Confinement Phase Research Articles

Hubbard Bands, Mott Transition and Deconfinement in Strongly Correlated Systems

The problem of deconfinement phases in strongly correlated systems is discussed. In space–time dimension d = 3 + 1, a competition of confinement and Coulomb phases occurs, but in d = 2 + 1 the confining phase dominates owing to monopole proliferation, but Dirac points can change the situation. Combining the Kotliar–Ruckenstein representation and fractionalized spin-liquid deconfinement picture, the Mott transition and Hubbard subbands are treated, general expressions in the case of an arbitrary bare band spectrum being obtained. The transition into a metallic state is determined by condensation of a gapless boson mode. The spectrum picture in the insulating state is considerably influenced by the spinon spin-liquid spectrum and hidden Fermi surface.

Holographic model with power-law Maxwell field for color superconductivity

Studying the color superconductivity (CSC) phase is important to understand the physics in the core of the neutron stars which is the only known context where the CSC phase might appear due to the gravitational force squeezing the matter to a sufficiently high density. We propose a simple holographic dual description of the CSC phase transition in the realistic Yang-Mills theory with the power-law Maxwell field. We find the CSC phase transition with the large color number in the deconfinement phase, which is not found in the case of the usual Maxwell field, if the power parameter characterizing for the power-law Maxwell field is sufficiently lower than one but above $1/2$ and the chemical potential is above a critical value. However, the power parameter is not arbitrary below one because when this parameter is sufficiently far away from one it leads to the occurrence of the CSC state in the confinement phase which is not compatible with a nonzero vacuum expectation value of the color nonsinglet operator.

Cosmic strings from pure Yang–Mills theory

We discuss the formation of cosmic strings or macroscopic color flux tubes at the phase transition from the deconfinement to confinement phase in pure Yang--Mills (YM) theory, such as $\mathrm{SU}(N)$, $\mathrm{Sp}(N)$, $\mathrm{SO}(N)$, and $\text{Spin}(N)$, based on the current understanding of theoretical physics. According to the holographic dual descriptions, the cosmic strings are dual to fundamental strings or wrapped D-branes in the gravity side depending on the structure of the gauge group, and the reconnection probability is suppressed by $\mathcal{O}({N}^{\ensuremath{-}2})$ and ${e}^{\ensuremath{-}\mathcal{O}(N)}$, respectively. The pure YM theory thus provides a simple realization of cosmic F- and D-strings without the need for a brane-inflationary scenario or extra dimension. We also review the stability of cosmic strings based on the concept of 1-form symmetry, which further implies the existence of a baryon vertex in some YM theory. We calculate the gravitational wave spectrum that is emitted from the cosmic strings based on an extended velocity-dependent one-scale model and discuss its detectability based on ongoing and planned gravitational-wave experiments. In particular, the SKA and LISA can observe gravitational signals if the confinement scale is higher than $\mathcal{O}({10}^{12})\text{ }\text{ }\mathrm{GeV}$ and $\mathcal{O}({10}^{10})\text{ }\text{ }\mathrm{GeV}$ for $\mathrm{SU}(N)$ with $N=\mathcal{O}(1)$, respectively.

Confinement phase in carbon-nanotubes and the extended massive Schwinger model

Carbon nanotube with electric fluxes confined in one dimension is studied. We show that a Coulomb interaction leads to a confinement phase with many properties similar to QCD in 4D. Low-energy physics is described by the massive Schwinger model with multi-species fermions labeled by the band and valley indices. We propose two means to detect this state. One is through an optical measurement of the exciton spectrum, which has been calculated via the ’t Hooft–Berknoff equation with the light-front field theory. We show that the Gell–Mann−Oakes−Renner relation is satisfied by a dark exciton. The second is the nonlinear transport which is related to Coleman’s ‘half-asymptotic’ state.

Shifting urban mobility patterns due to COVID-19: comparative analysis of implemented urban policies and travel behaviour changes with an assessment of overall GHG emissions implications

COVID-19-induced confinements rapidly change behavioural patterns and social norms of street space use worldwide. In the following study we compile data to assess shifting urban mobility during confinement (phase 1), and in reaction to COVID-19 induced physical distancing policies (phase 2). In a comparative analysis of 16 cities, we show that public transit decreased by 80% during confinement, but individual motorized transport only by 64%. Cycling modal share increased in some cities. COVID-19 and sustainability are intertwined via risks, susceptibility, and positive and negative outcomes, in particular via sustainable development goal 3 (SDG3) (health), SDG5 (gender equality), SDG11 (sustainable cities) and SDG13 (climate action). Confinement-induced social gains are realized in reduced congestion, improved air quality, and less accidents, partially compensated by unhealthy eating, and domestic violence. Our analysis reveals that cities around the world provided more space for cyclist and pedestrians as part of pandemic-related measures, pedestrianizing streets, implementing 550 km ad-hoc bicycle infrastructure and planning additional 1500 km. Our computation indicates that GHG emissions savings due to increased uptake of cycling in the EU reduced urban land transport GHG emissions by 0.3% (1 Mt CO2), while GHG emission savings were larger in cities with pop-up bicycle lanes (between 0.43% and 1.87%). Our findings also demonstrate that proactive cities had already plans in their drawers and demonstrated institutional alignment of vocal civil society, administrations and politicians. We argue that long-term sustainability trajectories of cities will depend on transformation of both physical and digital infrastructures.

Holographic cold dense matter constrained by neutron stars

The equation of state (EOS) for cold dense matter inside neutron stars is investigated by using holographic QCD models that consist of the Einstein-Maxwell-dilaton system and the improved Karch-Katz-Son-Stephanov action for the flavor part. This method of describing holographic nuclear matter in the $\mathrm{Einstein}\text{\ensuremath{-}}\mathrm{Maxwell}\text{\ensuremath{-}}\mathrm{dilaton}+\mathrm{Karch}\text{\ensuremath{-}}\mathrm{Katz}\text{\ensuremath{-}}\mathrm{Son}\text{\ensuremath{-}}\mathrm{Stephanov}$ framework is different from that by using the Dirac-Born-Infeld action and the Chern-Simons terms. Combining with the Hebeler-Lattimer-Pethick-Schwenk intermediate EOS, the hybrid EOS inside the neutron stars is constructed. The obtained hybrid EOS is located in the range that is defined by the low-density chiral effective theory, the high-density perturbative QCD, and the polytropic interpolations between them, and is constrained by the astrophysical observations. The square of the sound velocity reaches a maximum value larger than 0.8 in the region of 2--5 times the saturation baryon number density and approaches the conformal limit at the high baryon density range. The mass-radius relation and the tidal deformability of the neutron stars are in agreement with astrophysical measurements. The possible maximum mass for the neutron star is about $2.5\text{ }\text{ }{M}_{\ensuremath{\bigodot}}$ and the radius is about 12 km then. It is noticed that the holographic quark matter branch in the mass-radius relation is always unstable and the holographic nuclear matter can produce a stable branch. These results indicate that even in the core of the NS, the matter is still in the confinement phase and the quark matter is not favored.

Tunable Confinement-Deconfinement Transition in an Ultracold-Atom Quantum Simulator

The one-dimensional lattice Schwinger model has recently been realized by using bosons in optical lattices. This model contains both confinement and deconfinement phases, the phase diagram of which is controlled by the mass of the matter field and the topological angle. Since varying the mass of the matter field is straightforward experimentally, we propose how to tune the topological angle, allowing exploration of the phase diagram from both directions. We propose that direct experimental evidence of confinement and deconfinement can be obtained by measuring whether a physical charge is localized around a fixed gauge charge to screen it. We also discuss the PXP model realized in the Rydberg-atom array, which is equivalent to the lattice Schwinger model when all local gauge charges are fixed as zero. Although the gauge charges are fixed, we can alternatively probe confinement and deconfinement in the PXP model by studying the relative motion of a pair of a physical charge and an anticharge. Our scheme can be directly implemented in these two relevant experimental platforms of ultracold-atom quantum simulators.Received 15 April 2022Revised 6 June 2022Accepted 26 September 2022DOI:https://doi.org/10.1103/PRXQuantum.3.040317Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasCold gases in optical latticesLattice gauge theoryQuantum simulationSynthetic gauge fieldsAtomic, Molecular & OpticalQuantum InformationCondensed Matter, Materials & Applied PhysicsGeneral PhysicsStatistical PhysicsParticles & Fields

Prefrontal reactivity to TMS perturbation as a toy model of mental health outcomes during the COVID-19 pandemic

Psychosocial hardships associated with the COVID-19 pandemic led many individuals to suffer adverse mental health consequences, however, others show no negative effects. We hypothesized that the electroencephalographic (EEG) response to transcranial magnetic stimulation (TMS) could serve as a toy-model of an individual's capacity to resist psychological stress, in this case linked to the COVID-19 pandemic. We analyzed data from 74 participants who underwent mental health monitoring and concurrent electroencephalography with transcranial magnetic stimulation of the left dorsolateral prefrontal cortex (L-DLPFC) and left inferior parietal lobule (L-IPL). Within the following 19 months, mental health was reassessed at three timepoints during lock-down confinement and different phases of de-escalation in Spain. Compared with participants who remained stable, those who experienced increased mental distress showed, months earlier, significantly larger late EEG responses locally after L-DLPFC stimulation (but not globally nor after L-IPL stimulation). This response, together with years of formal education, was significantly predictive of mental health status during the pandemic. These findings reveal that the effect of TMS perturbation offers a predictive toy model of psychosocial stress response, as exemplified by the COVID-19 pandemic.

Glueballs in a thermal squeezeout model

It has been shown that a first order confinement phase transition can drastically change the relic dark matter abundance in confining dark sectors with only heavy dark quarks. We study the phenomenology of one such model with a Z′ portal to Standard Model. We find that dark glueballs are long-lived in this setup and dilute the dark matter abundance after their decay to Standard Model. With this effect, the correct relic abundance is obtained with dark matter masses up to mathcal{O} (106) TeV. We find that while a part of the parameter space is already ruled out by direct detection and collider searches, there is still a broad space of viable scenarios that can be probed by future experiments.

Living through the COVID-19 pandemic in Mauritius: mental well-being and dependence on Facebook

BackgroundThe unprecedented outbreak of the Coronavirus disease (COVID-19) resulted in numerous psychological consequences among young Mauritians. Prominently, an increase in Facebook usage during the pandemic was observed which could influenced the mental well-being of Facebook users.ObjectiveThe current study sought to explore how the pattern of use, as well as the purpose of Facebook usage, could impact the mental well-being of young Mauritian adults, before, during and after the pandemic-mediated confinement.MethodA cross-sectional approach using a sample of 378 young adults was chosen with a self-administered questionnaire shared through online mediums. The instrument consisted of a combination of validated scales and self-developed items.ResultsThe findings revealed a radical proliferation of social media (91%) through a self-perceived dependency for its informative purpose and related addiction; as well as an evolution of adverse psychological effects characterized by a spectrum of feelings such as restlessness and lowered self-esteem. Higher scores of depressive symptoms were observed during the confinement period (10.05 ± 0.13) as opposed to pre- (0.31 ± 0.79) and post- (0.38 ± 0.09) temporal zones. The lowest scores of mental well-being were noted during the confinement period (0.77 ± 1.8) as compared to pre-confinement (6.56 ± 1.42) and a remarkable recovery was observed post the confinement phase (6.68 ± 1.32). Changes in emotional states were also identified as important predictors of Facebook addiction (χ2(1) = 94.54, p < 0.001) with 48.8% of the variation in the reported addiction behavior matched with 92.6% of perceived addictive characteristics.ConclusionFacebook dependency during the lockdown period was paired with a number of adverse psychological effects among young Mauritians; effects which were likely associated with the frequency and purpose of Facebook use during the pandemic.

Development and simulation of a mathematical model to simulate the phase transmissibility ofCOVID19 in Morocco

In this work we develop a new Reservoir-People (RP) transmission network model to simulate the potential transmission of the COVID-19 virus in the population of Morocco. Our model is original in the sense that it contains parameters that depend on the confinement phases that Morocco has adopted so far. After developing the mathematical model COVID-19-Morocco we define a cost function to minimize with respect to the parameters. We then use genetic algorithms to optimize this functional. The numerical results we obtain confirm that our model is robust and can predict the evolution of the virus in Morocco.

Compact and very high dose-rate plasma focus radiation sources for medical applications

A Dense Plasma Focus (DPF) is a pulsed device able to produce a hot and dense short-lived plasma that could become a fast radiation source for diagnostic applications, external radiotherapy, or intra-operative radiation therapy. The plasma confinement phase, identified as “pinch”, lasts few tens of nanoseconds, during which thermonuclear temperatures and densities could be reached. When the DPF vacuum chamber is filled with gases such as nitrogen, the only significant output are self-collimated charged particle beams (electrons and ions in opposite direction). Using that electron beam, it is possible to devise an ultra-high dose-rate source, with applications for direct irradiation of a tumor bed or for photon conversion after the interaction with a suitable target. The ultra-high dose rate could have potential benefits in mitigating the intrinsic or acquired malignant cell radio-resistance, which can be considered the main obstacle to the long-term survival of a patient, also sparing healthy tissues. This is due as the faster the dose deposition, the more relevant is the radiobiological efficacy (as the tumor cells do not have the time to activate the sub-lethal damage repair mechanisms responsible of the radio-resistance). Due to the novelty of the fast source, the usual models cannot easily describe the biological outcomes, therefore new numerical approaches are needed for predicting the RBE outlined in these regimens.A parametric investigation through the Monte Carlo Damage Simulation Software (MCDS), coupled with the Monte Carlo N-Particle (MCNP) code, has been performed for supporting the experimental results previously obtained by irradiating melanoma cell lines with the Plasma Focus Device for Medical Applications #3 (PFMA-3) as UHDR source and a conventional XRT as standard of comparison.The experimental data were benchmarked with MCNP-MCDS, properly fitting the XRT curves. The validation of the MCDS-MCNP coupling was performed by comparing literature data for conventional XRT, with less than 4% of differences. Next, the experimentally evaluated RBE highlighted that for high doses the RBE calculated on the basis of the surviving fraction (RBE(SF)), is the same of the one from double strand break damages (RBE(DSB)), making coherent the application of the Repair Misrepair Fixation theory (RMF) and providing a basis for a reliable comparison between the two devices. The DPF irradiation outcome has been numerically investigated correlating the experimental experiences with a wide range of code parameter variations to find numerical conditions able to reproduce the data. A recipe based on a combination of more than one SF curves to fit the clonogenic assay in UHDR regimen has also been proposed.The results suggested that the UHDR regimen obtained from the DPF source could change the environmental conditions (e.g., oxygen concentration) while cumulating the dose. This implies that a combination of data and MCDS-MCNP analysis could be applied as a strategy for quantifying biological effects.

Gravitational wave signal from primordial magnetic fields in the Pulsar Timing Array frequency band

The NANOGrav, Parkes, European, and International Pulsar Timing Array (PTA) Collaborations have reported evidence for a common-spectrum process that can potentially correspond to a stochastic gravitational wave background (SGWB) in the 1--100 nHz frequency range. We consider the scenario in which this signal is produced by magnetohydrodynamic (MHD) turbulence in the early Universe, induced by a nonhelical primordial magnetic field at the energy scale corresponding to the quark confinement phase transition. We perform MHD simulations to study the dynamical evolution of the magnetic field and compute the resulting SGWB. We show that the SGWB output from the simulations can be very well approximated by assuming that the magnetic anisotropic stress is constant in time, over a time interval related to the eddy turnover time. The analytical spectrum that we derive under this assumption features a change of slope at a frequency corresponding to the GW source duration that we confirm with the numerical simulations. We compare the SGWB signal with the PTA data to constrain the temperature scale at which the SGWB is sourced, as well as the amplitude and characteristic scale of the initial magnetic field. We find that the generation temperature is constrained to be in the 1--200 MeV range, the magnetic field amplitude must be $>1$\% of the radiation energy density at that time, and the magnetic field characteristic scale is constrained to be $>10$\% of the horizon scale. We show that the turbulent decay of this magnetic field will lead to a field at recombination that can help to alleviate the Hubble tension and can be tested by measurements in the voids of the Large Scale Structure with gamma-ray telescopes like the Cherenkov Telescope Array.

Confinement, mass gap and gauge symmetry in the Yang-Mills theory -- restoration of residual local gauge symmetry --

In this talk we want to discuss the color confinement criterion which guarantees confinement of all colored particles including dynamical quarks and gluons. The most well-known criterion is the Kugo-Ojima color confinement criterion derived in the Lorenz gauge. However, it was pointed out that the Kugo-Ojima criterion breaks down for the Maximal Abelian gauge in which quark confinement has been verified according to the dual superconductivity caused by magnetic monopole condensations. We give the color confinement criterion based on the restoration of the residual local gauge symmetry which can be applied to the Abelian and non-Abelian gauge theories as well irrespective of the compact or non-compact formulation, and enables us to understand confinement in all the cases. Indeed, the restoration of the residual local gauge symmetry which was shown by Hata in the Lorenz gauge to be equivalent to the Kugo-Ojima criterion indeed occurs in the Maximal Abelian gauge for the SU(N) Yang-Mills theory in two-, three- and four-dimensional Euclidean spacetime once the singular topological configurations of gauge fields are taken into account. This result indicates that the color confinement phase is a disordered phase caused by non-trivial topological configurations irrespective of the gauge choice.

Running coupling constant at finite chemical potential and magnetic field from holography * *X.C. is supported by the Research Foundation of Education Bureau of Hunan Province, China (21B0402). L.Z. is supported in part by the Fundamental Research Funds for the Central Universities. D.H. is in part supported by the National Natural Science Foundation of China (11735007, 11890711)

According to gauge/gravity duality, we use an Einstein-Maxwell-dilaton (EMD) model to study the running coupling constant at finite chemical potential and magnetic field. First, we calculate the effect of temperature on the running coupling constant and find the results are qualitatively consistent with lattice guage theory. Subsequently, we calculate the effect of chemical potential and magnetic field on running coupling. It is found that the chemical potential and magnetic field both suppress the running coupling constant. However, the effect of the magnetic field is slightly larger than that of chemical potential for a fixed temperature. Compared with the confinement phase, the magnetic field has a large influence on the running coupling in the deconfinement phase.

Tensor renormalization group study of (3+1)-dimensional ℤ2 gauge-Higgs model at finite density

We investigate the critical endpoints of the (3+1)-dimensional ℤ2 gauge-Higgs model at finite density together with the (2+1)-dimensional one at zero density as a benchmark using the tensor renormalization group method. We focus on the phase transition between the Higgs phase and the confinement phase at finite chemical potential along the critical end line. In the (2+1)-dimensional model, the resulting endpoint is consistent with a recent numerical estimate by the Monte Carlo simulation. In the (3+1)-dimensional case, however, the location of the critical endpoint shows disagreement with the known estimates by the mean-field approximation and the Monte Carlo studies. This is the first application of the tensor renormalization group method to a four-dimensional lattice gauge theory and a key stepping stone toward the future investigation of the phase structure of the finite density QCD.

Color confinement and restoration of residual local gauge symmetries

Abstract All colored particles including dynamical quarks and gluons are confined if the color confinement criterion proposed by Kugo and Ojima is satisfied. The criterion was obtained under a gauge fixing of the Lorenz type. However, it was pointed out that the Kugo–Ojima criterion breaks down for the maximal Abelian gauge, which is quite strange in view of the fact that quark confinement has been verified according to the dual superconductivity caused by magnetic monopole condensations. In order to make a bridge between Kugo–Ojima color confinement and the dual superconductor picture for quark confinement, we investigate a generalization of the color confinement criterion to obtain a unified picture for confinement. We show that the restoration of the residual local gauge symmetry which was shown in the Lorenz gauge by Hata to be equivalent to the Kugo–Ojima criterion indeed occurs in the maximal Abelian gauge for the SU(N) Yang–Mills theory in two-, three-, and four-dimensional Euclidean spacetime once the singular topological configurations of gauge fields are taken into account. This result indicates that the color confinement phase is a disordered phase caused by non-trivial topological configurations irrespective of the gauge choice. As a by-product, we show that the compact U(1) gauge theory can have a disordered confinement phase, while the non-compact U(1) gauge theory has a deconfined Coulomb phase.

Higgs phase as a spin glass phase in D=5 dimensional SU(2) gauge-Higgs theory

According to recent work of Greensite and Matsuyama, the Higgs phase of a gauge Higgs theory is distinguished from the confinement and massless phases by the spontaneous breaking of a global center subgroup of the gauge group, and by confinement type. This is contrary to the notion that there is no essential distinction between the Higgs and confinement phases when the Higgs field is in the fundamental representation of the gauge group. Although this new symmetry breaking order parameter has been investigated in $D=4$ dimensions, there is so far no check in a non-abelian gauge theory containing a massless as well as confinement/Higgs phases, where the prediction is that the symmetry breaking order parameter will show transition lines separating the massless to Higgs and confinement to Higgs phases, but not the massless to confinement phase. In this work we map out the phase structure of the $D=5$ dimensional model, according to both the symmetry breaking parameter and thermodynamic observables, and check the assertion regarding the massless to confinement phase.

Dark matter freeze-out during SU(2)L confinement

We explore the possibility that dark matter is a pair of vector-like fermionic SU(2)L doublets and propose a novel mechanism of dark matter production that proceeds through the confinement of the weak sector of the Standard Model. This confinement phase causes the Standard Model doublets and dark matter to confine into pions. The dark pions freeze-out before the weak sector deconfines and generate a relic abundance of dark matter. We solve the Boltzmann equations for this scenario to determine the scale of confinement and constituent dark matter mass required to produce the observed relic density. We determine which regions of this parameter space evade direct detection, collider bounds, and successfully produce the observed relic density of dark matter. For a TeV scale pair of vector-like fermionic SU(2)L doublets, we find the weak confinement scale to be ∼ 700 TeV.

Symmetry, Confinement, and the Higgs Phase

We show that the Higgs and confinement phases of a gauge Higgs theory, with the Higgs field in the fundamental representation of the gauge group, are distinguished both by a broken or unbroken realization of the global center subgroup of the gauge group, and by the type of confinement in each phase. This is color confinement in the Higgs phase, and a stronger property, which we call “separation-of-charge” confinement, in the confining phase.