupling, the geometry of bulk spacetime remains virtually unchanged by an introduction of the Standard Model(SM)-brane, and consequently it is virtually unaffected by quantum fluctuations of SM fields with support on the SM-brane. Such a feature can be obtained by introducing Neveu-Schwarz(NS)-brane as a background brane on which our SM-brane is to be set. Indeed, field equations naturally suggest the existence of the background NS-brane. Among the given such models, of the most interest is the case with $\Lambda=0$, where $\Lambda$ represents the bulk cosmological constant. This model contains a pair of coincident branes (of the SM- and the NS-branes), one of which is a codimension-2 brane placed at the origin of 2d transverse space ($\equiv \Sigma_2$), another a codimension-1 brane placed at the edge of $\Sigma_2$. These two branes are (anti) T-duals of each other, and one of them may be identified as our SM-brane plus the background NS-brane. In the presence of the background NS-brane (and in the absence of $\Lambda$), the 2d transverse space $\Sigma_2$ becomes an orbifold $R_2 /Z_n$ with an appropriate deficit angle. But this is only possible if the ($3+p$)d Planck scale $M_{3+p}$ and the string scale $M_s$($\equiv 1/\sqrt{\alpha^{\prime}}$) are of the same order, which accords with the hierarchy assumption \cite{1,2,3} that the electroweak scale $m_{EW}$ is the only short distance scale existing in nature.

The closed string spectrum of [formula omitted] gauge theories in [formula omitted] dimensions

We use lattice techniques to study the closed-string spectrum of SU(N) gauge theories in 2+1 dimensions. We calculate the energies of the lowest lying ∼30 states for strings with lengths between l∼0.45 fm and l∼3 fm, and compare to different theoretical predictions. We obtain unambiguous evidence that the closed-strings are in the universality class of the Nambu–Goto free bosonic string. Moreover, we clearly see that our data can be described by a covariant string theory with a small/moderate correction down to very short distance scales, and possibly on all distance scales at large-N.

Assessment of Ionosphere Spatial Decorrelation for Global Positioning System-Based Aircraft Landing Systems

Ground-based augmentations of the global positioning system demand guaranteed integrity to support aircraft precision approach and landing navigation. To quantitatively evaluate navigation integrity, an aircraft computes vertical and lateral protection levels as position-error bounds using the standard deviation of ionosphere spatial decorrelation. Thus, it is necessary to estimate typical ionospheric gradients for nominal days and to determine an appropriate upper bound to sufficiently cover the differential error due to the ionosphere spatial decorrelation. Both station-pair and time-step methods are used to assess the standard deviation of vertical (or zenith) ionospheric gradients (σ vig ). The station-pair method compares the simultaneous zenith delays from two different reference stations to a single satellite and observes the difference in delay across the known ionosphere pierce point separation. Because these ionosphere pierce point separations limit the observability of the station-pair method, the time-step method is also used to better understand ionospheric gradients at short distance scales (10-40 km). The time-step method compares the ionospheric delay of a single line of sight at one epoch with the delay for the same line of sight at another epoch a short time (a few to tens of minutes) later. This method has the advantage of removing interfrequency bias calibration errors on different satellites and receivers while possibly introducing an estimation error due to temporal ionospheric gradients. The results of this study demonstrate that typical values of σ vig are on the order of 1-3 mm/km for nonstormy ionospheric conditions. As a result, σ vig of 4 mm/km is conservative enough to bound ionosphere spatial decorrelation for nominal days and still leave enough margin for more active days and for non-Gaussian tail behavior.

High resolution vertical distributions of NO<sub>3</sub> and N<sub>2</sub>O<sub>5</sub> through the nocturnal boundary layer

Abstract. The shallow mixing depth and vertical stratification of the lowest levels of the atmosphere at night has implications for the chemistry of nitrogen oxides emitted from the surface. Here we report vertical profiles of NO3, N2O5 and O3 measured from in-situ instruments on a movable carriage on a 300 m tower. The study offers high-resolution (<1 m) vertical distributions of both NO3 and N2O5 and shows that the nocturnal mixing ratios of these compounds vary widely over short vertical distance scales (10 m or less). Furthermore, there are systematic differences in the steady state lifetimes of NO3 and N2O5 and in the partitioning among nitrogen oxides between different near-surface layers. These differences imply that NO3 and N2O5 occupy distinct chemical regimes as a function of altitude, potentially serving as sinks for nitrogen oxides and O3 near the surface but as reservoirs of NOx and O3 aloft.

Modified gravity, dark energy and modified Newtonian dynamics

We propose a class of actions for the spacetime metric that introduce corrections to theEinstein–Hilbert Lagrangian depending on the logarithm of some curvature scalars. Weshow that for some choices of these invariants the vacuum is ghost free at the perturbativelevel and Newtonian gravity is modified below a characteristic acceleration scale given bya0 = cμ, wherec is the speedof light and μ is a parameter of the model that also determines the late-time Hubble constant:H0∼μ. In these models, besides the massless spin two graviton, there is a scalar excitation of thespacetime metric whose mass depends on the background curvature. This dependence issuch that this scalar, although almost massless in vacuum, becomes massive and effectivelydecouples when one gets close to any source and we recover an acceptable weakfield limit at short distances. There is also a (classical) ‘running’ of Newton’sconstant with the distance to the sources and gravity is easily enhanced at largedistances by a large ratio. We comment on the possibility of building a model with aMOND-like Newtonian limit that could explain the rotation curves of galaxies withoutintroducing dark matter using such actions. We also explore briefly the characteristicgravitational phenomenology that these models imply: besides a long distancemodification of gravity they also predict deviations from Newton’s law at shortdistances. This short distance scale depends on the local background curvature ofspacetime, and we find that for experiments on the Earth’s surface it is of order∼0.1 mm, while this distance would be bigger in space where the local curvature is significantlylower.

Nothing's plenty. The vacuum in modern quantum field theory

Abstract In contemporary theories of the structure of matter at very short distance scales, various properties (some of them hypothetical as yet) of the vacuum are of crucial importance. The technical framework for such studies is quantum field theory. The aim of this article is to provide access, for a non-specialist readership, to the physics of the vacuum as presently understood in quantum field theory. To do this, heavy reliance is placed on a fundamental analogy. The basic theoretical entity—the quantum field—is here regarded as analogous to a quantum-mechanical system with (infinitely) many degrees of freedom. A system of interacting quantum fields is then analogous to a complicated system in solid state physics; it can exist in different energy states, namely the ground state and various excited states. The excited states of the field system are characterized by the presence of excitation quanta, which are the particles (electrons, quarks, photons…) of which our material world is composed. In the g...

Higher twists in polarized DIS and the size of the constituent quark

The spontaneous breaking of chiral symmetry implies the presence of a short-distance scale in the QCD vacuum, which phenomenologically may be associated with the size of the constituent quark, $\ensuremath{\rho}\ensuremath{\approx}0.3\text{ }\text{ }\mathrm{fm}$. We discuss the role of this scale in the matrix elements of the twist-4 and 3 quark-gluon operators determining the leading power ($1/{Q}^{2}$)-corrections to the moments of the nucleon spin structure functions. We argue that the flavor-nonsinglet twist-4 matrix element, ${f}_{2}^{u\ensuremath{-}d}$, has a sizable negative value of the order ${\ensuremath{\rho}}^{\ensuremath{-}2}$, due to the presence of sea quarks with virtualities $\ensuremath{\sim}{\ensuremath{\rho}}^{\ensuremath{-}2}$ in the proton wave function. The twist-3 matrix element, ${d}_{2}$, is not related to the scale ${\ensuremath{\rho}}^{\ensuremath{-}2}$. Our arguments support the results of previous calculations of the matrix elements in the instanton vacuum model. We show that this qualitative picture is in agreement with the phenomenological higher-twist correction extracted from an NLO QCD fit to the world data on ${g}_{1}^{p}$ and ${g}_{1}^{n}$, which include recent data from the Jefferson Lab Hall A and COMPASS experiments. We comment on the implications of the short-distance scale $\ensuremath{\rho}$ for quark-hadron duality and the $x$-dependence of higher-twist contributions.

Light-cone sum rules in soft-collinear effective theory

We derive light-cone sum rules (LCSRs) for exclusive B-meson decays into light energetic hadrons from correlation functions within soft-collinear effective theory (SCET). In these sum rules the short-distance scale refers to “hard-collinear” interactions with virtualities of order Λ QCD m b . Hard scales (related to virtualities of order m b 2 ) are integrated out and enter via external coefficient functions in the sum rule. Soft dynamics is encoded in light-cone distribution amplitudes for the B-meson, which describe both the factorizable and non-factorizable contributions to exclusive B-meson decay amplitudes. As an example, we provide a detailed study of the SCET sum rule for the B → π transition form factor at large recoil, including radiative corrections from hard-collinear loop diagrams at first order in the strong coupling constant. We find remarkable conceptual and numerical differences with the heavy-quark limit of the conventional LCSR approach in QCD.

Spectral types and masses of white dwarfs in globular clusters

White dwarfs in globular clusters offer additional possibilities to determine distances and ages of globular clusters, provided their spectral types and masses are known. We therefore started a project to obtain spectra of white dwarfs in the globular clusters NGC 6397 and NGC 6752. All observed white dwarfs show hydrogen-rich spectra and are therefore classified as DA. Analysing the multi-colour photometry of the white dwarfs in NGC 6752 yields an average gravity of = 7.84 and 0.53 as the most probable average mass for globular cluster white dwarfs. Using this average gravity we try to determine independent temperatures by fitting the white dwarf spectra. While the stellar parameters determined from spectroscopy and photometry usually agree within the mutual error bars, the low resolution and S/N of the spectra prevent us from setting constraints stronger than those derived from the photometry alone. For the same reasons the white dwarf spectra obtained for NGC 6397 unfortunately do not provide an independent distance estimate of sufficient accuracy to distinguish between the long and short distance scale for globular clusters.

A new method for the solution of the Schrödinger equation

We present a new method for the solution of the Schrodinger equation applicable to problems of non-perturbative nature. The method works by identifying three different scales in the problem, which then are treated independently: An asymptotic scale, which depends uniquely on the form of the potential at large distances; an intermediate scale, still characterized by an exponential decay of the wave function and, finally, a short distance scale, in which the wave function is sizable. The key feature of our method is the introduction of an arbitrary parameter in the last two scales, which is then used to optimize a perturbative expansion in a suitable parameter. We apply the method to the quantum anharmonic oscillator and find excellent results.

The RR Lyrae Distance to the Draco Dwarf Spheroidal Galaxy

We present the first CCD variability study of the Draco dwarf spheroidal galaxy. The data were obtained with the Fred Lawrence Whipple Observatory 1.2 m telescope on 22 nights, over a period of 10 months, covering a 22' × 22' field centered at α = 17h19m575, δ = 57°50'05'' (J2000.0). The analysis of the BVI images produced 163 variable stars, 146 of which were RR Lyrae: 123 RRab, 16 RRc, 6 RRd, and one RR12. The other variables include a SX Phe star, four anomalous Cepheids, and a field eclipsing binary. Using the short distance scale statistical parallax calibration of Gould & Popowski and 94 RRab stars from our field, we obtain a distance modulus of (m - M)0 = 19.40 ± 0.02 (stat) ± 0.15 (syst) mag for Draco, corresponding to a distance of 75.8 ± 0.7 (stat) ± 5.4 (syst) kpc. By comparing the spread in magnitudes of RRab stars in B, V, and I, we find no evidence for internal dust in the Draco dwarf spheroidal galaxy. The catalog of all variables, as well as their photometry and finding charts, is available electronically via anonymous ftp and the World Wide Web. The complete set of the CCD frames is available upon request.

On the IR/UV mixing and experimental limits on the parameters of canonical noncommutative spacetimes

We investigate some issues that are relevant for the derivation of experimental limits on the parameters of canonical noncommutative spacetimes. By analyzing a simple Wess-Zumino-type model in canonical noncommutative spacetime with soft supersymmetry breaking we explore the implications of ultraviolet supersymmetry on low-energy phenomenology. The fact that new physics in the ultraviolet can modify low-energy predictions affects significantly the derivation of limits on the noncommutativity parameters based on low-energy data. These are, in an appropriate sense here discussed, ``conditional limits''. We also find that some standard techniques for an effective low-energy description of theories with non-locality at short distance scales are only applicable in a regime where theories in canonical noncommutative spacetime lack any predictivity, because of the strong sensitivity to unknown UV physics. It appears useful to combine high-energy data, from astrophysics, with the more readily available low-energy data.

NGC 6822: short period variable stars, stellar population and distance scale

AbstractResults are presented on a study of the short period variable stars in the dwarf irregular galaxy NGC 6822. We observed an almost uniformly populated classical instability strip from the Horizontal Branch up to the Classical Cepheid region. The main goal we achieved from the analysis of the faint sample is the first detection of RR Lyrae stars in this galaxy.