119090701
Axion models with high-scale supersymmetry breaking
Abstract Inspired by the possibility of high-scale supersymmetry breaking in the string landscape where the cosmological constant problem and the gauge hierarchy problem can be solved while the strong CP problem is still a challenge for naturalness, we propose a supersymmetric KSVZ axion model with an approximate universal intermediate-scale ( ∼ 10 11  GeV ) supersymmetry breaking. To protect the global Peccei–Quinn (PQ) symmetry against quantum gravitational violation, we consider the gauged discrete Z N PQ symmetry. In our model the axion can be a cold dark matter candidate, and the intermediate supersymmetry breaking scale is directly related to the PQ symmetry breaking scale. Gauge coupling unification can be achieved at about 2.7 × 10 16  GeV . The Higgs mass range is 130 to 160 GeV. We briefly discuss other axion models with high-scale supersymmetry breaking where the stabilization of the axion solution is similar.
1167548
SURFACE FLUX TRANSPORT MODELING FOR SOLAR CYCLES 15-21: EFFECTS OF CYCLE-DEPENDENT TILT ANGLES OF SUNSPOT GROUPS
We model the surface magnetic field and open flux of the Sun from 1913 to 1986 using a surface flux transport model, which includes the observed cycle-to-cycle variation of sunspot group tilts. The model reproduces the empirically derived time evolution of the solar open magnetic flux and the reversal times of the polar fields. We find that both the polar field and the axial dipole moment resulting from this model around cycle minimum correlate with the strength of the following cycle.
37075538
Role of internal gases and creep of Ag in controlling the critical current density of Ag-sheathed Bi2Sr2CaCu2Ox wires
High engineering critical current density JE of > 500 A/mm2 at 20 T and 4.2 K can be regularly achieved in Ag-sheathed multifilamentary Bi2Sr2CaCu2Ox (Bi-2212) round wire when the sample length is several centimeters. However, JE(20 T) in Bi-2212 wires of several meters length, as well as longer pieces wound in coils, rarely exceeds 200 A/mm2. Moreover, long-length wires often exhibit signs of Bi-2212 leakage after melt processing that are rarely found in short, open-end samples. We studied the length dependence of JE of state-of-the-art powder-in-tube (PIT) Bi-2212 wires and gases released by them during melt processing using mass spectroscopy, confirming that JE degradation with length is due to wire swelling produced by high internal gas pressures at elevated temperatures [A. Malagoli et al. Supercond. Sci. Technol. 24, 075016 (2011) and A. Malagoli et al. Supercond. Sci. Technol. 26, 055018 (2013)]. We further modeled the gas transport in Bi-2212 wires and examined the wire expansion at critical stage...
118827473
Limits to solar cycle predictability: Cross-equatorial flux plumes
Context. Within the Babcock-Leighton framework for the solar dynamo, the strength of a cycle is expected to depend on the strength of the dipole moment or net hemispheric flux during the preceding minimum, which depends on how much flux was present in each hemisphere at the start of the previous cycle and how much net magnetic flux was transported across the equator during the cycle. Some of this transport is associated with the random walk of magnetic flux tubes subject to granular and supergranular buffeting, some of it is due to the advection caused by systematic cross-equatorial flows such as those associated with the inflows into active regions, and some crosses the equator during the emergence process. Aims. We aim to determine how much of the cross-equatorial transport is due to small-scale disorganized motions (treated as diffusion) compared with other processes such as emergence flux across the equator. Methods. We measure the cross-equatorial flux transport using Kitt Peak synoptic magnetograms, estimating both the total and diffusive fluxes. Results. Occasionally a large sunspot group, with a large tilt angle emerges crossing the equator, with flux from the two polarities in opposite hemispheres. The largest of these events carry a substantial amount of flux across the equator (compared to the magnetic flux near the poles). We call such events cross-equatorial flux plumes. There are very few such large events during a cycle, which introduces an uncertainty into the determination of the amount of magnetic flux transported across the equator in any particular cycle. As the amount of flux which crosses the equator determines the amount of net flux in each hemisphere, it follows that the cross-equatorial plumes introduce an uncertainty in the prediction of the net flux in each hemisphere. This leads to an uncertainty in predictions of the strength of the following cycle.
119516456
tan{beta} determination from heavy Higgs boson production at linear colliders
We study the production at future e{sup +}e{sup -} linear colliders of the heavy neutral Higgs bosons H and A of the minimal supersymmetric standard model in association with top and bottom quarks. The cross sections have a strong dependence on the parameter tan{beta}, and thus provide a good way to determine it. At a linear collider with s=0.5--1 TeV and expected integrated luminosities, we find significant sensitivities for determining tan{beta}. In the supergravity scenario, the sensitivity is particularly strong for tan{beta}{approx}>10, reaching a 15% or better measurement. In the general MSSM scenario, the interplay between the 4b and 4t channels results in a good determination for tan{beta}{approx}<10, while the sensitivity is weakened for higher values of tan{beta}.
208866861
F-SU(5)
We construct three flipped SU(5) x U(1)x models from F-theory, and consider two such models from free fermionic string model building. To achieve the decoupling scenario in F-theory models and the string-scale gauge coupling unification in free fermionic models, we introduce vector-like particles at the TeV scale that can be observed at the Large Hadron Collider. We study gauge coupling unification, and find that proton decay is within the reach of the future Hyper-Kamiokande experiment. In these models, the doublet-triplet splitting problem and monopole problem can be solved, the neutrino masses and mixings can be explained via the double seesaw or seesaw mechanism, the observed baryon asymmetry can be obtained through leptogenesis, the hybrid inflation can be realized, and the correct cosmic primordial density fluctuations can be generated. (C) 2009 Elsevier B.V. All rights reserved.
45695550
Evidence for length-dependent wire expansion, filament dedensification and consequent degradation of critical current density in Ag-alloy sheathed Bi-2212 wires
It is well known that longer Bi-2212 conductors have significantly lower critical current density (Jc) than shorter ones, and recently it has become clear that a major cause of this reduction is internal gas pressure generated during heat treatment, which expands the wire diameter and dedensifies the Bi-2212 filaments. Here we report on the length-dependent expansion of 5–240 cm lengths of state-of-the-art, commercial Ag alloy sheathed Bi-2212 wire after full and some partial heat treatments. Detailed image analysis along the wire length shows that the wire diameter increases with distance from the ends, longer samples often showing evident damage and leaks provoked by the internal gas pressure. Comparison of heat treatments carried out just below the melting point and with the usual melt process makes it clear that melting is crucial to developing high internal pressure. The decay of Jc away from the ends is directly correlated to the local wire diameter increase, which decreases the local Bi-2212 filament mass density and lowers Jc, often by well over 50%. It is clear that control of the internal gas pressure is crucial to attaining the full Jc of these very promising round wires and that the very variable properties of Bi-2212 wires are due to the fact that this internal gas pressure has so far not been well controlled.
139229583
Tests of HTS insert coils above 30 T
Recently HTS insert coils have been operated in background magnetic fields over 30 T, reaching record values for the central magnetic field. One YBCO double pancake coil generated 2.8 T in a 31 T background for a total of 33.8 T. A Bi-2212 layer wound coil generated 1.1 T in a 31 T background for a total of 32.1 T. Here we report on the test set-up and the obtained results. Introduction •Goal: demonstrate the suitability of HTS conductors > 30 T •Two insert coils are built and tested in a background magnetic field of 31 T. 1) YBCO insert coil with commercial conductor from SuperPower Inc. 2) Bi-2212 coil using commercial φ 1 mm wire from Oxford Instruments, Superconducting Technology (OST). •Coils are wound and tested at the NHMFL in a 31 T resistive magnet with a 39 mm diameter cryostat. •HTS coils were protected with a quench detection system, circuit breakers and a 0.5 Ohm dump resistor units YBCO coil Bi-2212 coil Conductor 4 by 0.1 mm tape φ 1 mm wire Insulation varnish ceramic braid Impregnation none Epoxy VPI Conductor length m 36 66 Self-inductance mH 1.9 2.6 Field constant mT/A 8.7 9.1 Typical Ic A 120 A at 77 K, SF 330 A at 4.2 K, 5T
118289508
A transformative superconducting magnet technology for fields well above 30 T using isotropic round wire multifilament Bi2Sr2CaCu2O8-x conductor
We report here that magnetic fields of almost 34 T, far above the upper 24 T limit of Nb3Sn, can be generated using a multifilament round wire conductor made of the high temperature cuprate superconductor Bi2Sr2CaCu2O8-x (Bi-2212). A remarkable attribute of this Bi-2212 conductor is that it does not exhibit macroscopic texture and contains many high angle grain boundaries but nevertheless attains very high superconducting critical current densities Jc of 2500 A/mm2 at 20 T and 4.2 K. This Bi-2212 conductor does not possess the extreme texture that high Jc coated conductors of REBa2Cu3O7-x (REBCO) require, avoiding also its high aspect ratio, large superconducting anisotropy and the inherent sensitivity to defects of a single filament conductor. Bi-2212 wires can be wound or cabled into almost any type of superconducting magnet and will be especially valuable for very high field NMR magnets beyond the present 1 GHz proton resonance limit of Nb3Sn technology. This demonstration that grain boundary limits to high Jc can be practically overcome suggests the huge value of a renewed focus on grain boundary properties in non-ideal geometries, especially with the goal of translating the lessons of this Bi-2212 conductor into fabrication of multifilament round wire REBCO or Fe-based superconductors.
205409621
Isotropic round-wire multifilament cuprate superconductor for generation of magnetic fields above 30 T.
Magnets are the principal market for superconductors, but making attractive conductors out of the high-temperature cuprate superconductors (HTSs) has proved difficult because of the presence of high-angle grain boundaries that are generally believed to lower the critical current density, J(c). To minimize such grain boundary obstacles, HTS conductors such as REBa2Cu3O(7-x) and (Bi, Pb)2Sr2Ca2Cu3O(10-x) are both made as tapes with a high aspect ratio and a large superconducting anisotropy. Here we report that Bi2Sr2CaCu2O(8-x) (Bi-2212) can be made in the much more desirable isotropic, round-wire, multifilament form that can be wound or cabled into arbitrary geometries and will be especially valuable for high-field NMR magnets beyond the present 1 GHz proton resonance limit of Nb3Sn technology. An appealing attribute of this Bi-2212 conductor is that, being without macroscopic texture, it contains many high-angle grain boundaries but nevertheless attains a very high J(c) of 2,500 A mm(-2) at 20 T and 4.2 K. The large potential of the conductor has been demonstrated by building a small coil that generated almost 2.6 T in a 31 T background field. This demonstration that grain boundary limits to high Jc can be practically overcome underlines the value of a renewed focus on grain boundary properties in non-ideal geometries.