Fermionic Space Research Articles

Full Lagrangian and Hamiltonian for quantum strings on AdS4 × CP 3 in a near plane wave limit

We find the full interacting Lagrangian and Hamiltonian for quantum strings in a near plane wave limit of AdS4 × \( \mathbb{C} \) P 3. The leading curvature corrections give rise to cubic and quartic terms in the Lagrangian and Hamiltonian that we compute in full. The Lagrangian is found as the type IIA Green-Schwarz superstring in the light-cone gauge employing a superspace construction with 32 grassmann-odd coordinates. The light-cone gauge for the fermions is non-trivial since it should commute with the supersymmetry condition. We provide a prescription to properly fix the κ-symmetry gauge condition to make it consistent with light-cone gauge. We use fermionic field redefinitions to find a simpler Lagrangian. To construct the Hamiltonian a Dirac procedure is needed in order to properly keep into account the fermionic second class constraints. We combine the field redefinition with a shift of the fermionic phase space variables that reduces Dirac brackets to Poisson brackets. This results in a completely well-defined and explicit expression for the full interacting Hamiltonian up to and including terms quartic in the number of fields.

Krajewski diagrams and the standard model

This paper provides a complete list of Krajewski diagrams representing the standard model of particle physics. We will give the possible representations of the algebra and the anomaly free lifts which provide the representation of the standard model gauge group on the fermionic Hilbert space. The algebra representations following from the Krajewski diagrams are not complete in the sense that the corresponding spectral triples do not necessarily obey to the axiom of Poincaré duality. This defect may be repaired by adding new particles to the model, i.e., by building models beyond the standard model. The aim of this list of finite spectral triples (up to Poincaré duality) is therefore to provide a basis for model building beyond the standard model.

Bosonization, coherent states and semiclassical quantum Hall skyrmions

We bosonize (2+1)-dimensional fermionic theory using coherent states. The gauge-invariant subspace ofboson–Chern–Simons Hilbert space is mapped to fermionic Hilbert space. This subspace isthen equipped with a coherent state basis. These coherent states are labelled by a dynamicspinor field. The label manifold could be assigned a physical meaning in terms of densityand spin density. A path-integral representation of the evolution operator in terms of thesephysical variables is given. The corresponding classical theory when restricted to LLL isdescribed by spin fluctuations alone and is found to be the NLSM with Hopf term. Theformalism developed here is suitable to study quantum Hall skyrmions semiclassicallyand/or beyond the hydrodynamic limit. The effects of Landau level mixing orthe presence of slowly varying external fields can also be easily incorporated.

Lüscher's μ-term and finite volume bootstrap principle for scattering states and form factors

We study the leading order finite size correction (Lüscher's μ-term) associated to moving one-particle states, arbitrary scattering states and finite volume form factors in ( 1 + 1 ) -dimensional integrable models. Our method is based on the idea that the μ-term is intimately connected to the inner structure of the particles, i.e., their composition under the bootstrap program. We use an appropriate analytic continuation of the Bethe–Yang equations to quantize bound states in finite volume and obtain the leading μ-term (associated to symmetric particle fusions) by calculating the deviations from the predictions of the ordinary Bethe–Yang quantization. Our results are compared to numerical data of the E 8 scattering theory obtained by truncated fermionic space approach. As a by-product it is shown that the bound state quantization does not only yield the correct μ-term, but also provides the sum over a subset of higher order corrections as well.

Anatomy of bubbling solutions

We present a comprehensive analysis of holography for the bubbling solutions of Lin-Lunin-Maldacena. These solutions are uniquely determined by a coloring of a 2-plane, which was argued to correspond to the phase space of free fermions. We show that in general this phase space distribution does not determine fully the 1/2 BPS state of N = 4 SYM that the gravitational solution is dual to, but it does determine it enough so that vevs of all single trace 1/2 BPS operators in that state are uniquely determined to leading order in the large N limit. These are precisely the vevs encoded in the asymptotics of the LLM solutions. We extract these vevs for operators up to dimension 4 using holographic renormalization and KK holography and show exact agreement with the field theory expressions.

Stretched horizon and entropy of superstars

Amongst the class of supergravity solutions found by Lin, Lunin and Maldacena, we consider pure and mixed state configurations generated by phase space densities in the dual fermionic picture. A one-to-one map is constructed between the phase space densities and piecewise monotonic curves, which generalize the Young diagrams corresponding to pure states. Within the fermionic phase space picture, a microscopic formula for the entropy of mixed states is proposed. Considering thermal ensembles, agreement is found between the thermodynamic and the proposed microscopic entropies. Furthermore, we study fluctuations in thermodynamic ensembles for the superstar and compare the entropy of these ensembles with the area of stretched horizons predicted by the mean fluctuation size.

Pair condensation in a finite Fermi system

The lowest seniority-zero eigenstates of an exactly solvable multilevel pairing Hamiltonian for a finite Fermi system are examined at different pairing regimes. After briefly reviewing the form of the eigenstates in the Richardson formalism, we discuss a different representation of these states in terms of the collective pairs resulting from the diagonalization of the Hamiltonian in a space of two degenerate time-reversed fermions. We perform a two-fold analysis by working both in the fermionic space of these collective pairs and in a space of corresponding elementary bosons. On the fermionic side, we monitor the variations which occur, with increasing the pairing strength, in the structure of both these collective pairs and the lowest eigenstates. On the bosonic side, after reviewing a fermion-boson mapping procedure, we construct exact images of the fermion eigenstates and study their wave function. The analysis allows a close examination of the phenomenon of pair condensation in a finite Fermi system and gives new insights into the evolution of the lowest (seniority-zero) excited states of a pairing Hamiltonian from the unperturbed regime up to a strongly interacting one.

Low-lyingJ=1states inCd106

The atomic nucleus {sup 106}Cd was studied via the {beta}-decay of {sup 106}In and using nuclear resonance fluorescence. The decay pattern of five J=1 states and precise lifetimes of three spin 1 states have been deduced. By combining both data sets a candidate for the quadrupole-octupole coupled 1{sup -} state was identified at 2825 keV. Only this state shows the decay pattern comparable with the known quadrupole-octupole coupled 1{sup -} states in the other even-even stable cadmium isotopes {sup 108-116}Cd. For the description of this collective state a good agreement with predictions of the Q-phonon approach using a fermionic configurational space and microscopic calculations on the basis of the random phase approximation was found.

On neutron number dependence of B(E1;0+ 1 → 1- 1) reduced transition probability

A neutron number dependence of the E1 0+ --> 1- reduced transition probability in spherical even--even nuclei is analysed within the Q--phonon approach in the fermionic space to describe the structure of collective states. Microscopic calculations of the E1 0+ --> 1- transition matrix elements are carried out for the Xe isotopes based on the RPA for the ground state wave function. A satisfactory description of the experimental data is obtained.

A New Boson Realization of the Two-Level Pairing Model in a Many-Fermion System and Its Classical Counterpart: -- The Role of the su(2) su(1,1)-Coherent State in the Schwinger Boson Representation for the su(2) su(2)-Algebra --

A new method for describing the two-level pairing model in a many-fermion system is presented. The basic idea comes from the Schwinger boson representation for the su(2) ⊗ su(2)-algebra, in which four kinds of boson operators govern the dynamics. It is well known that in the original fermion space, it is almost impossible to introduce any trial state for the variation except the BCS state in the framework of the mean field approximation. However, in the Schwinger boson representation, various trial states can be defined on the condition that the mean field approximation is useful. In these states, the su(2) ⊗ su(1, 1)-coherent state is mainly discussed in this paper.

Symmetric Spaces of Matter and Real Fermion Manifolds

The geometric algebra Cl3,1 generated by the Minkowski spacetime with signature {+++− } possesses a natural ternary partition which provides the Lie algebra of the standard model symmetry in an improved form. The symmetric spaces of matter embed a differentiable manifold of primitive idempotents which represents a real valued fermion space as an 8-dimensional real unitsphere in a 10-dimensional subspace with positive definite signature. The algebraic properties of the present theory of spacetime-matter are developed, beginning with the definiteness of the stabilizer algebra of neutrinos, investigating the orthogonality between fermions and neutrinos and ending with the curvature of the symmetric spaces of the strong force. The model brings together the quantum theory and relativity, as we conceive it at present, such that the standard model turns out to be a definite property of the spacetime algebra.

Complex matrix model and fermion phase space for bubbling AdS geometries

We study a relation between droplet configurations in the bubbling AdS geometries and a complex matrix model that describes the dynamics of a class of chiral primary operators in dual N=4 super Yang Mills (SYM). We show rigorously that a singlet holomorphic sector of the complex matrix model is equivalent to a holomorphic part of two-dimensional free fermions, and establish an exact correspondence between the singlet holomorphic sector of the complex matrix model and one-dimensional free fermions. Based on this correspondence, we find a relation of the singlet holomorphic operators of the complex matrix model to the Wigner phase space distribution. By using this relation and the AdS/CFT duality, we give a further evidence that the droplets in the bubbling AdS geometries are identified with those in the phase space of the one-dimensional fermions. We also show that the above correspondence actually maps the operators of N=4 SYM corresponding to the (dual) giant gravitons to the droplet configurations proposed in the literature.

The Richardson Hamiltonian in the strong coupling limit: new results from an application of the non-unitary Dyson mapping

Applications of the generalized Dyson mapping lead to non-Hermitian Hamiltonians when they are expressed in the convenient space of independent bosons and fermions. We show how this formalism may be applied to the Richardson model which has recently been demonstrated to be appropriate for the description of superconducting metallic grains. For the first time a perturbative calculation of the wave function and a time-dependent analysis become possible, very much facilitated by a proper application of degenerate perturbation theory for non-Hermitian operators. We briefly discuss the implications for the description of ultra-cold Fermi gases which may also be described within the same framework.

Superfield integrals in high dimensions

We present an efficient, covariant, graph-based method to integrate superfields over fermionic spaces of high dimensionality. We illustrate this method with the computation of the most general sixteen-dimensional Majorana-Weyl integral in ten dimensions. Our method has applications to the construction of higher-derivative supergravity actions as well as the computation of string and membrane vertex operator correlators.

The Lipkin Model in the su(M + 1)-Algebra for Many-Fermion System and Its Counterpart in the Schwinger Boson Representation

Following the Schwinger boson representation for the su(M+1)- and the su(N,1)-algebra presented by two of the present authors (J. da P. and M. Y.) and Kuriyama, a possible counterpart of the Lipkin model in the su(M+1)-algebra formulated in the fermion space is presented. The free vacuum, which plays a fundamental role in the conventional treatment of the Lipkin model, is generalized in a quite natural way, and further, the excited state generating operators such as the particle-hole pairs are also given in a natural scheme. As concrete examples, the cases of the su(2)-, su(3)- and the su(4)-algebra are discussed. Especially, the case of the su(4)-algebra is investigated in detail in relation to the nucleon pairing correlations and the high temperature superconductivity.

Quantum stopping times and quasi-left continuity

We study the general properties of quantum stopping times on Hilbert spaces equipped with a filtration. We define and investigate notions such as the spaces of anterior events, the spaces of strictly anterior events and above all we define the property S< T for two stopping times together with the notion of predictable quantum stopping times. It is well-known that the natural filtration of any normal martingale with the predictable representation property is quasi-left continuous; with the help of our new notions we prove that this property is actually an intrinsic property of the symmetric Fock space Φ over L 2( R +) . We also apply these definitions to the case of a non commutative stochastic base. We show, in this context, that the fermionic Fock space over L 2( R +) , the quasi-free boson and fermion spaces are also quasi-left continuous.

Treatment of backscattering in a gas of interacting fermions confined to a one-dimensional harmonic atom trap

An asymptotically exact many body theory for spin polarized interacting fermions in a one-dimensional harmonic atom trap is developed using the bosonization method and including backward scattering. In contrast to the Luttinger model, backscattering in the trap generates one-particle potentials which must be diagonalized simultaneously with the two-body interactions. Inclusion of backscattering becomes necessary because backscattering is the dominant interaction process between confined identical one-dimensional fermions. The bosonization method is applied to the calculation of one-particle matrix elements at zero temperature. A detailed discussion of the validity of the results from bosonization is given, including a comparison with direct numerical diagonalization in fermionic Hilbert space. A model for the interaction coefficients is developed along the lines of the Luttinger model with only one coupling constant $K$. With these results, particle densities, the Wigner function, and the central pair correlation function are calculated and displayed for large fermion numbers. It is shown how interactions modify these quantities. The anomalous dimension of the pair correlation function in the center of the trap is also discussed and found to be in accord with the Luttinger model.

Ising Field Theory in a Magnetic Field: Analytic Properties of the Free Energy

We study the analytic properties of the scaling function associated with the 2D Ising model free energy in the critical domain T→Tc, H→0. The analysis is based on numerical data obtained through the Truncated Free Fermion Space Approach. We determine the discontinuities across the Yang–Lee and Langer branch cuts. We confirm the standard analyticity assumptions and propose “extended analyticity;” roughly speaking, the latter states that the Yang–Lee branching point is the nearest singularity under Langer's branch cut. We support the extended analyticity by evaluating numerically the associated “extended dispersion relation.”

A New Bosonization Method for Photoexcited Electronic States and Its Application to Nonlinear Optical Responses

We derive a bosonized Hamiltonian for a semiconductor quantum well with a light field by a new bosonization method taking exactly into account the composite-particle effects of excitons. Then we apply the bosonized Hamiltonian to the four-wave-mixing (FWM) processes. The obtained Hamiltonian describes two-boson states corresponding to bound and unbound two-exciton states and guarantees exclusion of unphysical states, which cannot exist in the fermionic space due to the Pauli exclusion principle. Calculated results of the FWM signals are in good agreement with the experimental ones, and therefore, the bosonized Hamiltonian turns out to be able to describe two-exciton correlations effectively.

Pairing Model and Mixed State Representation. II: Grand Partition Function and Its Mean Field Approximation

In order to compare the approach of the mixed state representation of the pairing model with the exact evaluation of the grand partition function, we introduce the fermion space of a grand canonical ensemble. For the definition of the grand partition function, we adopt a quasi-spin space and evaluate its multiplicity. Then we show how to derive the mixed state representation, which yields results that are approximately the same as those of the thermal Hartree-Fock-Bogoliubov theory for the thermal equilibrium state, from the grand partition function under the mean field approximation. We compare numerical results of the mean field approximation with those obtained from the exact evaluation of the grand partition function. We find that the mean field approximation gives good results. However, we find a distinctive difference between the two sets of results in the condensed phase.