ShantanuT01/DACTYL-Pretraining huggingface dataset:
We critically discuss relaxation experiments in magnetic systems that can be characterized in terms of an energy barrier distribution, showing that proper normalization of the relaxation data is needed whenever curves corresponding to different temperatures are to be compared. We show how these normalization factors can be obtained from experimental data by using the $T \ln(t/\tau_0)$ scaling method without making any assumptions about the nature of the energy barrier distribution. The validity of the procedure is tested using a ferrofluid of Fe_3O_4 particles.
The ferrimagnetic spinel MnCr2S4 shows a variety of magnetic-field-induced phase transitions owing to bond frustration and strong spin-lattice coupling. However, the site-resolved magnetic properties at the respective field-induced phases in high magnetic fields remain elusive. Our soft x-ray magnetic circular dichroism studies up to 40 T directly evidence element-selective magnetic-moment reorientations in the field-induced phases. The complex magnetic structures are further supported by entropy changes extracted from magnetocaloric-effect measurements. Moreover, thermodynamic experiments reveal an unusual tetracritical point in the H-T phase diagram of MnCr2S4 due to strong spin-lattice coupling.
In the light of the gathering evidence for $\nu_{\mu}-\nu_{\tau}$ neutrino oscillations, coming in particular from the Super-Kamiokande data on atmospheric neutrinos, we re-analyze the unification of gauge and Yukawa couplings within the minimal supersymmetric extension of the Standard Model (MSSM). Guided by a range of different grand-unified models, we stress the relevance of large mixing in the lepton sector for the question of bottom-tau Yukawa coupling unification. We also discuss the dependence of the favoured value of $\tan\beta$ on the characteristics of the high-energy quark and lepton mass matrices. In particular, we find that, in the presence of large lepton mixing, Yukawa unification can be achieved for intermediate values of $\tan\beta$ that were previously disfavoured. The renormalization-group sensitivity to the structures of different mass matrices may enable Yukawa unification to serve as a useful probe of GUT models.
Transport measurements are one of the most widely used methods of characterizing small systems in chemistry and physics. When interactions are negligible, the current through quantum dots, nanowires, molecular junctions, and other submicron structures can be obtained using the Landauer formula. Meir and Wingreen derived an exact expression for the current that also applies in the presence of interactions. This powerful theoretical tool requires knowledge of the exact Green's function. So far, an approximation extending beyond direct finite-order perturbation theory is missing. Here, we provide general expressions for both the electric and thermal currents where we expand the self-energy to the lowest order (frequently dubbed the GW approximation) but keep contributions to all orders in this quantity. Moreover, we show that the electric current is conserved only when the self-energy and vertex corrections are correctly included. We demonstrate that our formulae capture important non-perturbative features and hence, provide a powerful tool in cases where the exact solution cannot be found.
Heavy even-even nuclei exhibit low-energy collective excitations that are separated in scale from the microscopic (fermion) degrees of freedom. This separation of scale allows us to approach nuclear vibrations within an effective field theory (EFT). In odd-mass nuclei collective and single-particle properties compete at low energies, and this makes their description more challenging. In this article we describe odd-mass nuclei with ground-state spin $I=\sfrac{1}{2}$ by means of an EFT that couples a fermion to the collective degrees of freedom of an even-even core. The EFT relates observables such as energy levels, electric quadrupole ($E2$) transition strengths, and magnetic dipole ($M1$) moments of the odd-mass nucleus to those of its even-even neighbor, and allows us to quantify theoretical uncertainties. For isotopes of rhodium and silver the theoretical description is consistent with data within experimental and theoretical uncertainties. Several testable predictions are made.
Fabrication and operation of simple solid state electrochromic devices using ethyl viologen diperchlorate in a polymer matrix is presented here. In-situ Raman and transmission/absorption studies have been done to establish the origin of bias induced color change, between a transparent and navy blue color, in the electrochromic device. The origin of bias induced color change has been attributed to the bias induced redox switching between its viologen dication and free redicle forms. Fundamental reason behind colour changes of viologen molecule has been established. In-situ UV-Vis spectra reveals that the navy blue color of the device under biased condition is not due to increase in the transparency corresponding to blue wavelength but due to suppression of the transparency corresponding to the complementary colors. Absorption modulation has been reported from the device with good ON/OFF contrast of the device.
The pair production rates for spin-zero and spin-$\frac{1}{2}$ particles are calculated on spaces of the form $M \times {\mathbb R}^{1,1}$ with $M$ corresponding to ${\mathbb R}^2$ (flat), $T^2$ (flat, compactified), $S^2$ (positive curvature) and $H^2$ (negative curvature), with and without a background magnetic field on $M$. The motivation is to elucidate the effects of curvature and background magnetic field. Contrasting effects for positive and negative curvature on the two cases of spin are obtained. For positive curvature, we find enhancement for spin-zero and suppression for spin-$\frac{1}{2}$, with the opposite effect for negative curvature.
We present black hole solutions in $2+1-$dimensional Einstein's theory of gravity coupled with Born-Infeld nonlinear electrodynamic and a massless self-interacting scalar field. The model has five free parameters: mass $M$, cosmological constant $\ell $, electric $q$ and scalar $r_{0}$ charges and Born-Infeld parameter $\beta $. To attain exact solution for such a highly non-linear system we adjust, i.e. finely tune, the parameters of the theory with the integration constants. In the limit $\beta \rightarrow 0$ we recover the results of Einstein-Maxwell-Scalar theory, obtained before. The self interacting potential admits finite minima apt for the vacuum contribution. Hawking temperature of the model is investigated versus properly tuned parameters. By employing this tuned-solution as basis, we obtain also a dynamic solution which in the proper limit admits the known solution in Einstein gravity coupled with self-interacting scalar field. Finally we establish the equations of a general scalar-tensor field coupled to nonlinear electrodynamics field\ in $2+1-$dimensions without searching for exact solutions.
Rocky planets are thought to comprise compounds of Mg and O as these are among the most abundant elements, but knowledge of their stable phases may be incomplete. MgO is known to be remarkably stable to very high pressure and chemically inert under reduced condition of the Earth's lower mantle. However, in 'icy' gas giants as well as in exoplanets oxygen may be a more abundant constituent (Ref. 1,2). Here, using synchrotron x-ray diffraction in laser-heated diamond anvil cells, we show that MgO and oxygen react at pressures above 94 GPa and T = 2150 K with the formation of the theoretically predicted I4/mcm MgO2 (Ref.3). Raman spectroscopy detects the presence of a peroxide ion (O22-) in the synthesized material as well as in the recovered specimen. Likewise, energy-dispersive x-ray spectroscopy confirms that the recovered sample has higher oxygen content than pure MgO. Our finding suggests that MgO2 may substitute MgO in rocky mantles and rocky planetary cores under highly oxidizing conditions.
We say that a two dimensional p-adic Galois representation of a number field F is weight two if it is de Rham with Hodge-Tate weights 0 and -1 equally distributed at each place above p; for example, the Tate module of an elliptic curve has this property. The purpose of this paper is to establish a variety of results concerning odd weight two representations of totally real fields in as great a generality as we are able. Most of these results are improvements upon existing results. Three of our main results are as follows. (1) We prove a modularity lifting theorem for odd weight two representations, extending a theorem of Kisin to include representations which are not potentially crystalline. (2) We show that essentially any odd weight two representation is potentially modular, following the ideas of Taylor. (3) We show that one can lift essentially any odd residual representation to a minimally ramified weight two p-adic representation, using some ideas of Khare-Wintenberger. As an application of these results we show that if rho is a sufficiently irreducible odd weight two p-adic representation of a totally real field F and either F has odd degree or rho is indecomposable at some finite place away from p then rho occurs as the Tate module of a GL_2-type abelian variety. This establishes some new cases of the Fontaine-Mazur conjecture.
Cool subdwarfs of types K and M are the fainter counterparts of cool main sequence dwarfs that dominate the Galactic population. In this paper we present the results of an optical speckle survey of 62 confirmed cool subdwarf systems within 60 pc. We have resolved two new companions and confirmed two previously known companions with separations 0\farcs13 to 3\farcs29. After including previously known wide companions and all known spectroscopic binaries, we determine the multiplicity rate of cool subdwarfs to be 26$\pm$6%, which is somewhat lower than comparable main sequence stars, which have a multiplicity rate of 37$\pm$5%. We find that only 3% of the cool subdwarfs surveyed have companions within 10 AU, 3% have companions between 10 and 100 AU, and 14% have companions beyond 100 AU. The other 6% of cool subdwarfs are spectroscopic binaries. This is very different from K/M dwarfs that have most companions (13%) at separations closer than 10 AU. However, because a search for close binaries among a large sample of nearby cool subdwarfs remains elusive, it is not yet settled whether or not the multiplicity rates are significantly different. Nonetheless, several different observational results and theories pointing to a possible dearth of subdwarf multiples are discussed.
Both pulsation and mass loss are commonly observed in stars and are important ingredients for understanding stellar evolution and structure, especially for massive stars. There is a growing body of evidence that pulsation can also drive and enhance mass loss in massive stars and that pulsation-driven mass loss is important for stellar evolution. In this review, I will discuss recent advances in understanding pulsation driven mass loss in massive main sequence stars, classical Cepheids and red supergiants and present some challenges remaining.
We study dual conformal transformations of minimal area surfaces in $AdS_5 \times S^5$ corresponding to holographic smooth Wilson loops and some other related observables. To act with dual conformal transformations we map the string solutions to the dual space by means of T-duality, then we apply a conformal transformation and finally T-dualize back to the original space. The transformation maps between string solutions with different boundary contours. The boundary contours of the minimal surfaces are not mapped back to the AdS boundary, and the regularized area of the surface changes.
Runaway thermonuclear burning of a layer of accumulated fuel on the surface of a compact star provides a brief but intense display of stellar nuclear processes. For neutron stars accreting from a binary companion, these events manifest as thermonuclear (type-I) X-ray bursts, and recur on typical timescales of hours to days. We measured the burst rate as a function of accretion rate, from seven neutron stars with known spin rates, using a burst sample accumulated over several decades. At the highest accretion rates, the burst rate is lower for faster spinning stars. The observations imply that fast (> 400 Hz) rotation encourages stabilization of nuclear burning, suggesting a dynamical dependence of nuclear ignition on the spin rate. This dependence is unexpected, because faster rotation entails less shear between the surrounding accretion disk and the star. Large-scale circulation in the fuel layer, leading to enhanced mixing of the burst ashes into the fuel layer, may explain this behavior; further numerical simulations are required to confirm.
We explicitly find the rate of exponential long-term convergence for the ruin probability in a level-dependent L\'evy-driven risk model, as time goes to infinity. Siegmund duality allows to reduce the pro blem to long-term convergence of a reflected jump-diffusion to its stationary distribution, which is handled via Lyapunov functions.
In this paper, the perpendicular magnetic anisotropy (PMA) is tailored by changing the thickness of the free layer with the objective of producing MTJ nano-pillars with smooth linear resistance dependence with both in-plane magnetic field and DC bias. We furthermore demonstrate how this linear bias dependence can be used to create a zero-threshold broadband voltage rectifier, a feature which is important for rectification in wireless charging and energy harvesting applications. By carefully balancing the amount of PMA acting in the free layer the measured RF to DC voltage conversion efficiency can be made as large as 11%.
Odd-parity magnetic and magnetic toroidal multipoles in the absence of both spatial-inversion and time-reversal symmetries are sources of multiferroic and nonreciprocal optical phenomena. We investigate electronic states caused by an emergent odd-parity magnetic quadrupole (MQ) as a representative example of magnetic odd-parity multipoles. It is shown that spontaneous ordering of the MQ leads to an antisymmetric spin-orbital polarization in momentum space, which corresponds to a spin-orbital momentum locking at each wave vector. By symmetry argument, we show that the orbital or sublattice degree of freedom is indispensable to give rise to the spin-orbital momentum locking. We demonstrate how the electronic band structures are modulated by the MQ ordering in the three-orbital system, in which the MQ is activated by the spin-dependent hybridization between the orbitals with different spatial parities. The spin-orbital momentum locking is related with the microscopic origin of cross-correlated phenomena, e.g., the magnetic-field-induced symmetric and antisymmetric spin polarization in the band structure, the current-induced distortion, and the magnetoelectric effect. We also discuss similar spin-orbital momentum locking in antiferromagnet where the MQ degree of freedom is activated through the antiferromagnetic spin structure in a sublattice system.
Integration by parts identities (IBPs) can be used to express large numbers of apparently different d-dimensional Feynman Integrals in terms of a small subset of so-called master integrals (MIs). Using the IBPs one can moreover show that the MIs fulfil linear systems of coupled differential equations in the external invariants. With the increase in number of loops and external legs, one is left in general with an increasing number of MIs and consequently also with an increasing number of coupled differential equations, which can turn out to be very difficult to solve. In this paper we show how studying the IBPs in fixed integer numbers of dimension d=n with $n \in \mathbb{N}$ one can extract the information useful to determine a new basis of MIs, whose differential equations decouple as $d \to n$ and can therefore be more easily solved as Laurent expansion in (d-n).
We present a multi-wavelength photometric catalog in the COSMOS field as part of the observations by the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS). The catalog is based on Hubble Space Telescope Wide Field Camera 3 (HST/WFC3) and Advanced Camera for Surveys (ACS) observations of the COSMOS field (centered at RA: $10^h00^m28^s$, Dec:$+02^{\circ}12^{\prime}21^{\prime\prime}$). The final catalog has 38671 sources with photometric data in forty two bands from UV to the infrared ($\rm \sim 0.3-8\,\mu m$). This includes broad-band photometry from the HST, CFHT, Subaru, VISTA and Spitzer Space Telescope in the visible, near infrared and infrared bands along with intermediate and narrow-band photometry from Subaru and medium band data from Mayall NEWFIRM. Source detection was conducted in the WFC3 F160W band (at $\rm 1.6\,\mu m$) and photometry is generated using the Template FITting algorithm. We further present a catalog of the physical properties of sources as identified in the HST F160W band and measured from the multi-band photometry by fitting the observed spectral energy distributions of sources against templates.
For $n\geq 3$, we study the existence and asymptotic properties of the fundamental solution for elliptic operators in nondivergence form, ${\mathcal L}(x,\partial_x)=a_{ij}(x)\partial_i\partial_j+b_k(x)\partial_k$, where the $a_{ij}$ have modulus of continuity $\omega(r)$ satisfying the square-Dini condition and the $b_k$ are allowed mild singularities of order $r^{-1}\omega(r)$. A singular integral is introduced that controls the existence of the fundamental solution. We give examples that show the singular drift $b_k\partial_k$ may act as a perturbation that does not dramatically change the fundamental solution of ${\mathcal L}^o=a_{ij}\partial_i\partial_j$, or it could change an operator ${\mathcal L}^o$ that does not have a fundamental solution to one that does.
We present recent Green's function Monte Carlo calculations of magnetic moments and M1 transitions in $A \leq 9$ nuclei, which include corrections arising from two-body meson-exchange electromagnetic currents. Two-body effects provide significant corrections to the calculated observables, bringing them in excellent agreement with the experimental data. In particular, we find that two-body corrections are especially large in the A=9, $T=3/2$ systems, in which they account for up to $\sim 20%$ ($\sim 40 %$) of the total predicted value for the $^9$Li ($^9$C) magnetic moment.
Context. Investigations of abundances of carbon and nitrogen in the atmospheres of evolved stars of open clusters may provide comprehensive information on chemical composition changes caused by stellar evolution. Aims. Our main aim is to increase the number of open clusters with determined carbon-to nitrogen and carbon isotope ratios. Methods. High-resolution spectra were analysed using a differential model atmosphere method. Abundances of carbon were derived using the C_2 Swan (0,1) band head at 5635.5 {\AA} (FEROS spectra) and the C_2 Swan (1,0) band head at 4737 {\AA} (UVES spectra). The wavelength interval 7980-8130 {\AA}, with strong CN features was analysed to determine nitrogen abundances and 12^C/13^C isotope ratios. The oxygen abundances were determined from the [Oi] line at 6300 {\AA}. Results. The average value of 12^C/13^C isotope ratios of Cr 261 is equal to 18 \pm 2 in four giants and to 12 \pm 1 in two clump stars; it is equal to 16 \pm 1 in four clump stars of the open cluster NGC 6253. The mean C/N ratios in Cr 261 and NGC 6253 are equal to 1.67 \pm 0.06 and 1.37 \pm 0.09, respectively. Conclusions. The 12^C/13^C and C/N values in Cr 261 and NGC 6253 within limits of uncertainties agree with the theoretical model of thermohaline-induced mixing as well as with the cool-bottom processing model
Stochastic fluctuations are central to the understanding of extinction dynamics. In the context of population models they allow for the description of the transition from the vicinity of a non-trivial fixed point of the deterministic dynamics to a trivial fixed point, where the population has become extinct. To characterize analytically the fluctuations of a given stochastic population model, one can operate within the so-called linear-noise approximation. Here the fluctuations are taken to be Gaussian, and the phenomenon of extinction is so rare as to be negligible, for all practical purposes. When the size of the population becomes small, non-Gaussian fluctuations are instead found. Two analytical schemes are in principle available to determine the nature of the distribution of associated fluctuations: the generalized van Kampen system-size expansion beyond the conventional order of approximation and a WKB-like method. Here we investigate the accuracy of these two different approximation schemes, with reference to a simple stochastic process that converges to the logistic equation in the deterministic limit.
Resistive relativistic magnetohydrodynamic (RRMHD) simulations are applied to investigate the system evolution of relativistic magnetic reconnection. A time-split Harten--Lan--van Leer method is employed. Under a localized resistivity, the system exhibits a fast reconnection jet with an Alfv\'{e}nic Lorentz factor inside a narrow Petschek-type exhaust. Various shock structures are resolved in and around the plasmoid such as the post-plasmoid vertical shocks and the "diamond-chain" structure due to multiple shock reflections. Under a uniform resistivity, Sweet--Parker-type reconnection slowly evolves. Under a current-dependent resistivity, plasmoids are repeatedly formed in an elongated current sheet. It is concluded that the resistivity model is of critical importance for RRMHD modeling of relativistic magnetic reconnection.
We study the permanent regimes of the reduced Vlasov-Maxwell system for laser-plasma interaction. A non-relativistic and two different relativistic models are investigated. We prove the existence of solutions where the distribution function is Boltzmannian and the electromagnetic variables are time-harmonic and circularly polarized.
Large deviation principle by the weak convergence approach is established for the stochastic nonlinear Schrodinger equation in one-dimension and as an application the exit problem is investigated.
In condensed matter physics, one of the major topics is to find out and classify interesting novel topological matters and phenomena. Topologically nontrivial systems can also be achieved by using periodical driving fields. On the other hand, ratchet effect can be used to collect useful work from fluctuations or realize directed transport in periodically-driven systems. Here, we promote a dimer chain by applying two mutually-perpendicular ac electric fields, and obtain an effective two-dimensional Hamiltonian in the low-frequency regime. We thereby derive quantum Floquet anomalous Hall (QFAH) conductance and then find a quantized ratchet effect in the resulting current along the chain. Our further analysis shows that these originate from the electric fields only. This lengthwise quantized ratchet effect without magnetic field should be useful to designing novel high-performance electronic applications.
In this letter, the authors present a study of the energetics and magnetic interactions in Fe doped ZnO clusters by ab-initio density functional calculations. The results indicate that defects under suitable conditions can induce ferromagnetic interactions between the dopant Fe atoms whereas antiferromagnetic coupling dominates in a neutral defect-free cluster. The calculations also reveal an unusual ionic state of the dopant Fe atom residing at the surface of the cluster, a feature that is important to render the cluster ferromagnetic.