Negative Coupling Constant Research Articles

CLASSICAL AND QUANTUM COMPARISON OF KINK AND BELL SOLITONS AS ZERO-BRANES

The self-interacting scalar field theory with the negative coupling constant gives rise to the bell-shaped solitary wave solution which can be interpreted as a massive Bose particle. We compare its properties with those of the kink solution (also known as the domain-wall potential) arisen in the theory with the positive constant introducing the simplest example of the spontaneous breaking of symmetry. We rule out the uniform p-brane action for the kink and bell solutions as the nonminimal point particles with curvature. When quantizing it as the theory with higher derivatives, it is shown that the appearing quantum equation has SU (2) dynamical symmetry group realizing the exact spin-coordinate correspondence. Finally, we calculate the quantum corrections to the masses of kink and bell bosons which cannot be obtained by means of the perturbation theory starting from the vacuum sector.

The first observation of a muonium–carbonyl adduct with a negative muon coupling constant

Muonium atom addition to cyclopent-4-ene-1,3-dione I leads to the adduct radical II; in contrast with all other muonium adducts of carbonyl (CO) compounds so far studied, in which the isotropic muon coupling is of positive sign, the temperature dependence of the muon coupling in II reveals that its sign is negative; this may be explained as a consequence of the electronic ‘push–pull’ interaction within the MuO–C–CC–CO system, which reduces the out-of-plane vibrational amplitude of the muon by increasing the MuO–C/MuOC partial π-bond character.

Solid-State High-Resolution1H and2D NMR Study of the Electron Spin Density Distribution of the Hydrogen-Bonded Organic Ferromagnetic Compound 4-Hydroxyimino-TEMPO

The electron spin density distribution at hydrogen atoms of 4-hydroxyimino-2,2,6,6-tetramethylpiperidin-1-yloxyl (4-hydroxyimino-TEMPO), which has recently been shown to act as a molecular ferromagnet at low temperature, was determined in the crystalline phase on the basis of the temperature dependence of the Fermi contact shifts in the magic angle spinning deuterium NMR spectrum to elucidate the mechanism of intermolecular magnetic interaction. There are two kinds of close contacts among neighboring radical molecules in the crystalline phase. An axial methyl hydrogen atom locates near a neighboring N−O radical group, and the hydroxyl group undergoes hydrogen bonding with another neighboring N−O radical group. The plus and minus signs of the observed hyperfine coupling constants AD of methyl deuteriums indicate that there are two different mechanisms for the electron spin density distribution. Equatorial CD3 groups show negative coupling constants (AD = −0.24 MHz) induced by an intramolecular spin polariz...

Correlated second-order perturbation studies of spin–spin nuclear coupling constants from CS-INDO molecular orbitals: polymethine compounds

A second-order double perturbation treatment, using both the electronic correlation and Fermi contact operators as perturbation terms, has been performed for the evaluation of the indirect couplings of protons and carbon-13 nuclei of even- and odd-membered polymethine chains (conjugated polyenes and cyanines), in the frame of the CS-INDO molecular orbital method. The effect of electronic correlation on the values computed for the contact terms produces a significant increase of the 1J and 3J couplings and a decrease of the 2J couplings, sometimes leading to negative coupling constants, but the nucleus s-density parameter sN2(0) of hydrogen or carbon-13 cannot be reduced to a unique value, valid everywhere.

Variational perturbation approach to resonance-state wave functions

The variational perturbation theory for wave functions, which has been shown to work well for bound states of the anharmonic oscillator, is applied to resonance states of the anharmonic oscillator with negative coupling constant. We obtain uniformly accurate wave functions starting from the bound states.

Solid State 1H-Mas-Nmr and Spin Densities on Protons of the Organic Ferromagnetic Tempo Derivatives

Electron spin densities on hydrogen atoms of 4-(arylmethyleneamino)-2,2,6,6-tetramethylpiperidin-1-oxyls (abbreviated as Ar-CH=N-TEMPO), which show ferromagnetic behavior at low temperatures, were determined in their crystal phases from the temperature dependence of the Fermi contact shift measured by high speed magic angle spinning proton nuclear magnetic resonance. This method revealed a large negative hyperfine coupling constant for the methyl and methylene protons, A = -1.00 MHz for Ar = p-C1-ph and A = -1.32 MHz for Ar = ph, and very small one for the aryl group protons, |A| < 0.01 MHz for p-Cl-ph and A = +0.04 MHz for ph. The observed negative hyperfine coupling constant (negative spin density) of methyl and methylene protons matches with spin alternation for the intermolecular spin polarization mechanism through the contact of methyl and/or methylene protons to adjacent N-O radical group. This contact potentially contributes to the intermolecular ferromagnetic interaction.

Multi-vortex solution in the Sutherland model

We consider the large-$N$ Sutherland model in the Hamiltonian collective-field approach based on the $1/N$ expansion. The Bogomol'nyi limit appears and the corresponding solutions are given by static-soliton configurations. They exist only for $l<1$, i.e. for the negative coupling constant of the Sutherland interaction. We determine their creation energies and show that they are unaffected by higher-order corrections. For $l=1$, the Sutherland model reduces to the free one-plaquette Kogut-Susskind model.

The Radical Ions of Dipleiadiene (Dicyclohepta[de,ij]naphthalene) and Its 12b,12c‐Homo Derivative. An ESR and ENDOR study

AbstractThe radical anions and the radical cations of dipleiadiene (dicyclohepta[de,ij]naphthalene; 1) and its 12b, 12c‐homo derivative 2 were characterized by ESR and ENDOR spectroscopy. Their singly occupied orbitals are related to the degenerate nonbonding MOs of a 16‐membered π‐perimeter. The π‐spin distribution over the perimeter is similar in the radical cations 1.+ and 2.+, and an analogous statement holds for the radical anions 1.− and 2.−. However, deviations of the π‐system from planarity lead to a decrease in the absolute values of the negative coupling constants of the perimeter protons in 2.+ and 2.− relative to those in 1.+ and 1.−. The hyperfine data for the perimeter protons in the radical ions correlate with the changes in 13C chemical shifts on passing from the neutral compounds to the corresponding diions. It is concluded from the coupling constants of the CH2 protons in the radical ions of 2 that the cation 2.+ exists in the methano‐bridged form (A) of the neutral 2 (and, presumably, also of the dication 22+), whereas the anion 2.− adopts the bisnorcaradiene form (B) of the dianion 22−.

121Sb Mössbauer Spectra of Hexafluorocumyl Alcohol Complexes of Sb(V), and of Sb(III) with Negative Quadrupole Coupling Constants

Abstract The antimony-121 Mössbauer spectra of antimony(V) complexes of hexafluorocumyl alcohol show that the oxygen atoms of the ligand attract 5s electrons of antimony atoms more than do chlorine atoms, but that the reverse is true for the 5pz electrons of the antimony atoms. The antimony(III) complexes of the same ligand exhibit large negative values of e2qQ, being only the second example of this negative sign.

DYSON-SCHWINGER EQUATIONS IN TERMS OF RANDOM WALKS: FOUR-FERMION INTERACTIONS

Quantum field theories of interacting fermions have been recently formulated in terms of directed random walks. Using this formulation, we derive a hierarchy of equations for the correlation functions of scalar N-component four-fermion theories. These follow from an analysis of the underlying random process, and from geometric considerations. Our equations are, as we show, equivalent to the standard Dyson-Schwinger equations of motion, and are a convenient starting point for nonperturbative investigations of four-fermion theories. In particular, we discuss the physical interpretation of the gap equation in the language of random walks, and show that, in both the N→0 and N→∞ limits, an interacting theory can be obtained only for a finely tuned negative bare coupling constant.

Construction of φ44 theory with negative coupling

Abstract We construct a non-trivial φ 4 4 model with a negative coupling constant, which is perturbatively known to be asymptotically free at short distances. We rotate the field on the complex plane to ensure the convergence of the functional integration for the negative coupling. Then the correlation functions exist and asymptotic freedom implies that they are non-trivial.

Contribution of the Weyl tensor to R2 inflation.

To study the generality of inflation from Lagrangians containing higher powers of curvature, the effects of the square of the Weyl tensor, ${C}^{2}\ensuremath{\equiv}{C}_{\ensuremath{\alpha}\ensuremath{\beta}\ensuremath{\gamma}\ensuremath{\delta}}{C}^{\ensuremath{\alpha}\ensuremath{\beta}\ensuremath{\gamma}\ensuremath{\delta}}$, on the ${R}^{2}$ inflationary scenario is considered. By examining the stability of radiation-dominated Robertson-Walker universes for small perturbations, the ${C}^{2}$ term is determined to enter with a negative coupling constant. Both analytical arguments and numerical methods are used to investigate the influence of the various derivatives of the anisotropy in a Bianchi type-I universe. While a small anisotropy only slightly modifies the standard ${R}^{2}$ scenario, for sufficiently large anisotropy the universe cannot isotropize and recollapse subsequently ensues. The critical values at which this behavior occurs is estimated. Thus, the inclusion of ${C}^{2}$ terms restricts the success of ${R}^{2}$ inflation.

Thermodynamic Bethe ansatz for RSOS scattering theories

Thermodynamic Bethe ansatz equations are suggested for RSOS scattering theories, which describe the scattering of kinks in the field theories, corresponding to the perturbations of the minimal CFT models. M p by relevant operators φ 1.3 with negative coupling constant. The equations turn to be of A p−2 type with a special choice of the mass terms. For the M 4 case (tricritical Ising) the equations are studied numerically. This gives high precision data for the Casimir energy of the finite-volume system. The analytic continuation in the coupling constant results in reasonable numerical data for positive values of coupling. The data support the interpretation of the positive-coupling field theory as the trajectory flowing from the tricritical Ising fixed-point to the critical Ising one.

C—H … O=C and C—H … H—C interactions in the side chains of 2-isopropylbenzaldehyde. A negative 5J(CHO,CH(CH3)2)

The 1H nuclear magnetic resonance spectra of 2-isopropylbenzaldehyde in CS2/C6D12 and acetone-d6 solutions provide the chemical shifts and coupling constants of all the protons. The long-range coupling constants involving the side-chain protons yield certain sums of the populations of the four putatively planar conformations. The o-anti conformers have a fractional population of 0.55(3) in the polar and of 0.49(3) in the nonpolar solvent. The conformers in which the methine C—H bond lies cis to the aldehyde group have a fractional population of 0.83(3) in both solutions. The close approach of the methine and aldehydic hydrogen atoms in one conformer is indicated by a negative proximate coupling constant between their protons of –0.39(1) Hz. The chemical shifts of the ring and of the side-chain protons are consistent with the conformer populations deduced from the long-range coupling constants and also with the indications that the side chains do not, on average, deviate from "coplanarity" with the ring by much more or less than in the parent compounds. The C—H … H—C and C—H … O=C interactions in the o-syn and o-anti conformers are most likely repulsive and of very similar magnitude and lead to a significant deshielding of the protons in these moieties. Molecular orbital computations are also reported and are an aid in estimating the populations of the individual conformers. The STO-3G MO structures have H … H and H … O distances well below the sums of the van der Waals radii of hydrogen and oxygen atoms in the conformers with the methine C—H bond placed cis to the aldehyde group, yet these are computed to be by far the most abundant by the STO-3G as well as by AM1 algorithms. Key words: 2-isopropylbenzaldehyde, conformations of; 2-isopropylbenzaldehyde, proximate spin–spin coupling constants in; MO calculations, STO-3G, and AM1 on 2-isopropylbenzaldehyde, 1H NMR and long-range spin–spin coupling constants in 2-isopropylbenzaldehyde.

Theory of local-phonon-coupled low-energy anharmonic excitation of the interstitial oxygen in silicon.

The previous model for the low-energy anharmonic excitation of the interstitial oxygen in silicon [D. R. Bosomworth, W. Hayes, A. R. L. Spray, and G. D. Watkins, Proc. R. Soc. London, Ser. A 317, 133 (1970)] is expanded so that the coupling to the local phonon is included. The result of the calculation explains the previously observed absorption peaks of $^{16}\mathrm{O}$ and $^{18}\mathrm{O}$ in the 30-, 1100-, and 1200-${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ bands, confirming the energy-level scheme and transition assignment of Bosomworth et al. The coupling significantly reduces the level separations of the low-energy anharmonic excitation, and plays an important role in explaining the $^{18}\mathrm{O}$ isotope peak shifts. A physical interpretation is given to the calculated negative coupling constant. The origin of the 517- and 1700-${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ bands is also discussed.

Vacuum Polarization and Scalar Field Effects in the Early Universe

Talcing into account vacuum polarization effects and a coherent massive scalar field we consider a singularity free cosmological model from which an intermediate inflationary stage follows quite naturally. According to the ideas of Tryon, Fomin, Zeldovich and others on the spontaneous creation of an universe by a quantum process the newly created universe must be closed. Its evolution starts from a finite initial value a of the order of the Planck length with a zero velocity ho = 0 (h - Hubble parameter). Therefore, in this moment an effective source term not fulfilling the strong energy condition must be dominant. It can originate fron a coherent massive scalar field (mass m) with zero kinetic energy and/or the vacuum polarization (considered here in the form of a modified gravitational Lagrangian with quadratic terms of the Ricci scalar). The corresponding general Lagrangian reads (c = h =1) where ∝ is a negative coupling constant and Lmat is the Lagrangian of other possible existing matter. Both the massive scalar field and the vacuum polarization effects drive the universe to expand exponentially for a definite time interval depending on the initial radius a0 and the parameters m and ∝, during which all other matter being originally present is diluted. The following small oscillations superimposed on the dust-like power law behaviour of the scale factor cause an intensive particle production, and the universe heats up to a radiation dominated Friedmann universe. This process must terminate before baryogenesis. The matching of the different phases of the cosmological evolution and the requirement to fit the parameters of the observed universe lead to a definite parameter range for m and |∝| well below the Planck values. In consequence the present mass density must be equal to the critical one (Ω = 1) with high accuracy.

The (φ 4)3 + 1 theory with infinitesimal bare coupling constants

We study the (φ4)3 + 1 theory by means of a variational method improved with a BCS-type vacuum state. We examine the theory with both negative and positive infinitesimal bare coupling constants, where the theory has been suggested to exist nontrivially and stably in the infinite ultraviolet cutoff limit. When the cutoff is sent to infinity, we find the instability of the vacuum energy at the end point value of the variational parameter in the case of the negative bare coupling constant. For the positive bare coupling constant, we can renormalize the vacuum energy without using the extremal condition with respect to the variational mass parameter. We do not find an instability for the whole range of parameters including the end point. We still have a possibility that the theory with this bare coupling constant is nontrivial and stable.

On the new phase in λφ4

We prove that the recently discovered phase with positive bare coupling constant and infinite mean-field renormalization in λφ 4 is not a proper new phase. Its gaussian effective potential turns out to be equivalent to the gaussian effective potential for the composite operator :λBφ 2 ( x): calculated in the precarious phase (i.e. negative bare coupling constant and no mean-field renormalization). The N = ∞ exactly soluble Gross-Neveu model is usede as a guide.

Valence fluctuation and Kondo effect in noncubic Ce-transition metal compounds (invited)

In the compounds between cerium and transition metals, with an almost filled d band, the electronegativity difference between the constituents can lead to a position of the Fermi level compared to the 4f state which strongly depends on the stoichiometry. The following states of cerium are then expected: magnetic 3+state, 3+state with Kondo effect, and intermediate valence state. The various noncubic compounds of the Ce-Ni and Ce-Pt systems, which are presented in this paper, are very interesting because all these Ce states are observed. The interest of these alloys is enhanced because of their low symmetry which allows one to observe the anisotropic effects resulting from the hybridization of the 4f state with the conduction band; these properties cannot be observed in the cubic compounds such as CeSn3, CePd3, CeAl2. Because of the large difference of behavior between the isomorphous equiatomic CeNi and CePt compounds, a continuous evolution from a Ce3+ magnetic state to an intermediate valence state is observed in the CeNixPt1−x pseudobinary compounds. These compounds are among the best examples of a ferromagnetic dense Kondo system in which the variation of the Curie temperature TC and of the Kondo temperature TK as a function of the Ni content are similar to those predicted in the Kondo lattice model when ‖Γn(EF)‖ increases (Γ is the negative coupling constant between the 4f shell and the conduction band).

Pressure effects in CeNi xPt 1-x dense kondo ferromagnets

Magnetic measurements have been carried out under hydrostatic pressures up to 6 kbar in orthorhombic CeNi x Pt 1− x dense Kondo ferromagnets with x = 0, 0.5 and 0.8. For all compounds a decrease of the Ce magnetic moment is observed. This reduction, very weak in CePt, is huge (35% in 6 kbar) for x = 0.8. On the Curie temperature T C the pressure effect is similar to an increase of the Ni content x: d ln T C/d p is +1.5×10 -2, 0.0 and -1.3×10 -2 respectively for x = 0, 0.5, 0.8. The application of pressure leading to an increase of the product ¦Γ n( E F)¦(Γ being the negative coupling constant between the 4f electron and the conduction band), the observed results give a clear confirmation of the Kondo lattice model which predicts that T C passes through a maximum whereas the Kondo effect always increases with this product.