arXiv subjects

Muneto Nitta

Publications and source records attributed to Muneto Nitta.

At least 181 records · Page 10Linked to original sources

arXiv2017

Exact Resurgent Trans-series and Multi-Bion Contributions to All Orders

The full resurgent trans-series is found exactly in near-supersymmetric $\mathbb C P^1$ quantum mechanics. By expanding in powers of the SUSY breaking deformation parameter, we obtain the first and second expansion coefficients of the ground state energy. They are absolutely convergent series of nonperturbative exponentials corresponding to multi-bions with perturbation series on those background. We obtain all multi-bion exact solutions for finite time interval in the complexified theory. We sum the classical multi-bion contributions that reproduce the exact result supporting the resurgence to all orders. This is the first result in the quantum mechanical model where the resurgent trans-series structure is verified to all orders in nonperturbative multi-bion contributions.

hep-th↗

arXiv2017

Some exact Bradlow vortex solutions

We consider the Bradlow equation for vortices which was recently found by Manton and find a two-parameter class of analytic solutions in closed form on nontrivial geometries with non-constant curvature. The general solution to our class of metrics is given by a hypergeometric function and the area of the vortex domain by the Gaussian hypergeometric function.

hep-th↗

arXiv2017

Low-energy Effective Worldsheet theory of a non-Abelian vortex in high-density QCD Revisited: A regular gauge construction

Color symmetry is spontaneously broken in quark matter at high density as a consequence of di-quark condensations with exhibiting color superconductivity. Non-Abelian vortices or color magnetic flux tubes stably exist in the color-flavor locked phase at asymptotically high-density. The effective worldsheet theory of a single non-Abelian vortex was previously calculated in the singular gauge to obtain the ${\mathbb C}P^2$ model [ arXiv:0908.4470 , arXiv:0912.1352 ]. Here, we reconstruct the effective theory in a regular gauge without taking a singular gauge, confirming the previous results in the singular gauge. As a byproduct of our analysis, we find that non-Abelian vortices in high-density QCD do not suffer from any obstruction for the global definition of a symmetry breaking.

hep-ph↗

arXiv2017

Confinement of Half-quantized Vortices in Coherently Coupled Bose-Einstein Condensates: Simulating Quark Confinement in QCD

We demonstrate that the confinement of half-quantized vortices (HQVs) in coherently coupled Bose-Einstein condensates (BECs) simulates certain aspects of the confinement in $SU(2)$ quantum chromodynamics (QCD) in 2+1 space-time dimensions. By identifying the circulation of superfluid velocity as the baryon number and the relative phase between two components as a dual gluon, we identify HQVs in a single component as electrically charged particles with a half baryon number. Further, we show that only singlet states of the relative phase of two components can stably exist as bound states of vortices, that is, a pair of vortices in each component (a baryon) and a pair of a vortex and an antivortex in the same component (a meson). We then study the dynamics of a baryon and meson; baryon is static at the equilibrium and rotates once it deviates from the equilibrium, while a meson moves with constant velocity. For both baryon and meson we verify a linear confinement and determine that they are broken, thus creating other baryons or mesons in the middle when two constituent vortices are separated by more than some critical distance, resembling QCD.

cond-mat.quant-gas↗

arXiv2017

Topological solitons in the supersymmetric Skyrme model

A supersymmetric extension of the Skyrme model was obtained recently, which consists of only the Skyrme term in the Nambu-Goldstone (pion) sector complemented by the same number of quasi-Nambu-Goldstone bosons. Scherk-Schwarz dimensional reduction yields a kinetic term in three or lower dimensions and a potential term in two dimensions, preserving supersymmetry. Euclidean solitons (instantons) are constructed in the supersymmetric Skyrme model. In four dimensions, the soliton is an instanton first found by Speight. Scherk-Schwarz dimensional reduction is then performed once to get a 3-dimensional theory in which a 3d Skyrmion-instanton is found and then once more to get a 2d theory in which a 2d vortex-instanton is obtained. Although the last one is a global vortex it has finite action in contrast to conventional theory. All of them are non-BPS states breaking all supersymmetries.

hep-th↗

arXiv2016

$^3P_2$ Superfluids Are Topological

We clarify topology of $^3P_2$ superfluids which are expected to be realized in the inner cores of neutron stars and cubic odd-parity superconductors. $^3P_2$ phases include uniaxial/biaxial nematic phases and nonunitary ferromagnetic and cyclic phases. We here show that all the phases are accompanied by different types of topologically protected gapless fermions: Surface Majorana fermions in nematic phases and a quartet of (single) itinerant Majorana fermions in the cyclic (ferromagnetic) phase. Using the superfluid Fermi liquid theory, we also demonstrate that dihedral-two and -four biaxial nematic phases are thermodynamically favored in the weak coupling limit under a magnetic field. It is shown that the tricritical point exists on the phase boundary between these two phases and may be realized in the core of realistic magnetars. We unveil the intertwining of symmetry and topology behind mass acquisition of surface Majorana fermions in nematic phases.

cond-mat.supr-con↗

arXiv2016

Field theoretical model of multi-layered Josephson junction and dynamics of Josephson vortices

Multi-layered Josephson junctions are modeled in the context of a field theory, and dynamics of Josephson vortices trapped inside insulators are studied. Starting from a theory consisting of complex and real scalar fields coupled to a U(1) gauge field which admit parallel $N-1$ domain-wall solutions, Josephson couplings are introduced weakly between the complex scalar fields. The $N-1$ domain walls behave as insulators separating $N$ superconductors, where one of the complex scalar fields has a gap. We construct the effective Lagrangian on the domain walls, which reduces to a coupled sine-Gordon model for well-separated walls We then construct sine-Gordon solitons emerging in an effective theory in which we identify Josephson vortices carrying singly quantized magnetic fluxes. When two neighboring superconductors tend to have the same phase, the ground state does not change with the positions of domain walls. On the other hand, when two neighboring superconductors tend to have $π$-phase differences, the ground state has a phase transition depending on the positions of domain walls; when the two walls are close to each other, frustration occurs because of the coupling between the two superconductors besides the thin superconductor. Focusing on the case of three superconductors separated by two insulators, we find for the former case that the interaction between two Josephson vortices on different insulators changes its nature, i.e., attractive or repulsive, depending on the positions of the domain walls. In the latter case, there emerges fractional Josephson vortices when two degenerate ground states appear due to spontaneous charge-symmetry breaking, and the number of the Josephson vortices varies with the position of the domain walls. Our predictions should be verified in multilayered Josephson junctions.

cond-mat.supr-con↗

arXiv2016

Modifying the pion mass in the loosely bound Skyrme model

We study the loosely bound Skyrme model with the addition of two different pion mass terms; this is the most general potential of polynomial form up to second order in the trace of the Skyrme field. The two pion mass terms are called the standard pion mass term and the modified pion mass term. We find that the binding energies are not reduced by the introduction of the modified pion mass, but it is analogous to the standard pion mass term with a decrease in the value of the mass parameter of the loosely bound potential (for large values of the latter parameter). We find by increasing the overall pion mass that we can reduce the classical binding energy of the 4-Skyrmion to the 2.7% level and the total binding energy including the contribution from spin/isospin quantization is reduced to the 5.8% level.

hep-ph↗

arXiv2016

Black hole Skyrmion in a generalized Skyrme model

We study a Skyrme-like model with the Skyrme term and a sixth-order derivative term as higher-order terms, coupled to gravity and we construct Schwarzschild black hole Skyrme hair. We find, surprisingly, that the sixth-order derivative term alone cannot stabilize the black hole hair solutions; the Skyrme term with a large enough coefficient is a necessity.

hep-th↗

arXiv2016

Head butting sheep: Kink Collisions in the Presence of False Vacua

We investigate numerically kink collisions in a $1+1$ dimensional scalar field theory with multiple vacua. The domain wall model we are interested in involves two scalar fields and a potential term built from an asymmetric double well and (double) sine-Gordon potential together with an interaction term. Depending on the initial kink setup and impact velocities, the model allows for a wide range of scattering behaviours. Kinks can repel each other, annihilate, form true or false domain walls and reflect off each other.

hep-th↗

arXiv2016

Ghostbusters in higher derivative supersymmetric theories: who is afraid of propagating auxiliary fields?

We present for the first time a ghost-free higher-derivative chiral model with a propagating auxiliary F-term field (highest component of the chiral multiplet). We obtain this model by removing a ghost in a higher derivative chiral model, with Higgsing it in terms of an auxiliary vector superfield. Depending on the sign of the quadratic derivative term of the chiral superfield, the model contains two ghost free branches of the parameter regions. We find that supersymmetry is spontaneously broken in one branch while it is preserved in the other branch. As a consequence of dynamical F-term field, a conserved U(1) charge corresponding to the number density of $F$ appears, which can be regarded as a generalization of the R-symmetry.

hep-th↗

arXiv2016

Stabilizing semilocal strings by polarization

Semilocal strings are vortices in the extended Abelian-Higgs model with two complex Higgs scalar fields among which a global $SU(2)$ symmetry acts. They are known to be stable (unstable against expansion) in type-I (II) superconductors, in which gauge field is heavier (lighter) than the Higgs scalar field. In this paper, we find that vortices can be stabilized in the whole parameter region including the type-II region by adding a potential term breaking the $SU(2)$ symmetry. We construct numerical solutions in various parameters and determine the vortex phase diagram consisting of six phases. In two phases, a vortex is polarized, that is, split into two half-quantized vortices with a certain distance, to form a vortex molecule, while in the rests a vortex is identical to the conventional Abrikosov-Nielsen-Olesen vortex.

hep-th↗

arXiv2016

Non-perturbative Contributions from Complexified Solutions in $\mathbb{C}P^{N-1}$ Models

We discuss the non-perturbative contributions from real and complex saddle point solutions in the $\mathbb{C}P^1$ quantum mechanics with fermionic degrees of freedom, using the Lefschetz thimble formalism beyond the gaussian approximation. We find bion solutions, which correspond to (complexified) instanton-antiinstanton configurations stabilized in the presence of the fermionic degrees of freedom. By computing the one-loop determinants in the bion backgrounds, we obtain the leading order contributions from both the real and complex bion solutions. To incorporate quasi zero modes which become nearly massless in a weak coupling limit, we regard the bion solutions as well-separated instanton-antiinstanton configurations and calculate a complexified quasi moduli integral based on the Lefschetz thimble formalism. The non-perturbative contributions from the real and complex bions are shown to cancel out in the supersymmetric case and give an (expected) ambiguity in the non-supersymmetric case, which plays a vital role in the resurgent trans-series. For nearly supersymmetric situation, evaluation of the Lefschetz thimble gives results in precise agreement with those of the direct evaluation of the Schrödinger equation. We also perform the same analysis for the sine-Gordon quantum mechanics and point out some important differences showing that the sine-Gordon quantum mechanics does not correctly describe the 1d limit of the $\mathbb{C}P^{N-1}$ field theory of $\mathbb{R} \times S^1$.

hep-th↗

arXiv2016

Skyrmions confined as beads on a vortex ring

A very simple, quadratic potential is used to construct vortex strings in a generalized Skyrme model and an additional quadratic potential is used to embed sine-Gordon-type halfkinks onto the string worldline, yielding half-Skyrmions on a string. The strings are furthermore compactified onto a circle and the halfkinks are forced to appear in pairs; in particular 2B halfkinks (half-Skyrmions) will appear as beads on a ring with B being the number of times the host vortex is twisted and also the baryon number (Skyrmion number) from the bulk point of view. Finally, we construct an effective field theory on the torus, describing the kinks living on the vortex rings.

hep-th↗

arXiv2016

BPS pion domain walls in the supersymmetric chiral Lagrangian

We construct exact solutions of BPS pion domain walls in the four-dimensional $\mathcal{N}=1$ supersymmetric SU(N) chiral Lagrangian with pion masses introduced via linear and quadratic superpotentials. The model admits N discrete vacua in the center of SU(N) for the linear superpotential. In addition to the latter, new vacua appear for the quadratic superpotential. We find that the domain wall solutions of pions (Nambu-Goldstone bosons) that interpolate between a pair of (pion) vacua preserve half of supersymmetry. Contrary to our expectations, we have not been able to find domain walls involving the quasi-Nambu-Goldstone bosons present in the theory, which in turn has the consequence that not all vacua of the theory are connected by a BPS domain wall solution.

hep-th↗

arXiv2016

Non-BPS exact solutions and their relation to bions in ${\mathbb C}P^{N-1}$ models

We investigate non-BPS exact solutions in ${\mathbb C}P^{N-1}$ sigma models on ${\mathbb R}^1 \times S^{1}$ with twisted boundary conditions, by using the Din-Zakrzewski projection method. We focus on the relation of the non-BPS solutions to the ansatz of multi-instanton (bion) configurations and discuss their significance in the context of the resurgence theory. We find that the transition between seemingly distinct configurations of multi-instantons occur as moduli changes in the non-BPS solutions, and the simplest non-BPS exact solution corresponds to multi-bion configurations with fully-compressed double fractional instantons in the middle. It indicates that the non-BPS solutions make small but nonzero contribution to the resurgent trans-series as special cases of the multi-bion configurations. We observe a generic pattern of transitions between distinct multi-bion configurations (flipping partners), leading to the three essential properties of the non-BPS exact solution: (i) opposite sign for terms corresponding to the left and right infinities, (ii) symmetric location of fractional instantons, and (iii) the transition between distinct bion configurations. By studying the balance of forces, we show that the relative phases between the instanton constituents play decisive roles in stability and instability of the muli-instanton configurations. We discuss local and global instabilities of the solutions such as negative modes and the flow to the other saddle points, by considering the deformations of the non-BPS exact solutions within our multi-instanton ansatz. We also briefly discuss some classes of the non-BPS exact solutions in Grassmann sigma models.

hep-th↗

arXiv2016

Aharonov-Bohm Phase in High Density Quark Matter

Stable non-Abelian vortices, which are color magnetic flux tubes as well as superfluid vortices, are present in the color-flavor locked phase of dense quark matter with diquark condensations. We calculate the Aharanov-Bohm phases of charged particles, that is, electrons, muons, and color-flavor locked mesons made of tetraquarks around a non-Abelian vortex.

hep-ph↗

arXiv2016

Semilocal Fractional Instantons

We find semi-local fractional instantons of codimension four in Abelian and non-Abelian gauge theories coupled with scalar fields and the corresponding ${\mathbb C}P^{N-1}$ and Grassmann sigma models at strong gauge coupling. They are 1/4 BPS states in supersymmetric theories with eight supercharges, carry fractional (half) instanton charges characterized by the fourth homotopy group $π_4 (G/H)$, and have divergent energy in infinite spaces. We construct exact solutions for the sigma models and numerical solutions for the gauge theories. Small instanton singularity in sigma models is resolved at finite gauge coupling (for the Abelian gauge theory). Instantons in Abelian and non-Abelian gauge theories have negative and positive instantons charges, respectively, which are related by the Seiberg-like duality that changes the sign of the instanton charge.

hep-th↗