Presence Of Flux Research Articles

Heating up branes in gauged supergravity

In this note, we explore the solution space of non-extremal black objects in $4D$ and $5D$ ${\cal N}=2$ gauged supergravity in the presence of fluxes. We present first order rewritings of the $4D$ action for a classes of non-extremal dyonic and electric solutions with electric flux backgrounds. Additionally, we obtain the non-extremal version of the Nernst brane in $AdS_5$ using a simple deformation. Finally, we develop a new technique to deform extremal black solutions in $4D$ to non-extremal solutions by an analysis of the symmetries of the equations of motion.

Wetting of Cu Pads by Bi-2.6Ag-xCu Alloys and Phase Equilibria in the Ag-Bi-Cu System

The phase equilibrium in the Ag-Bi-Cu system was experimentally determined at 573 K, 773 K, and 973 K by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) on annealed alloys and liquid/solid couples. The experimental results indicate that the mutual solubility of the components is limited. Based on the present results and literature data, phase equilibria in the Ag-Bi-Cu system were thermodynamically assessed. Wetting of Bi-2.6Ag-xCu alloys on Cu substrates was studied with the sessile drop method in the presence of flux at 573 K and 623 K. It was found that the wetting to non-wetting transition corresponds to the solubility limit of Cu in liquid. Selected solidified solder–substrate couples were cross-sectioned and their interfacial microstructure examined with SEM–EDS. There are no reaction products at the interface, but the copper surface becomes rough because of dissolution by liquid solder.

Effects of fluxes on the structure and filtration properties of diatomite filter aids

Diatomite filter aids were prepared using raw diatomite and various fluxes. The effects of composition, amount and granularity of the flux on the micro-structure and filtration performance of the diatomite filter aids were studied. Filter aids with high flow rate and filtrate clarity were successfully obtained when 7wt. % of Na2CO3 flux was employed. It was shown that opal in the diatomite was converted to cristobalite in the presence of flux at 1000°C, being similar to the formative process of silicate glass. The additive alkali ions from the flux are believed to partially break SiOSi chains of the opal at a high temperature and then recombine the broken structure to a hexatomic ring mesh structure during the cooling process, which is significative to control the phase composition for preparation of diatomite filter aids.

Mirage models confront the LHC. II. Flux-stabilized type IIB string theory

We continue the study of a class of string-motivated effective supergravity theories in light of current data from the CERN Large Hadron Collider (LHC). In this installment we consider type IIB string theory compactified on a Calabi-Yau orientifold in the presence of fluxes, in the manner originally formulated by Kachru et al. We allow for a variety of potential uplift mechanisms and embeddings of the Standard Model field content into $D3$-and $D7$-brane configurations. We find that an uplift sector independent of the K\"ahler moduli, as is the case with anti-$D3$-branes, is inconsistent with data unless the matter and Higgs sectors are localized on $D7$ branes exclusively, or are confined to twisted sectors between $D3$-and $D7$-branes. We identify regions of parameter space for all possible $D$-brane configurations that remain consistent with Planck observations on the dark matter relic density and measurements of the $CP$-even Higgs mass at the LHC. Constraints arising from LHC searches at $\sqrt{s}=8\text{ }\text{ }\mathrm{TeV}$ and the LUX dark matter detection experiment are discussed. The discovery prospects for the remaining parameter space at dark matter direct-detection experiments are described, and signatures for detection of superpartners at the LHC with $\sqrt{s}=14\text{ }\text{ }\mathrm{TeV}$ are analyzed.

T-duality in gauged linear sigma-models with torsion

Abstract (0,2) gauged linear sigma models with torsion, corresponding to principal torus bundles over warped CY bases, provide a useful framework for getting exact statements about perturbative dualities in the presence of fluxes. In this context we first study dualities mapping the torus fiber onto itself, implying the existence of quantization constraints on the torus moduli for consistency. Second, we investigate dualities mixing the principal torus bundle with the gauge bundle, relating the torsional GLSMs to ordinary ones corresponding to CY compactifications with non-standard embeddings, namely two classes of models with different target-space topologies.

Molten salt synthesis, characterization, and luminescence properties of GdNbO4/LuTaO4:Eu3+ phosphors

GdNbO4:Eu3+ and LuTaO4:Eu3+ have been successfully prepared with different fluxes (NaCl, KCl, NaCl and KCl) by the molten salt method. X-ray diffraction (XRD) patterns illustrated that well crystallized GdNbO4:Eu3+ and LuTaO4:Eu3+ in the presence of fluxes were formed under reduced temperature (900°C) in contrast to conventional method (GdNbO4:Eu3+: around 1200°C; LuTaO4:Eu3+: around 1500°C). Scanning electron microscope (SEM) images revealed that well dispersed particles were achieved (granular or rod-like structures). Meanwhile, the photo-luminescent studies demonstrated that both niobate and tantalate are efficient hosts to sensitize europium red emissions. The results indicated that GdNbO4:Eu3+ using NaCl as the flux gave much enhanced red emission whereas LuTaO4:Eu3+ synthesized with the assistance of mixed salts (NaCl–KCl) achieved the best luminescence.

Z p charged branes in flux compactifications

We consider 4d string compactifications in the presence of fluxes, and classify particles, strings and domain walls arising from wrapped branes which have charges conserved modulo an integer p, and whose annihilation is catalized by fluxes, through the Freed-Witten anomaly or its dual versions. The Z p -valued strings and particles are associated to Z p discrete gauge symmetries, which we show are realized as discrete subgroups of 4d U(1) symmetries broken by their Chern-Simons couplings to the background fluxes. We also describe examples where the discrete gauge symmetry group is actually non-Abelian. The Z p -valued domain walls separate vacua which have different flux quanta, yet are actually equivalent by an integer shift of axion fields (or further string duality symmetries). We argue that certain examples are related by T-duality to the realization of discrete gauge symmetries and Z p charges from torsion (co)homology. At a formal level, the groups classifying these discrete charges should correspond to a generalization of K-theory in the presence of general fluxes (and including fundamental strings and NS5-branes).

Compactified rotating branes in the matrix model, and excitation spectrum towards one loop

We study compactified brane solutions of type R^4 x K in the IIB matrix model, and obtain explicitly the bosonic and fermionic fluctuation spectrum required to compute the one-loop effective action. We verify that the one-loop contributions are UV finite for R^4 x T^2, and supersymmetric for R^3 x S^1. The higher Kaluza-Klein modes are shown to have a gap in the presence of flux on T^2, and potential problems concerning stability are discussed.

Addition of sedimentary rock to kaolinitic clays: influence on sintering process

The physical and mechanical properties of clay-based ceramic probes with sedimentary rock added as the non-plastic component were evaluated. Samples were prepared with 0, 20, 40, 60 and 80 wt.% of rock added to the clay material. Pressed (7 ton) probes were sintered at 500, 800, 900, 1000, 1100 and 1200 °C and submitted to X-ray diffraction analysis and technological characterization. The X-ray diffraction results showed that the sedimentary rock had micaceous clay minerals, while the clay material had kaolinite as the main phases. Thermal analysis and X-ray diffraction showed reactions that indicated transformation (inversion of quartz), decomposition (loss of hydroxides) and phase formation (mullite) during heat treatment of the samples. The technological tests showed that the addition of sedimentary rock improved some properties of the sintered material, aided by the presence of fluxes. However, the presence of quartz in the rock hampered the formation of the mullite phase. The formation of new phases and transformations occurring during the heating and cooling of the samples helped explain the technological properties of ceramic materials.

Understanding how brass ball valves passing certification testing can cause elevated lead in water when installed

The lead leaching potential of new brass plumbing devices has come under scrutiny as a significant source of lead in drinking water (>300 μg/L) of new buildings around the world. Experiments were conducted using ball valves that were sold as certified and known to have caused problems in practice, in order to better understand how installed products could create such problems, even if they passed “leaching tests” such as National Sanitation Foundation (NSF) Standard 61 Section 8. Diffusion of lead from within the device into water when installed can increase lead leaching by orders of magnitude relative to results of NSF testing, which once only required exposure of very small volumes of water within the device. “Normalization” of the lead-in-water result tended to produce estimates of lead concentration that were much lower than actual lead measured at the tap. Finally, the presence of flux could also dramatically increase lead leaching, whereas high water velocity had relatively little effect.

Investigation of the wetting of PCBs with SnCu (HASL) and Snimm finishes by SnZnBiIn solders

PurposeThe purpose of this article is to establish why the wetting on PCBs with SnCu (HASL) and Snimm finishes in the presence of a flux is better than the wetting of those on a copper substrate. The practical aspect of the obtained results is the main goal of these investigations.Design/methodology/approachThe authors applied the wetting balance method for the wetting measurements at 230 and 250°C, in nitrogen atmosphere, in the presence of the ORM0 type flux. The PCBs with the SnCu (HASL) and Snimm finishes were investigated in the state “as received”. To establish the wetting properties of the SnCu (HASL) and Snimm finishes on the PCBs, wetted by the investigated SnZnBiIn alloys, the SEM and EDX analyses were performed.FindingsThe authors obtained very good wetting results of the PCBs with the SnCu and Snimm finishes, wetted by the SnZn7Bi3In4 alloys. By applying the SEM and EDX methods, it was possible to establish that the barrier layer which was created during the HASL process between the copper and the SnCu solder is efficient enough to protect the copper against the influence of the Zn atoms from the SnZn7Bi3In4 solder. This is the reason for an improvement of the wetting properties. An immersion tin finish does not create such barrier layer with the copper. It results in a worse wetting than for the SnCu finishes but a better one than that for the copper. Immersion tin dissolves in the alloys during the soldering and this process delays the reaction between the copper and the Zn atoms from the SnZn7Bi3In4 solder.Research limitations/implicationsIt is suggested that further studies are necessary for the confirmation of the practical application, but they should be limited to the reliability of the solder joint performance.Practical implicationsThe best wetting results of the PCBs with “tin finishes”, especially with SnCu, wetted by the SnZn7Bi3In4 alloy, at 230 and 250°C and in nitrogen atmosphere, suggest a possibility of a practical usage of the tin‐zinc‐bismuth‐indium alloys for soldering in electronics.Originality/valueThe wetting balance method combined with the SEM and EDX analyses were used as the quickest way to determine the mechanism of the better wettability properties in the case of the PCBs with the SnCu and Snimm finishes, wetted by the SnZn7Bi3In4 alloy, compared to those of the PCBs on the Cu substrate.

Thermal Properties and Wetting Behavior of High Temperature Zn-Al-In Solders

Solders for ultrahigh-temperature applications were defined by Vianco as those able to sustain working conditions with temperatures as high as 573 K, with momentary temperature rise up to 623 K. Zn-Al eutectic alloy (12 at.% Al) fits such defined criteria with respect to its melting temperature. It was found that small additions of indium to Zn-Al eutectic lower its melting temperature. The aim of this work is to assess if and to what extent thermal properties and wetting behavior are affected. It was found that addition of In increases electrical resistivity and coefficient of thermal expansion value. Wetting angles on Cu and Al substrates of liquid Zn-Al eutectic-based alloys containing up to 1.5 at.% of In were studied with the sessile drop method, after wetting at 773 K in the presence of flux. A decrease of apparent wetting angle was observed with increasing concentration of In. After wetting tests solidified alloy-substrate couples were cross-sectioned and examined with scanning electron microscopy coupled with electron dispersive X-ray analysis.

Transport properties of mesoscopic graphene rings

Based on a recursive Green's function method, we investigate the conductance of mesoscopic graphene rings in the presence of disorder, in the limit of phase coherent transport. Two models of disorder are considered: edge disorder and surface disorder. Our simulations show that the conductance decreases exponentially with the edge disorder and the surface disorder. In the presence of flux, a clear Aharonov–Bohm conductance oscillation with the period Φ 0 ( Φ 0= h/ e) is observed. The edge disorder and the surface disorder have no effect on the period of AB oscillation. The amplitudes of AB oscillations vary with gate voltage and flux, which is consistent with the previous results. Additionally, ballistic rectification and negative differential resistance are observed in I– V curves, with on/off characteristic.

Open M2-branes with flux and the modified Basu–Harvey equation

The supersymmetric actions of closed multiple M2 branes with flux for the Bagger–Lambert (BL) and ABJM theories have been constructed recently by Lambert and Richmond (2009 J. High Energy Phys. JHEP10(2009)084). In this paper, we extend the construction to the case of open M2-branes with flux and derive the boundary conditions. This allows us to derive the modified Basu–Harvey equation in the presence of flux. As an example, we consider the Lorentzian BL model. A new feature of the fuzzy funnel solution describing a D2–D4 intersection is obtained as a result of the flux.

Quasiparticle Relaxation of Superconducting Qubits in the Presence of Flux

Quasiparticle tunneling across a Josephson junction sets a limit for the lifetime of a superconducting qubit state. We develop a general theory of the corresponding decay rate in a qubit controlled by a magnetic flux. The flux affects quasiparticles tunneling amplitudes, thus making the decay rate flux-dependent. The theory is applicable for an arbitrary quasiparticle distribution. It provides estimates for the rates in practically important quantum circuits and also offers a new way of measuring the phase-dependent admittance of a Josephson junction.

Investigation of the effect of indium addition on wettability of Sn‐Ag‐Cu solders

PurposeThe purpose of this paper is to investigate the influence of In additions on the wetting properties of the Sn2.86Ag0.40Cu (in wt%) eutectic‐based alloys, on a copper substrate, in the presence of a flux. The main goal was to find correlations between the results of the wetting balance (WB) and the sessile drop (SD) method, in relation to the contact angles.Design/methodology/approachThe WB method was applied for the wetting measurements, at 250°C, in an air atmosphere and in the presence of a flux. The SD measurements were conducted at the same temperature, in the presence of the same flux, but in an Ar atmosphere, while the maximum bubble pressure (MBP) and dilatometric measurements were conducted in an Ar+H2 atmosphere. The density data from the dilatometric method were used for the determination of the surface tension by means of MBP, and the WB method was used to determine the surface and interfacial tension. Next, the surface tension data from these two methods were compared. The WB data were used to calculate the contact angles and the obtained indirect data were compared with the results of the direct SD measurements of the contact angle.FindingsA higher In content in the alloy resulted in a lower contact angle on the copper, and the WB results agreed well with the results of the SD experiments. It was confirmed that, in liquid In‐Sn and the alloys containing In and Sn (Ag‐In‐Sn, Sn‐Ag‐Cu‐In, Sn‐Zn‐In), the improvement of the wettability was indicated only by the increase of the contact angle with the increasing In content.Research limitations/implicationsFurther studies are necessary for the confirmation of practical application, but they should be directed to the soldering of high indium alloys on printed circuit boards, with different finishes and qualities of the solder joint performance.Practical implicationsTaking into account the contact angle data from the WB and SD methods, the best results of the SAC‐In alloy on copper were obtained for the alloy of the highest In content. It was found that the contact angles from SD after 4 s were higher (non‐equilibrium conditions) than the values calculated from WB after 3 s. In contrast, the contact angles from SD after 10 min (equilibrium conditions) were lower than those from WB after 3 s. The comparison suggests that the contact angles from WB are situated within the data from SD, showing the same lowering tendency with the increasing content of In, and they may be well accepted for practical purposes. On the other hand, the sample of the solder in the SD method, after a prolonged time – in order to get the equilibrium contact angle – may be used to study the interfacial phenomena with the Cu substrate. The differential thermal analysis results indicate that the melting temperature decreases with increasing tin concentration. Taking into account the results of this study and the available literature data, alloys containing 8‐10 wt% of In can be recommended for practical application.Originality/valueThe WB and SD methods were used for the contact angle determination of a wide range of solder compositions, in the same temperature and flux conditions. Also, the surface tensions for these alloys were determined with the use of two independent methods: the MBP and the WB methods. The results obtained made it possible to draw conclusions regarding the correlation between the output of different methods and the conditions in which a comparison of the results can be made. It is supposed that these observations apply to many other alloy systems.

Hidden symmetry in the presence of fluxes

We derive the most general first-order symmetry operator for the Dirac equation coupled to arbitrary fluxes. Such an operator is given in terms of an inhomogeneous form ω which is a solution to a coupled system of first-order partial differential equations which we call the generalized conformal Killing–Yano system. Except trivial fluxes, solutions of this system are subject to additional constraints. We discuss various special cases of physical interest. In particular, we demonstrate that in the case of a Dirac operator coupled to the skew symmetric torsion and U ( 1 ) field, the system of generalized conformal Killing–Yano equations decouples into the homogeneous conformal Killing–Yano equations with torsion introduced in D. Kubiznak et al. (2009) [8] and the symmetry operator is essentially the one derived in T. Houri et al. (2010) [9]. We also discuss the Dirac field coupled to a scalar potential and in the presence of 5-form and 7-form fluxes.

Investigation of Sn‐Zn‐Bi solders – Part II: wetting measurements on Sn‐Zn7Bi solders on copper and on PCBs with lead‐free finishes by means of the wetting balance method

PurposeThe purpose of this paper is to investigate the influence of Bi additions on the wetting properties of SnZn7Bi alloys (Bi=1 and 3 per cent by mass) on a copper substrate and printed circuit boards (PCBs) with lead‐free finishes (SnCu, immersion Sn, Ni/Au, organic solderability preservative) in the presence of fluxes. The practical implications of the results is the main purpose of these investigations.Design/methodology/approachA wetting balance method was used for wetting measurements at 230 and 250°C in nitrogen and air atmospheres in the presence of ORM0‐ or ROL0‐type fluxes. The PCBs were investigated ‘as received’ and after accelerated aging. The analysis of variance (ANOVA) analysis was performed in order to explain how the main factors of the experiments (the Bi content in the alloy (1 or 3 per cent), the test temperature and the test atmosphere) influenced the wetting ability of SnZn7Bi on Cu substrates.FindingsAs expected, a higher temperature and a higher Bi content in the alloy favoured the wetting of the copper substrate in the presence of the ORM0‐type flux in a nitrogen atmosphere. These results were confirmed by ANOVA analysis. Very good results were also obtained for the SnZn7Bi3 alloy's wettability on “tin coatings” on PCBs (SnCu and immersion Sn) both “as received” and after aging, in the presence of the ORM0‐type flux, for all the applied testing conditions (in both temperatures and N2 and air atmospheres). The less active flux (ROL0) caused a worsening of the alloy's wettability properties; however, the PCBs with SnCu and immersion Sn finishes maintained their wettability, even after aging, at very good and good levels, respectively.Research limitations/implicationsIt is suggested that further studies are necessary for confirmation of the practical application, but they should be limited to the soldering of SnZnBi3 on PCBs with “tin coatings” and the quality of the solder joint performance.Practical implicationsThe best SnZn7Bi3 wetting results on PCBs with “tin coatings” (SnCu and immersion Sn) at 230 and 250°C and in N2 and air atmospheres suggest the possibility of a practical usage of the tin‐zinc‐bismuth alloys for soldering in electronics using both the ORM0‐type flux and the even less active ROL0‐type flux, which are currently used in industrial lead‐free soldering processes.Originality/valueThe wetting balance method, combined with ANOVA was used as the quickest way to determine the wettability properties of SnZn7Bi on Cu substrates. Wettability measurements were also performed on the SnZn7 and SnZn7Bi alloys with different lead‐free finishes, in different experimental conditions.

COMPACTIFICATION OF TYPE IIB THEORY WITH FLUXES AND AXION–DILATON STRING COSMOLOGY

Compactification of type IIB theory on torus, in the presence of fluxes, is considered. The reduced effective action is expressed in manifestly S-duality invariant form. Cosmological solutions of the model are discussed in several cases in the Pre-Big Bang scenario.

Remarks on [formula omitted] and [formula omitted] with each carrying a flux

We explore various properties of interaction between Dp and Dp′ with each carrying a world-volume flux and with the p′-branes placed along p′ spatial world-volume directions of the p-branes at a separation when p−p′=2. Carefully analyzing the annulus amplitudes calculated via the boundary state approach, we find that many features of amplitudes remain similar to those studied when p=p′ such as the nature of force on the brane separation, the onset of various instabilities when the brane-separation is on the order of string scale and the occurrence of pair production of open strings when there is a relevant electric flux present. In addition, we have also found many new features of interaction which don't appear in the absence of fluxes or when p=p′ in the presence of fluxes, for example, the nature of interaction can be repulsive and there is no onset of tachyonic instability under certain conditions. Even in the absence of a magnetic flux, we can have an exponential enhancement of the rate of pair production of open strings in certain cases, which may be significant enough to give observational consequences.