Auxiliary Field Research Articles

What Is the Fate of Hawking Evaporation in Gravity Theories with Higher Curvature Terms?

During the final stages of black hole evaporation, ultraviolet deviations from general relativity eventually become dramatic, potentially affecting the end state. We explore this problem by performing nonlinear simulations of wave packets in Einstein-dilaton-Gauss-Bonnet gravity, the only gravity theory with quadratic curvature terms which can be studied at a fully nonperturbative level. Black holes in this theory have a minimum mass but also a nonvanishing temperature. This poses a puzzle concerning the final fate of Hawking evaporation in the presence of high-curvature nonperturbative effects. By simulating the mass loss induced by evaporation at the classical level using an auxiliary phantom field, we study the nonlinear evolution of black holes past the minimum mass. We observe a runaway shrink of the horizon (a nonperturbative effect forbidden in general relativity) which eventually unveils a high-curvature elliptic region. While this might hint to the formation of a naked singularity (and hence to a violation of the weak cosmic censorship) or of a pathological spacetime region, a different numerical formulation of the initial-value problem in this theory might be required to rule out other possibilities, including the transition from the critical black hole to a stable horizonless remnant. Our Letter is relevant in the context of the information-loss paradox, dark-matter remnants, and for constraints on microscopic primordial black holes.

Travelling chimeras in oscillator lattices with advective-diffusive coupling.

We consider a one-dimensional array of phase oscillators coupled via an auxiliary complex field. While in the seminal chimera studies by Kumamoto and Battogtokh only diffusion of the field was considered, we include advection which makes the coupling left-right asymmetric. Chimera starts to move and we demonstrate that a weakly turbulent moving pattern appears. It possesses a relatively large synchronous domain where the phases are nearly equal, and a more disordered domain where the local driving field is small. For a dense system with a large number of oscillators, there are strong local correlations in the disordered domain, which at most places looks like a smooth phase profile. We find also exact regular travelling wave chimera-like solutions of different complexity, but only some of them are stable. This article is part of the theme issue 'New trends in pattern formation and nonlinear dynamics of extended systems'.

Link auxiliary field method in the extended Hubbard model.

The aim of this work is to generalize the method of Hubbard fields in fermion quantum Monte Carlo simulations to the case of link fields. The introduced Hubbard link fields play the role of the interaction fields responsible for the attraction and repulsion of electronic excitations at the nodes. Such improvements lead to a number of advantages concerning thermalization time, autocorrelations, metastable states, and probability distributions of the quantities. It is demonstrated that computations using five fields are more stable and reliable in the case of energy observables.

Bulk gauge fields and holographic RG from exact RG

Recently, a method was described for deriving Holographic RG equation in AdSD+1 space starting from an Exact RG equation of a D-dimensional boundary CFT [22]. The evolution operator corresponding to the Exact RG equation was rewritten as a functional integral of a D + 1 dimensional field theory in AdSD+1 space. This method has since been applied to elementary scalars and composite scalars in the O(N) model [34]. In this paper, we apply this technique to the conserved vector current and the energy momentum tensor of a boundary CFT, the O(N) model at a fixed point. These composite spin one and spin two operators are represented by auxiliary fields and extend into the bulk as gauge fields and metric perturbations. We obtain, at the free level, the (gauge fixed) Maxwell and Einstein actions. While the steps involved are motivated by the AdS/CFT correspondence, none of the steps logically require the AdS/CFT conjecture for their justification.

Higher derivative invariants in four dimensional \U0001d4a9 = 3 Poincaré supergravity

In this paper we use the superconformal approach to derive the higher derivative action for \U0001d4a9 = 3 Poincaré supergravity in four space-time dimensions. We first study the coupling of \U0001d4a9 = 3 vector multiplets to conformal supergravity. Thereafter we combine it with the pure \U0001d4a9 = 3 conformal supergravity action and use a minimum of three vector multiplets as compensators to arrive at Poincaré supergravity with higher derivative corrections. We give a general prescription on how to eliminate the auxiliary fields in an iterative manner and obtain the supergravity action order by order in derivatives. We also show that the truncation of the action at fourth order in derivatives is a consistent truncation.

Scalar Curvature, Entropy, and Generalized Ricci Flow

AbstractWe derive a family of weighted scalar curvature monotonicity formulas for generalized Ricci flow, involving an auxiliary dilaton field evolving by a certain reaction–diffusion equation motivated by renormalization group flow. These scalar curvature monotonicities are dual to a new family of Perelman-type energy and entropy monotonicity formulas by coupling to a solution of the associated weighted conjugate heat equation. In the setting of Ricci flow, we further obtain a new family of convex Nash entropies and pseudolocality principles.

Gas sensitive performance and mechanism of multiferroic BiFeO3 under thermal-magnetic synergetic excitation

In this study, multiferroic BiFeO3 particles with size of ∼ 50 nm and good crystallinity were prepared via a simple sol–gel method and annealing. And the volatile organic compounds (VOCs) sensing properties of BiFeO3 sensor were measured under both traditional thermal excitation and synergetic thermal-magnetic excitation. In particular, auxiliary magnetic field was first introduced into testing environment. The results shows that the optimum operating temperature of the sensor decreases 10℃ by introducing magnetic field, and the sensor shows three times faster response speed and diverse selectivity with best response to n-butanol under thermal excitation while butanone under thermal-magnetic excitation. In addition, the sensor has response value of 1.25 to 1 ppm n-butanol, indicating the possibility of detecting low concentration of toxic gases. The effect of magnetic field on multiferroic BiFeO3 sensor can be divided into three aspects: decrease of defects on domain wall, excitation of testing gas molecules with asymmetry electron cloud distributions and activation of surface-absorbed oxygen species with unpaired electrons.

Utility of Particle Swarm Optimization in Statistical Population Reconstruction

Statistical population reconstruction models based on maximum likelihood and minimum chi-square objective functions provide a robust and versatile approach to estimating the demographic dynamics of harvested populations of wildlife. These models employ numerical optimization techniques to determine which set of model parameters best describes observed age-at-harvest, catch-effort, and other auxiliary field data. Although numerous optimization methods have been used in the past, the benefits of using particle swarm optimization (PSO) have yet to be explored. Using a harvested population of North American river otter (Lontra canadensis) in Indiana as a case study, we investigated the performance of population reconstruction using particle swarm optimization, spectral projected gradient (SPG), Nelder–Mead, and Broyden–Fletcher–Goldfarb–Shanno (BFGS) methods. We used Monte Carlo studies to simulate populations under a wide range of conditions to compare the relative performance of population reconstruction models using each of the four optimization methods. We found that using particle swarm optimization consistently and significantly improved model stability and precision when compared with other numerical optimization methods that may be used in statistical population reconstruction. Given that these models are frequently used to guide management decisions and set harvest limits, we encourage management agencies to adopt this more precise method of estimating model parameters and corresponding population abundance. These results illustrate the benefits of using particle swarm optimization, caution against relying on the results of population reconstruction based on optimization methods that are highly dependent on initial conditions, and reinforce the need to ensure model convergence to a global rather than a local maximum.

Field‐Free Spin‐Orbit Torque Switching in Synthetic Ferro and Antiferromagents with Exchange Field Gradient

AbstractDeterministic switching of perpendicularly magnetized synthetic antiferromagnets using spin‐orbit torque (SOT) usually requires an in‐plane auxiliary magnetic field, which limits its practical applications. Here, an exchange field gradient is introduced into perpendicularly magnetized synthetic ferro‐ and antiferromagnets (SFs and SAFs) through the insertion of a slightly wedged Ru between two thin ferromagnetic layers, which induces field‐free switching of perpendicular SFs and SAFs with a switching ratio up to 81% regardless of the nature of the coupling. Temperature‐dependent measurement shows a robust field‐free switching even at low temperature. The experimental results show that the field‐free switching ratio and the effective SOT field are directly related to the exchange field gradient. The theoretical model and numerical simulation indicate that the dynamic noncollinear spin textures induced by the exchange field gradient lead to the field‐free switching, while the sign of the exchange field gradient determines the field‐free switching polarity. It is further revealed that the SOT efficiency is positively correlated with the antiferromagnetic exchange field for both Ru wedged and non‐wedged samples. These results provide a new avenue for simultaneously achieving field‐free switching and high SOT efficiency of perpendicularly magnetized SAFs for highly stable, high‐density, low‐stray‐field, and low‐power magnetic memory devices.

Higher Order CPML for Leapfrog Complying-Divergence Implicit FDTD Method and Its Numerical Properties

The leapfrog complying-divergence implicit finite-difference time-domain (CDI-FDTD) method is an implicit scheme that is unconditionally stable involving the simplest and most efficient leapfrog update procedures with minimum floating-point operations (flops). Moreover, the method possesses complying divergence satisfying Gauss’s law, while other methods, including the leapfrog alternating direction implicit (ADI)-FDTD counterpart, do not. These desirable features make the leapfrog CDI-FDTD useful for electromagnetic simulations when the unconditional stability is to be exploited. In this article, a higher order convolutional perfectly matched layer (CPML) for leapfrog CDI-FDTD is developed and implemented for simulating open space problems. To formulate the CPML for leapfrog CDI-FDTD, we have carefully considered the order of CPML update along with proper use of main and auxiliary fields to retain the unconditional stability and complying divergence. The proposed CPML for leapfrog CDI-FDTD remains stable beyond the Courant time step as ascertained through von Neumann analysis. By comparing the flops and computation time, the leapfrog CDI-FDTD is shown to be most efficient among common implicit FDTD methods with CPML. The formulation of numerical divergence for higher order CPML is also presented. Simulation results show that the proposed higher order CPML has many advantages of simplicity, complying divergence, and high absorption efficiency.

Instanton gas approach to the Hubbard model

In this paper, we consider a path integral formulation of the Hubbard model based on a Hubbard-Stratonovich transformation that couples the auxiliary field to the local electronic density. This decoupling is known to have a saddle-point structure that shows a remarkable regularity: The field configuration at each saddle point can be understood in terms of a set of elementary field configurations localized in space and imaginary time which we coin instantons. The interaction between instantons is short ranged. Here, we formulate a classical partition function for the instanton gas that has predictive power. For a given set of physical parameters, we can predict the distribution of instantons and show that the instanton number is sharply defined in the thermodynamic limit, thereby defining a unique dominant saddle point. Decoupling in the charge channel conserves SU(2) spin symmetry for each field configurations. Hence, the instanton approach provides an SU(2) spin-symmetric approximation to the Hubbard model. It fails, however, to capture the magnetic transition inherent to the Hubbard model on the honeycomb lattice despite being able to describe local moment formation. In fact, the instanton itself corresponds to local moment formation and concomitant short-ranged antiferromagnetic correlations. This aspect is also seen in the single particle spectral function that shows clear signs of the upper and lower Hubbard bands. Our instanton approach bears remarkable similarities to local dynamical approaches, such as dynamical mean-field theory, in the sense that it has the unique property of allowing for local moment formation without breaking the SU(2) spin symmetry. In contrast to local approaches, it captures short-ranged magnetic fluctuations. Furthermore, it also offers possibilities for systematic improvements by taking into account fluctuations around the dominant saddle point. Finally, we show that the saddle point structure depends upon the choice of lattice geometry. For the square lattice at half filling, the saddle-point structure reflects the itinerant to localized nature of the magnetism as a function of the coupling strength. The implications of our results for Lefschetz thimble approaches to alleviate the sign problem are also discussed.

The Fokker–Planck formalism for closed bosonic strings

AbstractEvery Riemann surface with genus g and n punctures admits a hyperbolic metric, if 2g − 2 + n > 0. Such a surface can be decomposed into pairs of pants whose boundaries are geodesics. We construct a string field theory for closed bosonic strings based on this pants decomposition. In order to do so, we derive a recursion relation satisfied by the off-shell amplitudes, using Mirzakhani’s scheme for computing integrals over the moduli space of bordered Riemann surfaces. The recursion relation can be turned into a string field theory via the Fokker–Planck formalism. The Fokker–Planck Hamiltonian consists of kinetic terms and three-string vertices. Unfortunately, the worldsheet BRST symmetry is not manifest in the theory thus constructed. We will show that the invariance can be made manifest by introducing auxiliary fields.

Trends of Neutron Skins and Radii of Mirror Nuclei from First Principles.

The neutron skin of atomic nuclei impacts the structure of neutron-rich nuclei, the equation of state of nucleonic matter, and the size of neutron stars. Here we predict the neutron skin of selected light- and medium-mass nuclei using coupled-cluster theory and the auxiliary field diffusion MonteCarlo method with two- and three-nucleon forces from chiral effective field theory. We find a linear correlation between the neutron skin and the isospin asymmetry in agreement with the liquid-drop model and compare with data. We also extract the linear relationship that describes the difference between neutron and proton radii of mirror nuclei and quantify the effect of charge symmetry breaking terms in the nuclear Hamiltonian. Our results for the mirror-difference charge radii and binding energies per nucleon agree with existing data.

Effect of auxiliary longitudinal magnetic field on overlapping deposition of wire arc additive manufacturing

Effect of auxiliary longitudinal magnetic field on overlapping deposition of wire arc additive manufacturing

Релятивистская модель межатомных взаимодействий

In this paper, we propose a method for relativistic description of the dynamics of systems of interacting particles through an auxiliary field which in the static mode is equivalent to given interatomic potentials, and in the dynamic mode is a classical relativistic field. It has been established that for static interatomic potentials of a general form, the auxiliary field is a composition of elementary fields satisfying the Klein-Gordon type equations. Each elementary field is characterized by a complex parameter which is an analogue of the real mass in the Klein-Gordon equation. The interaction between particles through an auxiliary field is nonlocal both in spatial variables and in time. The qualitative properties of solutions to equations describing the auxiliary field are studied. Relativistic mechanisms of both the thermodynamic behavior and synergetic effects in few-particle systems have been established.

Optical manipulation: from fluid to solid domains

Light carries energy and momentum, laying the physical foundation of optical manipulation that has facilitated advances in myriad scientific disciplines, ranging from biochemistry and robotics to quantum physics. Utilizing the momentum of light, optical tweezers have exemplified elegant light–matter interactions in which mechanical and optical momenta can be interchanged, whose effects are the most pronounced on micro and nano objects in fluid suspensions. In solid domains, the same momentum transfer becomes futile in the face of dramatically increased adhesion force. Effective implementation of optical manipulation should thereupon switch to the “energy” channel by involving auxiliary physical fields, which also coincides with the irresistible trend of enriching actuation mechanisms beyond sole reliance on light-momentum-based optical force. From this perspective, this review covers the developments of optical manipulation in schemes of both momentum and energy transfer, and we have correspondingly selected representative techniques to present. Theoretical analyses are provided at the beginning of this review followed by experimental embodiments, with special emphasis on the contrast between mechanisms and the practical realization of optical manipulation in fluid and solid domains.

ЗАБЕЗПЕЧЕННЯ УПРАВЛІННЯ РОЗГОРТАННЯМ МОБІЛЬНОЇ КОМПОНЕНТИ СИСТЕМИ ЗВ’ЯЗКУ З’ЄДНАНЬ ТА ЧАСТИН НАЦІОНАЛЬНОЇ ГВАРДІЇ УКРАЇНИ ЦИФРОВИМИ РАДІОЗАСОБАМИ

The capabilities of modern Harris RF-7800S-TR digital radios for managing communication units are considered. A comparative analysis of the capabilities of the Motorola DP4800 and Harris RF-7800S-TR radio stations was carried out in providing control over the deployment of the mobile communication center of the auxiliary control point of the territorial control of the National Guard of Ukraine. Proposed recommendations for the implementation of the topology of the Harris RF-7800S-TR radio station programming file for the management of the process of deploying a field communication node on one operating frequency with the separation of all radio networks and ensuring their simultaneous operation independently of each other and with access only to the appropriate management levels. The research results make it possible to develop an innovative frequency plan for the deployment control system of the auxiliary control point field communication node. At the same time, all radio stations operate on the same frequency, using different positions of the radio station channel switch. Separation of radio networks is temporary, and access to radio networks is carried out using various tangents, the functions of which are programmed in advance. Thus, the modern Harris RF-7800S-TR digital radio station, which is in service with NSU units, allows for reliable management of the deployment of a field communication node with the fulfillment of all requirements for security, communication security, and with minimal expenditure of material resources, and the conducted class on the implementation of the topology of the radio station programming file will provide the most effective training of communication specialists for positions in the military.

COMPARISON OF THE VIOLONCELLO CURRICULUMS OF STATE CONSERVATORIES MUSIC AND BALLET MIDDLE SCHOOLS AND HIGH SCHOOLS OF MUSIC AND PERFORMING ARTS

Her konservatuvar yönetimi, çalgı eğitimine aynı sınıfta başlatmamakta ve bu nedenle çalgı eğitime başlama yaşı ve sınıf düzeyi farklılık gösterebilmektedir. Konservatuvarlarda öğrencilerinin düzeyi de çalgıya başlama yaşına bağlı olarak değişmektedir. Bu çalışma, Türkiye’de eğitim veren devlet konservatuvarının müzik ve bale bölümlerinin ortaokul düzeyi ile müzik ve sahne sanatları bölümlerinin lise düzeyindeki yaylı çalgılar ana sanat dalı ve viyolonsel sanat dalı müfredatlarının benzerlik ve farklılıklarının karşılaştırılarak değerlendirilmesini içermektedir. Araştırma; konservatuvar eğitimi veren başlıca kurumlardan olan Ankara Hacettepe Üniversitesi, İzmir Dokuz Eylül Üniversitesi, Adana Çukurova Üniversitesi, Bursa Uludağ Üniversitesi, Aydın Adnan Menderes Üniversitesi Devlet Konservatuvarları ile Ankara Bilkent Üniversitesi Müzik ve Sahne Sanatları Fakültesi müfredatları ile sınırlı tutulmuştur. Genel tarama modeli ile yürütülen bu araştırma için veriler, ilgili kurumlarla yapılan görüşmelerle güncelliği onaylanan kurum web sitelerinden elde edilmiştir. Eksik bilgiler görüşme sırasında edinilmiştir. Araştırma sonucunda; ön hazırlık yapılarak planlanmış, mevcut duruma uygun olarak uygulamaya konmuş içerikler oluşturulduğu görülmektedir. Konservatuvarların alan ve yardımcı alan dersleri, konservatuvar tarafından teklif edilir. İlgili üniversite senatosunca kabul edildikten sonra Bakanlık tarafından onaylanarak Resmî gazetede yayınlanır ve uygulanır. Bu araştırmanın bulgularında uygulamaya konmuş bu içerikler sunulmuştur. Sunulan rapor; konservatuvarlar arasında geçiş yapmayı planlayan öğrenciler, aileleri ve eğitimcileri için nakil sınavlarına hazır bulunuşluk sağlamada kaynak niteliğindedir. Ayrıca, Üniversite ve birimlerin akredite olarak çalışmaları boyutunda değerli görülmektedir.

Effects of variable magnetic field assisted EDM on MRR and surface integrity of AZ80 magnesium

ABSTRACT Magnetic field-assisted electrical discharge machining (MFEDM) is [non-conventional method] employed to optimize and improve output parameters in electrical discharge machining (EDM) and has recently been of great interest to researchers. In EDM, a magnetic field is created by the movement of electrons in the plasma channel. It can be inferred from this theory that a rise in the magnetic field strength raises the plasma channel density and energy concentration. The present study aims to explore the effects of a variable magnetic field on the material removal rate (MRR) and surface integrity in MFEDM, comparing the variable magnetic field-assisted EDM to constant magnetic field-assisted EDM and conventional EDM. The AZ80 magnesium alloy was used for the workpiece which, due to its unique properties, has been widely used in many industries in recent years. Moreover, magnesium is paramagnetic and can yield different results in MFEDM. It was found that the external magnetic field increased the MRR by 58% and reduced the surface roughness in magnesium AZ80. In addition, the variable magnetic field outperformed the constant one in improving MRR and surface roughness. Also, the results showed that the auxiliary magnetic field is more effective on the surface roughness of ferromagnetic metals than paramagnetic metals.

Vacua by derivative corrections in mathcal {N} = 1 supergravity with matter multiplets

We study the vacuum structures of four-dimen-sional mathcal {N} = 1 old minimal supergravity with higher derivative corrections. We find that mathcal {N} = 1 supergravity with Riemann curvature square corrections and higher derivative matter chiral multiplets induces a non-trivial de Sitter vacuum, even in the absence of superpotentials. This vacuum generically breaks supersymmetry. We show that the auxiliary fields in the gravity and the chiral multiples play important roles to generate a potential in supersymmetric higher derivative theories.