Bosonic Sector Research Articles

Path integrals of perturbative strings on curved backgrounds from string geometry theory

String geometry theory is one of the candidates of the nonperturbative formulation of string theory. In this paper, from the closed bosonic sector of string geometry theory, we derive path integrals of perturbative strings on all of the string backgrounds, ${G}_{\ensuremath{\mu}\ensuremath{\nu}}(x)$, ${B}_{\ensuremath{\mu}\ensuremath{\nu}}(x)$, and $\mathrm{\ensuremath{\Phi}}(x)$, by considering fluctuations around the string background configurations, which are parametrized by the string backgrounds.

Fundamental membranes and the string dilaton

We study the quantization of the bosonic sector of supermembrane theory in double dimensional reduction, in order to extract the dependence of the resulting world-sheet action on the string dilaton (which cannot be obtained from a purely kinematic reduction). Our construction relies on a Polyakov-type approach with all six metric components on the world-volume as independent quantum fields, and shows that the correct and unique answer is only obtained if the target-space dimension of the theory is restricted to the critical value (D = 11 for the supermembrane). As a corollary, our analysis implies that there are no analogs of the non-critical string for (super-)membrane theory.

SO(4) multicriticality of two-dimensional Dirac fermions

We study quantum multicritical behavior in a (2+1)-dimensional Gross-Neveu-Yukawa field theory with eight-component Dirac fermions coupled to two triplets of order parameters that act as Dirac masses, and transform as $(1,0) + (0,1)$ representation under the SO(4)$\simeq$SO(3)$\times$SO(3) symmetry group. This field theory is relevant to spin-1/2 fermions on honeycomb or $\pi$-flux lattices, for example, near the transition points between an $s$-wave superconductor and a charge-density wave, on one side, and N\'eel order, on the other. Two triplets of such order parameters always allow for a common pair of two other order parameters that would complete them to the maximal set of compatible (anticommuting) orders of five. We first derive a unitary transformation in the Nambu (particle-hole) space which maps any two such triplets, possibly containing some superconducting orders, onto purely insulating order parameters. This allows one to consider a universal SO(4) Gross-Neveu-Yukawa description of the multicriticality without any Nambu doubling. We then proceed to derive the renormalization-group flow of the coupling constants at one-loop order in $4-\epsilon$ space-time dimensions, allowing also a more general set of order parameters transforming under SO($n_a$)$\times$SO($n_b$). While for $n_a=n_b > 2 $ in the bosonic sector and with fermions decoupled there is a stable fixed point of the flow, the Yukawa coupling to fermions quickly leads to its elimination by a generic fixed-point collision in the relevant range of fermion flavor numbers $N_f$. This suggests the replacement of the critical behavior by a runaway flow in the physical case $n_a=n_b=3$. The structure of the RG flow at $n_a\neq n_b$ is also discussed, and some non-perturbative arguments in favor of the stability of the decoupled critical point when $n_a=3$ and $n_b=1$ in $D=2+1$ are provided.

Harmonic forms on asymptotically ADS metrics

In this paper we study the rotationally invariant harmonic cohomology of a two-parameter family of Einstein metrics g which admits a cohomogeneity one action of SU(2) × U(1) and has AdS asymptotics. Depending on the values of the parameters, g is either of NUT type, if the fixed-point locus of the U(1) action is zero-dimensional, or of bolt type, if it is two-dimensional. We find that if g is of NUT type then the space of SU(2)-invariant harmonic two-forms is three-dimensional and consists entirely of self-dual forms; if g is of bolt type it is four-dimensional. In both cases we explicitly determine a basis. The pair (g, F) for F a self-dual harmonic two-form is also a solution of the bosonic sector of 4D supergravity. We determine for which choices it is a supersymmetric solution and the amount of preserved supersymmetry.

Kinetic mixing, custodial symmetry, and a lower bound on the mass of a dark gauge boson

Abstract We consider the extension of the standard model by dark fields with an Abelian spontaneously broken gauge symmetry in a hidden dark matter scenario. The dimension-four gauge-invariant terms include a kinetic mixing term and a Higgs mixing term, and we show that, after spontaneous symmetry breaking, the tree-level relation $M^{2}_{W}=M^{2}_{\tilde{Z}} \cos ^{2} \tilde{\theta }_{w}$ holds and permits us to write the mixing angle induced by the kinetic mixing in the neutral massive gauge boson sector, θζ, in terms of the values of MZ, the weak mixing angle, and of the mass of the physical dark gauge boson ZD. At the loop level, a similar relation is obtained in the $\overline{MS}$ scheme. Using the result extracted from the global fit to electroweak precision data for the ratio $\rho _{0}=M^{2}_{W}/\hat{c}^{2}_{Z} M^{2}_{Z}\hat{\rho }$, we obtain the lower bound $M_{Z_{D}}\gt M_{Z}$ for the dark gauge boson mass at the $94\%$ confidence level. We argue that this lower bound holds in the general case of theories for physics beyond the standard model with an extra U(1) gauge factor subgroup, whenever the extended Higgs potential respects custodial symmetry.

Fermionic vacuum polarization induced by a non-Abelian vortex

In this paper, we analyze the fermionic condensate (FC) and the vacuum expectation value (VEV) of the energy–momentum tensor associated with an iso-spin-[Formula: see text] charged massive fermionic field induced by the presence of a [Formula: see text] vortex, taking into account the effect of the conical geometry produced by this object. We consider the vortex as an idealized topological defect, i.e. very thin, straight and carrying a magnetic flux running along its core. Besides the direct coupling of the fermionic field with the iso-vector gauge field, we also admit the coupling with the scalar sector of the non-Abelian vortex system, expressed as a vector in the three-dimensional iso-space. Due to this interaction, the FC is expressed as the sum of two contributions associated with the two different effective masses for the [Formula: see text] fermionic components of the iso-spin operator, [Formula: see text]. The VEV of the energy tensor also presents a similar structure. The vacuum energy density is equal to the radial and axial stresses. As to the azimuthal one, it is expressed in terms of the radial derivative of energy density. Regarding the magnetic flux, both the FC and the VEV of the energy–momentum tensor can be positive or negative. Another interesting consequence of the interaction with the bosonic sector, the FC and VEV of the energy–momentum tensor, presents different intensity for different values of the ratio between the scalar coupling constant and the mass of the fermionic field. This is a new feature presented by the system.

Stable bound orbits in microstate geometries

We show the existence of stable bound orbits for the massive and massless particles moving in the simplest microstate geometry spacetime in the bosonic sector of the five-dimensional minimal supergravity. In our analysis, reducing the motion of particles to a two-dimensional potential problem, we numerically investigate whether the potential has a negative local minimum.

How does geometry affect quantum gases?

In this work, we study the thermodynamic functions of quantum gases confined to spaces of various shapes, namely, a sphere, a cylinder and an ellipsoid. We start with the simplest situation, namely, a spinless gas treated within the canonical ensemble framework. As a next step, we consider noninteracting gases (fermions and bosons) with the usage of the grand canonical ensemble description. For this case, the calculations are performed numerically. We also observe that our results may possibly be applied to Bose–Einstein condensate and to helium dimer. Moreover, the bosonic sector, independently of the geometry, acquires entropy and internal energy greater than for the fermionic case. Finally, we also devise a model allowing us to perform analytically the calculations in the case of interacting quantum gases, and, afterwards, we apply it to a cubical box.

Killing-Yano Cotton currents

We discuss conserved currents constructed from the Cotton tensor and (conformal) Killing-Yano tensors (KYTs). We consider the corresponding charges generally and then exemplify with the four-dimensional Plebański-Demiański metric where they are proportional to the sum of the squares of the electric and the magnetic charges. As part of the derivation, we also find the two conformal Killing-Yano tensors of the Plebański-Demiański metric in the recently introduced coordinates of Podolsky and Vratny. The construction of asymptotic charges for the Cotton current is elucidated and compared to the three-dimensional construction in Topologically Massive Gravity. For the three-dimensional case, we also give a conformal superspace multiplet that contains the Cotton current in the bosonic sector. In a mathematical section, we derive potentials for the currents, find identities for conformal KYTs and for KYTs in torsionful backgrounds.

Spinning solutions for the bosonic M2-brane with C± fluxes

In this work we obtain classical solutions of the bosonic sector of the supermembrane theory with two-form fluxes associated to a quantized constant C± background. This theory satisfies a flux condition on the worldvolume that induces monopoles over it. Classically it is stable as it does not contain string-like spikes with zero energy in distinction with the general case. At quantum level the bosonic membrane has a purely discrete spectrum but the relevance is that the same property holds for its supersymmetric spectrum. We find for this theory spinning membrane solutions, some of them including the presence of a non-vanishing symplectic gauge connection defined on its worldvolume in different approximations. By using the duality found between this theory and the so-called supermembrane with central charges, rotating membrane solutions found in that case, are also solutions of the M2-brane with C± fluxes. We generalize this result to other embeddings. We find new distinctive rotating membrane solutions, some of them including the presence of a non-vanishing symplectic gauge connection defined on its worldvolume. We obtain numerical and analytical solutions in different approximations characterizing the dynamics of the membrane with fluxes C± for different ansätze of the dynamical degrees of freedom. Finally we discuss the physical admissibility of some of these ansätze to model the components of the symplectic gauge field.

On a structure of the one-loop divergences in 4D harmonic superspace sigma-model

We study the quantum structure of four-dimensional {{mathcal {N}}}=2 superfield sigma-model formulated in harmonic superspace in terms of the omega-hypermultiplet superfield omega . The model is described by harmonic superfield sigma-model metric g_{ab}(omega ) and two potential-like superfields L^{++}_{a}(omega ) and L^{(+4)}(omega ). In bosonic component sector this model describes some hyper-Kähler manifold. The manifestly {{mathcal {N}}}=2 supersymmetric covariant background-quantum splitting is constructed and the superfield proper-time technique is developed to calculate the one-loop effective action. The one-loop divergences of the superfield effective action are found for arbitrary g_{ab}(omega ), L^{++}_{a}(omega ), L^{(+4)}(omega ), where some specific analogy between the algebra of covariant derivatives in the sigma-model and the corresponding algebra in the {{mathcal {N}}}=2 SYM theory is used. The component structure of divergences in the bosonic sector is discussed.

1D Supergravity FLRW Model of Starobinsky

We study two homogeneous supersymmetric extensions for the f(R) modified gravity model of Starobinsky with the FLRW metric. The actions are defined in terms of a superfield R that contains the FLRW scalar curvature. One model has N = 1 local supersymmetry, and its bosonic sector is the Starobinsky action; the other action has N = 2, its bosonic sector contains, in additional to Starobinsky, a massive scalar field without self-interaction. As expected, the bosonic sectors of these models are consistent with cosmic inflation, as we show by solving numerically the classical dynamics. Inflation is driven by the R2 term during the large curvature regime. In the N = 2 case, the additional scalar field remains in a low energy state during inflation. Further, by means of an additional superfield, we write equivalent tensor-scalar-like actions from which we can give the Hamiltonian formulation.

Type- 3/2 seesaw mechanism

The type-I seesaw mechanism provides a natural explanation for tiny neutrino masses. The right-handed neutrino masses it requires are, however, too large to keep the Higgs boson mass at its measured value. We show that vector spinors, singlet leptons that are like right-handed neutrinos, generate tiny neutrino masses naturally through the exchange of spin-$1/2$ and spin-$3/2$ components. This one-step seesaw mechanism, which we call the type-$3/2$ seesaw, keeps the Higgs boson mass unchanged at one loop and gives cause therefore to no fine-tuning problem. If the on-shell vector spinor is a pure spin-$3/2$ particle, then it becomes a potential candidate for hidden dark matter which gets diluted due only to the expansion of the Universe. The type-$3/2$ seesaw provides a natural framework for the neutrino, Higgs boson, and dark matter sectors, with overall agreement with current experiments and observations.

One-loop renormalization of vector boson scattering with the electroweak chiral Lagrangian in covariant gauges

This work presents a first full one-loop computation of vector boson scattering (VBS) within the non-linear effective field theory given by the bosonic sector of the usually called electroweak chiral Lagrangian (EChL). The computation is performed in the most general case of covariant $R_\xi$ gauges and is compared through all this work with the Standard Model case, whose computation in these covariant gauges is also novel and is presented also here. The calculation of the one-loop VBS amplitude is performed using the diagrammatic method by means of the one-particle-irreducible (1PI) Green functions that are involved in these scattering processes. The central part of this work is then devoted to the renormalization of all the n-legs one-loop 1PI Green functions involved. This renormalization is performed in the most general off-shell case with arbitrary external legs momenta. We then describe in full detail the renormalization program, which within this context of the EChL, implies to derive all the counterterms for both the electroweak parameters, like boson masses and gauge couplings, and those for the EChL coefficients. These later are crucial for the renormalization of the new divergences typically appearing when computing loops with the lowest chiral dimension Lagrangian. We present here the full list of involved divergences and counterterms in the $R_\xi$ gauges and derive the complete set of renormalization group equations for the EChL coefficients. In the last part of this work, we present the EChL numerical results for the one-loop cross section in the WZ channel and compare them with the SM results.

A non-relativistic limit of M-theory and 11-dimensional membrane Newton-Cartan geometry

We consider a non-relativistic limit of the bosonic sector of eleven-dimensional supergravity, leading to a theory based on a covariant ‘membrane Newton-Cartan’ (MNC) geometry. The local tangent space is split into three ‘longitudinal’ and eight ‘transverse’ directions, related only by Galilean rather than Lorentzian symmetries. This generalises the ten-dimensional stringy Newton-Cartan (SNC) theory. In order to obtain a finite limit, the field strength of the eleven-dimensional four-form is required to obey a transverse self-duality constraint, ultimately due to the presence of the Chern-Simons term in eleven dimensions. The finite action then gives a set of equations that is invariant under longitudinal and transverse rotations, Galilean boosts and local dilatations. We supplement these equations with an extra Poisson equation, coming from the subleading action. Reduction along a longitudinal direction gives the known SNC theory with the addition of RR gauge fields, while reducing along a transverse direction yields a new non-relativistic theory associated to D2 branes. We further show that the MNC theory can be embedded in the U-duality symmetric formulation of exceptional field theory, demonstrating that it shares the same exceptional Lie algebraic symmetries as the relativistic supergravity, and providing an alternative derivation of the extra Poisson equation.

NNLO QCD corrections to diphoton production with an additional jet at the LHC

We calculate the NNLO QCD corrections to diphoton production with an additional jet at the LHC. Our calculation represents the first NNLO-accurate prediction for the transverse momentum distribution of the diphoton system. The improvement in the accuracy of the theoretical prediction is significant, by a factor of up to four relative to NLO QCD as estimated through scale variations. Our calculation is exact except for the finite remainder of the two-loop amplitude which is included at leading color. The numerical impact of this approximated contribution is small. The results of this work are expected to further our understanding of the Higgs boson sector and of the behavior of higher-order corrections to LHC processes.

Instanton worldlines in five-dimensional \u03a9-deformed gauge theory

We discuss the Bosonic sector of a class of supersymmetric non-Lorentzian five-dimensional gauge field theories with an SU(1, 3) conformal symmetry. These actions have a Lagrange multiplier which imposes a novel Ω-deformed anti-self-dual gauge field constraint. Using a generalised ’t Hooft ansatz we find the constraint equation linearizes allowing us to construct a wide class of explicit solutions. These include finite action configurations that describe worldlines of anti-instantons which can be created and annihilated. We also describe the dynamics on the constraint surface.

Kink scattering in a generalized Wess-Zumino model

In this paper, kink scattering in the dimensional reduction of the bosonic sector of a one-parameter family of generalized Wess-Zumino models with three vacuum points is discussed. The value of the model parameter determines the specific location of the vacua. The influence of the vacuum arrangements (evolving from three collinear vacua to three vacua placed at the vertices of an equilateral triangle) on the kink scattering is investigated. Two different regimes can be distinguished: in the first one, two symmetric BPS kinks/antikinks arise whereas in the second one a new different BPS kink/antikink emerges, with the exception of a three-fold rotational symmetry case, where the three topological defects are identical. The scattering between the two symmetric kinks is thoroughly analyzed. Two different scattering channels have been found: kink-kink reflection and kink-kink hybridization. In the last case, the collision between the two symmetric kinks gives rise to the third different kink. Resonance phenomena also appear allowing a vibrating kink to split into two symmetric kinks moving away.

Fermion–charged-boson stars

Fermion-boson stars are starlike systems composed of the ordinary nuclear matter of a neutron star and bosonic dark matter. The bosonic dark matter has typically been taken to be a complex scalar field. A natural extension is for the complex scalar field to be charged. We make the simplest extension and gauge the scalar field under U(1). We therefore study fermion-charged-boson stars. We make a detailed study of the stability of this system by computing critical curves over the whole of parameter space. We then study how the fermion and boson sectors contribute to the total mass of the star. Finally, we present mass-radius diagrams, showing that an increase in charge can lead to more massive and more compact stars.

Disentangling boosted Higgs Boson production modes with machine learning

Higgs Bosons produced via gluon-gluon fusion with large transverse momentum (pT ) are sensitive probes of physics beyond the Standard Model. However, high pT Higgs Boson production is contaminated by many production modes other than gluon-gluon fusion, including vector boson fusion, production of a Higgs boson in association with a vector boson, and production of a Higgs boson with a top-quark pair. By using modern machine learning techniques to analyze jet substructure and event information, we demonstrate the capability of machine learning to identify production modes accurately. These tools hold great discovery potential for boosted Higgs bosons produced via ggF, and may also provide additional information about the Higgs Boson sector of the Standard Model in extreme regions of phase space for other production modes.