Runaway Type Research Articles

Probing multimode applicator of microwave heating system for E‐field distribution using a silicon carbide sensor and a shielded thermocouple

AbstractMeasurement of the field distribution in a multimode applicator of a microwave heating system has been a challenging problem. We report here a simple but comprehensive scheme for its semi‐quantitative estimation under no‐load conditions. It involves the measurement of temperature (T) versus time (t) profiles in a small silicon carbide (SiC) sensor ring positioned at the junction end of a metal‐jacketed microwave‐compatible thermocouple probe arrangement. These heating profiles (T vs. t) were measured using a data acquisition system, keeping the SiC ring at different (x, y, z) positions in the applicator. Using this measurement scheme, the spatial positions with local field minimum as inferred from very high reflected power or those with local field maximum with associated thermal runaway type condition could be well identified. Given the thermal and the dielectric properties of SiC material and the physical dimensions of the sensor ring, a uniform microwave field‐based model with a thermal lumped element type approximation (with no thermal gradient across SiC) was applied for analysis of the T versus t heating profiles. Within this model, the locally effective electric field E could be inferred for low and moderate electric field ranges. While the accuracy of the field estimation is currently limited by the use of the metal‐jacketed thermocouple and other factors, this SiC sensor‐based methodology has the potential to be developed further to be useful in the area of microwave applicator design.

Stability and vacuum energy in open string models with broken supersymmetry

We construct type I string models with supersymmetry broken by compactifi- cation that are non-tachyonic and have exponentially small effective potential at one-loop. All open string moduli can be stabilized, while the closed string moduli remain massless at one-loop. The backgrounds of interest have rigid Wilson lines by the use of stacked branes, and some models should have heterotic duals. We also present non-tachyonic backgrounds with positive potentials of runaway type at one-loop. This class of models could be used to test various swampland conjectures.

Tachyon field non-minimally coupled to massive neutrino matter

In this paper, we consider rolling tachyon, with steep run-away type of potentials non-minimally coupled to massive neutrino matter. The coupling dynamically builds up at late times as neutrino matter turns non-relativistic. In case of scaling and string inspired potentials, we have shown that non-minimal coupling leads to minimum in the field potential. Given a suitable choice of model parameters, it is shown to give rise to late-time acceleration with the desired equation of state.

Pre-failure instability of sand under dilatancy rate controlled conditions

Experimental results are presented in this paper to show that a runaway type of pre-failure instability can occur for sand under dilatancy rate controlled conditions when an appropriate strain increment ratio, dεv/dε1, is imposed. This type of instability is similar to the runaway type of instability observed for very loose sand under undrained conditions. Whether a soil element will undergo pre-failure instability depends on the difference between the strain increment ratio of the soil obtained from drained test, under a specified effective confining pressure, (dεv/dε1)s, and the strain increment ratio imposed during the test, (dεv/dε1)i, rather than the absolute magnitude of (dεv/dε1)i. Based on the experimental data obtained in this study it was found that an instability line can be determined from a series of strain path tests conducted at different effective confining pressures but with the same dεv/dε1 by joining the peak points of the effective stress paths to the origin in the q–p′ stress space. This line is similar to the instability line obtained from undrained tests on loose sand. The instability tests under dilatancy rate controlled conditions indicate that the stress ratio at the onset of instability obtained in the instability tests coincide with the peak stress ratio line. This suggests that the peak stress line can be used to predict the onset of instability under dilatancy rate controlled conditions in the same way as the use of instability line to predict the onset of instability under undrained conditions.

Higgs pair production at the LHC and ILC from a general potential

Higgs cubic coupling plays a crucial role in probing an origin of electroweak symmetry breaking. It is expected that the cubic coupling is measured by Higgs pair production at the LHC and ILC, and the deviations from the standard model can be extracted from the Higgs pair production process, and those can give us a hint of new physics beyond the standard model. We consider a general potential that achieves the suitable electroweak symmetry breaking. As one of the interesting models, we suggest a nonperturbative Higgs model in which a runaway type of potential is used. In the model, the cross sections of pair production at the LHC are enlarged compared to the standard model. We also study the Higgs pair production induced by a noncanonical kinetic term of Higgs fields which will be important for searching the pair production at the ILC.

Diffuse instabilities with transition to localization in loose granular materials

SUMMARYThis paper is concerned with diffuse and other ensuing failure modes in geomaterials when tested under homogeneous states of shearing in various loading programs and drainage conditions. Material instability is indeed the basic property that accounts for the instability of an initially homogeneous deformation field leading to diffuse failure and strain localization in geomaterials. The former is normally characterized by a runaway type of failure accompanied with a sudden and violent collapse of the material in the absence of any localization phenomena. Against this backdrop, we present a brief overview of material instability in elastoplastic solids where one finds a rich source of theoretical concepts including bifurcation, strain localization, diffuse failure and second‐order work, as well as a considerable body of experiments. Some compelling laboratory experimental studies of material instability with focus to diffuse failure are then presented and interpreted based on the second‐order work. Finally, various material instability analyses using an elastoplastic constitutive and a general finite element analysis of the above‐mentioned laboratory experimental tests are presented as a boundary value problem. It is shown that instability can be captured from otherwise uniform stress, density and hydraulic states, whereas uniform deviatoric loads are being applied on the external boundaries of a specimen. Although the numerical simulations reproduce well the laboratory experimental results, they also highlight the hierarchy of failure modes where localization phenomena emerge in the post‐bifurcation regime as a result of a degradation of homogeneity starting from a diffuse mode signalled by a zero second‐order work. Copyright © 2012 John Wiley & Sons, Ltd.

Factors affecting pre-failure instability of sand under plane-strain conditions

Experimental data obtained from a plane-strain apparatus are presented in this paper to show that a pre-failure instability in the form of a rapid and sustained increase in strain rate can occur for both contractive and dilative sand under fully drained conditions. However, this type of instability is different from the runaway type of instability observed under undrained conditions, and has therefore been called conditional instability. Despite the differences, the conditions for both types of instability are the same for contractive sand. There are also other factors that affect the pre-failure instability of sand observed in the laboratory. These include the stress ratio, void ratio, sand state, load control mode and reduction rate of the effective confining stress. In this paper, these factors are discussed and analysed using experimental data obtained from undrained instability (or creep) tests and constant shear drained (CSD) tests carried out under plane-strain conditions.

Conformality or confinement (II): one-flavor CFTs and mixed-representation QCD

We study QCD-like four dimensional theories in the theoretically controlled framework of deformation theory and/or twisted partition function on S*1 x R*3. By using duality, we show that a class of one-flavor theories exhibit new physical phenomena: discrete chiral symmetry breaking induced by the condensation of topological disorder operators, and confinement and the generation of mass gap due to new non-selfdual topological excitations. In the R*4 limit, we argue that the mass gap disappears, the chiral symmetry breaking vacua are of runaway type, and the theory flows to a CFT. We also study mixed-representation theories and find abelian chiral symmetry breaking by topological operators charged under abelian chiral symmetries. These are reminiscent to, but distinct, from Seiberg-Witten theory with matter, where 4d monopoles have non-abelian chiral charge. This examination also helps us refine our recent bounds on the conformal window. In an Addendum, we also discuss mixed vectorlike/chiral representation theories, obtain bounds on their conformal windows, and compare with the all-order beta function results of arXiv:0911.0931.

Parametrization of quintessence and its potential

We develop a theoretical method of constructing the quintessence potential directly from the effective equation of state function $w(z)$, which describes the properties of the dark energy. We apply our method to four parametrizations of equation of state parameter and discuss the general features of the resulting potentials. In particular, it is shown that the constructed quintessence potentials are all in the form of a runaway type.

Vacuum structure of spontaneously brokenN=2supersymmetric gauge theory

We analyze the vacuum structure of spontaneously broken $\mathcal{N}=2$ supersymmetric gauge theory with the Fayet-Iliopoulos term. Our theory is based on the gauge group $\mathrm{SU}(2)\ifmmode\times\else\texttimes\fi{}\mathrm{U}(1)$ with ${N}_{f}=1,2$ massless quark hypermultiplets having the same $\mathrm{U}(1)$ charges. In the classical potential, there are degenerate vacua even in the absence of supersymmetry. It is shown that this vacuum degeneracy is smoothed out, once quantum corrections are taken into account. In the ${N}_{f}=1$ case, the effective potential is found to be the so-called runaway type, and there is neither a well-defined vacuum nor a local minimum. On the other hand, in the ${N}_{f}=2$ case, while there is also the runaway direction in the effective potential, we find the possibility that there appears a local minimum with broken supersymmetry at the degenerate dyon point.

A new runaway type episomal vector for mammalian cells based on a temperature-sensitive simian virus 40 and inducible erythropoietin production.

A runaway vector for mammalian cells was constructed from the simian virus 40 (SV40) genome with a temperature-sensitive mutation of the large T antigen and bacterial neor gene. Replication of this plasmid was repressed above 39 degrees C and vigorous DNA propagation was observed below 33 degrees C in simian CV-1 cells. The human erythropoietin gene was inserted downstream of the SV40 late promoter of the plasmid and the recombinant plasmid was introduced into CV-1 cells. By a temperature shift from 37 to 33 degrees C, the plasmid copy number increased from 5 x 10(2) to 5 x 10(3) copies per cell and the specific production rate of erythropoietin increased more than ten-fold. The bacterial-derived sequences such as the neor gene and vector pUC sequences were prone to delete but the main body of the recombinant plasmid such as SV40 and the erythropoietin-coding sequences were stably maintained at either 33 or 37 degrees C.