Model Effective Field Theory Research Articles

The asymptotic D-state to S-state ratio of triton

At low energies, an effective field theory (EFT) with only contact interactions as well as three-body forces allow a detailed analysis of renormalization in a non-perturbative context and uncovers novel asymptotic behaviour. Triton as a three-body system, based on the EFT have been previously shown to provide representative binding energies, charge radii, S-wave scattering amplitude and asymptotic normalization constants for the 3H bound state system. Herein, EFT predictions of the asymptotic D-state to S-state ratio of triton are calculated to more fully evaluate the adequacy of the EFT model. Manifestly model-independent calculations can be carried out to high orders, leading to high precision.

A class of effective field theory models of cosmic acceleration

We explore a class of effective field theory models of cosmic accelerationinvolving a metric and a single scalar field. These models can be obtained by starting with a set of ultralight pseudo-Nambu-Goldstone bosons whose couplings to matter satisfy theweak equivalence principle, assuming that one boson is lighter thanall the others, and integrating out the heavier fields.The result is a quintessence model with matter coupling,together with a series of correction terms in the action in a covariant derivative expansion, with specific scalings for the coefficients.After eliminating higher derivative terms and exploiting the field redefinition freedom,we show that the resulting theory contains nine independent free functions of the scalar field when truncated at four derivatives. This is in contrast to the four free functions found insimilar theories of single-field inflation, where matter is notpresent. We discuss several different representations of the theorythat can be obtained using the field redefinition freedom.For perturbations to the quintessence field today on subhorizonlengthscales larger than the Compton wavelength of the heavy fields,the theory is weakly coupled and natural in the sense of t'Hooft. Thetheory admits a regime where the perturbations become modestly nonlinear, but very strongnonlinearities lie outside its domain of validity.

An effective field theory model for one-dimensional CH chains: effects at finite chemicalpotential, temperature and external Zeeman magnetic field

In this work we use an effective field theory model to investigate doped(CH)x chains under the influence of an external constant Zeeman magnetic fieldB0, at zero and finite temperature, in the mean-field approximationand beyond. We consider both homogeneous and inhomogeneousΔ(x) condensates and calculate the Pauli magnetization and the magnetic susceptibility of thesechains in various situations for the temperature and chemical potentials. We also brieflydiscuss the possibility of using these materials as partially polarized 1D organicconductors.

Measurement of the partial cross sectionsσTT,σLT, and(σT+ɛσL)of the1H(e,e′π+)nreaction in theΔ(1232)resonance

We report new precision p(e,e' pi+})n measurements in the Delta(1232) resonance at Q2 = 0.127(GeV/c)2 obtained at the MIT-Bates Out-Of-Plane scattering facility. These are the lowest, but non-zero, Q2 measurements in the pi+ channel. The data offer new tests of the theoretical calculations, particularly of the background amplitude contributions. The chiral effective field theory and Sato-Lee model calculations are not in agreement with this experiment.

Magnetic properties of 2D nano-islands II: Ising spin model with out-of-plane magnetic field

An Ising effective field theory model is presented to calculate the magnetic properties of 2D nano-islands on a nonmagnetic substrate, subject to an externally out-of-plane applied magnetic field. The system Hamiltonian contains nearest neighbor exchange interactions, single-atom magnetic anisotropies, and the Zeeman term. The calculations yield, in particular, the single site spin correlations, the magnetizations, and the isothermal susceptibilities, for the core and periphery domains of the nano-island. The choice of a spin S=1 for the atoms of the system permits the analysis of local spin fluctuations via the single site spin correlations. We investigate in this respect the effects due to the different magnetocrystalline anisotropies and reduced dimensionalities, for the core and periphery domains, and in particular the critical influence of the applied magnetic field. Detailed theoretical results are presented for the square and hexagonal lattice symmetries, with numerical applications for the 2D monolayer Co nano-islands on a Pt substrate. It is shown that the remarkable differences between the magnetic properties of the core and periphery domains in zero field are washed out when an out-of-plane field is applied. The applied field also provokes critical discontinuities for the spin correlations and magnetization reversals, for the core and periphery domains, which are especially evident for the hexagonal lattice nano-island in the range of fields of interest. The discontinuities and magnetization reversals occur over elementary temperature widths, and shift to lower temperatures with increasing field. The field-dependant isothermal susceptibilities show new features very different from those for the susceptibilities in zero field. The present Ising model does not show any blocking temperature transition to superparamagnetism.

ON THE EFFECTIVE EQUATION OF STATE OF DARK ENERGY

In an effective field theory model with an ultraviolet momentum cutoff, there is a relation between the effective equation-of-state of dark energy and the ultraviolet cutoff scale. It implies that a measure of the equation of state of dark energy different from minus one, ω ≠ -1, does not rule out vacuum energy as dark energy. It also indicates an interesting possibility that precise measurements of the infrared properties of dark energy can be used to probe the ultraviolet cutoff scale of effective quantum field theory coupled to gravity. In a toy model with a vacuum energy-dominated universe with a Planck scale cutoff, the dark energy effective equation of state is w eff ≈ -0.96.

Non-relativistic effective theory of dark matter direct detection

Dark matter direct detection searches for signals coming from dark matter scattering against nuclei at a very low recoil energy scale ∼ 10 keV. In this paper, a simple non-relativistic effective theory is constructed to describe interactions between dark matter and nuclei without referring to any underlying high energy models. It contains the minimal set of operators that will be tested by direct detection. The effective theory approach highlights the set of distinguishable recoil spectra that could arise from different theoretical models. If dark matter is discovered in the near future in direct detection experiments, a measurement of the shape of the recoil spectrum will provide valuable information on the underlying dynamics. We bound the coefficients of the operators in our non-relativistic effective theory by the null results of current dark matter direct detection experiments. We also discuss the mapping between the non-relativistic effective theory and field theory models or operators, including aspects of the matching of quark and gluon operators to nuclear form factors.

Gauge coupling flux thresholds, exotic matter and the unification scale in F-SU(5) GUT

We explore the gauge coupling relations and the unification scale in F-theory SU(5) GUT broken down to the Standard Model by an internal U(1)Y gauge flux. We consider variants with exotic matter representations which may appear in these constructions and investigate their role in the effective field theory model. We make a detailed investigation on the conditions imposed on the extraneous matter to raise the unification scale and make the color triplets heavy in order to avoid fast proton decay. We also discuss in brief the implications on the gaugino masses.

Exciting Gauge Field and Gravitons in Brane-Antibrane Annihilation

In this Letter we point out the inevitability of an explosive production of gauge field and gravity wave during an open string tachyon condensation in a cosmological setting, in an effective field theory model. We will be particularly studying a toy model of brane-antibrane inflation in a warped throat where inflation ends via tachyon condensation. We point out that a tachyonic instability helps fragmenting the homogeneous tachyon and excites gauge field and contributes to the stress-energy tensor which also feeds into the gravity waves.

Effective theory of the quantum Hall effect in AdS/CFT

Drawing on the connection with superconductivity, we give a simple AdS realization of the quantum Hall effect. The theory includes a statistical gauge field with a Chern-Simons term, in analogy with effective field theory models of the QHE.

Proton–proton fusion in pionless effective theory

The proton–proton fusion reaction, pp→de+ν, is studied in pionless effective field theory (EFT) with di-baryon fields up to next-to leading order. With the aid of the di-baryon fields, the effective range corrections are naturally resummed up to the infinite order and thus the calculation is greatly simplified. Furthermore, the low-energy constant which appears in the axial-current-di-baryon–di-baryon contact vertex is fixed through the ratio of two- and one-body matrix elements which reproduces the tritium lifetime very precisely. As a result we can perform a parameter free calculation for the process. We compare our numerical result with those from the accurate potential model and previous pionless EFT calculations, and find a good agreement within the accuracy better than 1%.

Neutron spin rotation inn→−dscattering

The neutron spin rotation induced by parity-violating (PV) components in the nucleon-nucleon potential is studied in $\stackrel{\ensuremath{\rightarrow}}{n}\text{\ensuremath{-}}d$ scattering at zero energy. Results are obtained corresponding to the Argonne ${v}_{18}$ two-nucleon and Urbana-IX three-nucleon strong-interaction potentials in combination with either the Desplanques-Donoghue-Holstein or pionless effective field theory models for the weak-interaction potential. We find that this observable is dominated by the contribution of the long-range part of the PV potential associated with pion exchange. Thus its measurement could provide a further constraint, complementary to that coming from measurements of the photon asymmetry in $\stackrel{\ensuremath{\rightarrow}}{n}\text{\ensuremath{-}}p$ radiative capture, on the strength of this component of the hadronic weak interaction.

WARPED COMPACTIFICATION ON SIGMA MODEL, SKYRMIONS IN SIX DIMENSIONS

We construct two distinct brane solutions in six dimensional effective field theory models. The CP 1 sigma model and the baby skyrmion realize warped compactification of the extra dimensions for negative bulk cosmological constant. Higher winding number solutions of the baby skyrmion are also presented.

Asymptotic freedom in massive Yang-Mills theory

An effective field theory model of the massive Yang-Mills theory is considered. Assuming that the renormalized coupling constants of 'nonrenormalizable' interactions are suppressed by a large scale parameter it is shown that in analogy to the non-Abelian gauge invariant theory the dimensionless coupling constant vanishes logarithmically for large values of the renormalization scale parameter.

Interactions of the solar neutrinos with the deuterons

Starting from chiral Lagrangians, possessing the SU(2)_L x SU(2)_R local chiral symmetry, we derive weak axial one-boson exchange currents in the leading order in the 1/M expansion (M is the nucleon mass). We apply these currents in calculations of the cross sections for the disintegration of the deuterons by the low energy neutrinos. The nuclear wave functions are derived from a variant of the OBEPQB potential and from the Nijmegen 93 and Nijmegen I nucleon-nucleon interactions. The comparison of our cross sections with those obtained within the pionless effective field theory and other potential model calculations shows that the solar neutrino-deuteron cross sections can be calculated within an accuracy of 3.3 %.

NEAR FORWARD pp ELASTIC SCATTERING AT LHC AND NUCLEON STRUCTURE

High energy pp and [Formula: see text] elastic scattering carried out at CERN ISR and SPS Collider and at Fermilab Tevatron are studied first in a model where the nucleon has an outer cloud and an inner core. Elastic scattering is viewed as primarily due to two processes: (a) diffraction scattering originating from cloud–cloud interaction; (b) a hard or large |t| scattering originating from one nucleon core scattering off the other via vector meson ω exchange, while their outer clouds interact independently. For small |t| diffraction dominates, but the hard scattering takes over as |t| increases. The ω-exchange amplitude shows that ω behaves like an elementary vector meson at high energy, contrary to a regge pole behavior. This behavior, however, can be understood in the nonlinear σ-model where ω couples to a topological baryonic current like a gauge boson, and the nucleon is described as a topological soliton. Further investigation shows that the underlying effective field theory model is a gauged Gell-Mann–Levy type linear σ-model that has not only the pion sector and the Wess–Zumino–Witten action of the nonlinear σ-model, but also a quark sector where quarks and antiquarks interact via a scalar field. The scalar field vanishes near the center of the nucleon, but rises sharply at some critical distance to its vacuum value fπ leading to a [Formula: see text] condensate analogous to a BCS condensate in superconductivity. The nucleon structure that emerges then is that the nucleon has an outer cloud of [Formula: see text] condensed ground state, an inner core of topological baryonic charge probed by ω, and a still smaller quark-bag containing massless valence quarks. Large |t|pp elastic scattering is attributed to valence quark–quark elastic scattering, which is taken to be due to the hard pomeron (BFKL pomeron with next to leading order corrections). The parameters in the model are determined by requiring that they satisfactorily describe the known asymptotic behavior of σ tot (s) and ρ(s), and the measured [Formula: see text] at [Formula: see text], 630 GeV, and 1.8 TeV. The model is then used to predict pp elastic differential cross-section at LHC at [Formula: see text] and |t| = 0–10 GeV 2. Our predicted dσ/dt at 14 TeV is found to be very different from those predicted by the impact-picture model and the eikonalized pomeron–reggeon model. Precise measurement of dσ/dt at LHC by the TOTEM group will be able to distinguish between these models. If our predicted dσ/dt is quantitatively confirmed, then it will indicate that various novel ideas developed to describe the nucleon combine and lead to a unique physical description of its structure.

Superheavy nuclei in a relativistic effective Lagrangian model

Isotopic and isotonic chains of superheavy nuclei are analyzed to search for spherical double shell closures beyond $Z=82$ and $N=126$ within the new effective field theory model of Furnstahl, Serot, and Tang for the relativistic nuclear many-body problem. We take into account several indicators to identify the occurrence of possible shell closures, such as two-nucleon separation energies, two-nucleon shell gaps, average pairing gaps, and the shell correction energy. The effective Lagrangian model predicts $N=172$ and $Z=120$ and $N=258$ and $Z=120$ as spherical doubly magic superheavy nuclei, whereas $N=184$ and $Z=114$ show some magic character depending on the parameter set. The magicity of a particular neutron (proton) number in the analyzed mass region is found to depend on the number of protons (neutrons) present in the nucleus.

Constraints on axial two-body currents from solar neutrino data

We briefly review recent calculations of neutrino-deuteron cross sections within the effective field theory and traditional potential model approaches. We summarize recent efforts to determine the counter term describing axial two-body currents, ${L}_{1A}$, in the effective field theory approach. We determine the counterterm directly from the solar neutrino data and find several, slightly different, ranges of ${L}_{1A}$ under different sets of assumptions. Our most conservative fit value with the largest uncertainty is ${L}_{1A}={4.5}_{\ensuremath{-}12}^{+18}{\phantom{\rule{0.3em}{0ex}}\text{fm}}^{3}$. We show that the contribution of the uncertainty of ${L}_{1A}$ to the analysis and interpretation of the solar neutrino data measured at the Sudbury Neutrino Observatory is significantly less than the uncertainty coming from the lack of having a better knowledge of ${\ensuremath{\theta}}_{13}$.

Pp ELASTIC SCATTERING AT LHC AND NUCLEON STRUCTURE

High energy elastic pp scattering at the Large Hadron Collider (LHC) at c.m. energy 14 TeV is predicted using the asymptotic behavior of σ tot (s) and ρ(s) known from dispersion relation calculations and the measured elastic [Formula: see text] differential cross-section at [Formula: see text]. The effective field theory model underlying the phenomenological analysis describes the nucleon as having an outer cloud of quark–antiquark condensed ground state, an inner core of topological baryonic charge of radius ≃ 0.44 F and a still smaller valence quark-bag of radius ≲ 0.1 F. The LHC experiment TOTEM (Total and Elastic Measurement), if carried out with sufficient precision from |t| = 0 to |t| > 10 GeV 2, will be able to test this structure of the nucleon.

Constraining URCA cooling of neutron stars from the neutron radius of208Pb

Recent observations by the Chandra observatory suggest that some neutron stars may cool rapidly, perhaps by the direct URCA process which requires a high proton fraction. The proton fraction is determined by the nuclear symmetry energy whose density dependence may be constrained by measuring the neutron radius of a heavy nucleus, such as 208Pb. Such a measurement is necessary for a reliable extrapolation of the proton fraction to the higher densities present in the neutron star. A large neutron radius in 208Pb implies a stiff symmetry energy that grows rapidly with density, thereby favoring a high proton fraction and allowing direct URCA cooling. Predictions for the neutron radius in 208Pb are correlated to the proton fraction in dense matter by using a variety of relativistic effective field-theory models. Models that predict a neutron (Rn) minus proton (Rp) root-mean-square radius in 208Pb to be Rn-Rp<0.20 fm have proton fractions too small to allow the direct URCA cooling of 1.4 solar-mass neutron stars. Conversely, if Rn-Rp>0.25 fm, the direct URCA process is allowed (by all models) to cool down a 1.4 solar-mass neutron star. The Parity Radius Experiment at Jefferson Laboratory aims to measure the neutron radius in 208Pb accurately and model independently via parity-violating electron scattering. Such a measurement would greatly enhance our ability to either confirm or dismiss the direct URCA cooling of neutron stars.