Showing papers by "Rong-Gen Cai published in 2015"
TL;DR: In this article, a class of charged black hole solutions in an (n + 2)-dimensional massive gravity with a negative cosmological constant was presented, and the authors studied thermodynamics and phase structure of the black hole solution both in grand canonical ensemble and canonical ensemble.
Abstract: We present a class of charged black hole solutions in an (n + 2)-dimensional massive gravity with a negative cosmological constant, and study thermodynamics and phase structure of the black hole solutions both in grand canonical ensemble and canonical ensemble. The black hole horizon can have a positive, zero or negative constant curvature characterized by constant k. By using Hamiltonian approach, we obtain conserved charges of the solutions and nd black hole entropy still obeys the area formula and the gravitational eld equation at the black hole horizon can be cast into the rst law form of black hole thermodynamics. In grand canonical ensemble, we nd that thermodynamics and phase structure depends on the combination k 2 =4 +c2m 2 in the four dimensional case, where is the chemical potential and c2m 2 is the coecient of the second term in the potential associated with graviton mass. When it is positive, the Hawking-Page phase transition can happen, while as it is negative, the black hole is always thermodynamically stable with a positive capacity. In canonical ensemble, the combination turns out to be k +c2m 2 in the four di
271 citations
TL;DR: A quick and introductory overview of some holographic superconductor models with s-wave, p-wave and d-wave orders can be found in this paper, where the competition and coexistence of these superconductivity orders are studied.
Abstract: In the last years it has been shown that some properties of strongly coupled superconductors can be potentially described by classical general relativity living in one higher dimension, which is known as holographic superconductors This paper gives a quick and introductory overview of some holographic superconductor models with s-wave, p-wave and d-wave orders in the literature from point of view of bottom-up, and summarizes some basic properties of these holographic models in various regimes The competition and coexistence of these superconductivity orders are also studied in these superconductor models
231 citations
TL;DR: In this article, the authors study the thermodynamics and thermodynamic geometry of a Reissner-Nordstr\"om-AdS black hole in the extended phase space by treating the cosmological constant as being related to the number of colors in the boundary gauge theory and its conjugate quantity as the associated chemical potential.
Abstract: We study the thermodynamics and thermodynamic geometry of a five-dimensional Reissner-Nordstr\"om-AdS black hole in the extended phase space by treating the cosmological constant as being related to the number of colors in the boundary gauge theory and its conjugate quantity as the associated chemical potential We find that the contribution of the charge of the black hole to the chemical potential is always positive, and the existence of charge makes the chemical potential become positive more easily We calculate the scalar curvatures of the thermodynamical Weinhold metric, Ruppeiner metric, and Quevedo metric, respectively, in the fixed ${N}^{2}$ case and the fixed $q$ case We find that in the fixed ${N}^{2}$ case, the divergence of the scalar curvature is related to the divergence of the specific heat with fixed electric potential in the Weinhold metric and Ruppeiner metric, and the divergence of the scalar curvature in the Quevedo metric corresponds to the divergence of the specific heat with fixed electric charge density In the fixed $q$ case, however, the divergence of the scalar curvature is related to the divergence of the specific heat with fixed chemical potential in the Weinhold metric and Ruppeiner metric, while in the Quevedo metric, the divergence of the scalar curvature corresponds to the divergence of the specific heat with a fixed number of colors and the vanishing of the specific heat with a fixed chemical potential
163 citations
TL;DR: In this paper, the authors studied the thermodynamics and thermodynamic geometry of a five-dimensional Schwarzschild AdS black hole in AdS 5 × S 5 spacetime by treating the cosmological constant as the number of colors in the boundary gauge theory and its conjugate quantity as the associated chemical potential.
Abstract: We study the thermodynamics and thermodynamic geometry of a five-dimensional Schwarzschild AdS black hole in AdS
5 × S
5 spacetime by treating the cosmological constant as the number of colors in the boundary gauge theory and its conjugate quantity as the associated chemical potential. It is found that the chemical potential is always negative in the stable branch of black hole thermodynamics and it has a chance to be positive, but appears in the unstable branch. We calculate the scalar curvatures of the thermodynamical Weinhold metric, Ruppeiner metric and Quevedo metric, respectively and we find that the scalar curvature in the Weinhold metric is always vanishing, while in the Ruppeiner metric the divergence of the scalar curvature is related to the divergence of the heat capacity with fixed chemical potential, and in the Quevedo metric the divergence of the scalar curvature is related to the divergence of the heat capacity with fixed number of colors and to the vanishing of the heat capacity with fixed chemical potential.
136 citations
TL;DR: In this paper, a nonparametric approach was proposed to reconstruct the interaction between dark energy and dark matter directly from SNIa Union 2.1 data using Gaussian processes, which is a fully Bayesian approach for smoothing data.
Abstract: We present a nonparametric approach to reconstruct the interaction between dark energy and dark matter directly from SNIa Union 2.1 data using Gaussian processes, which is a fully Bayesian approach for smoothing data. In this method, once the equation of state ($w$) of dark energy is specified, the interaction can be reconstructed as a function of redshift. For the decaying vacuum energy case with $w=\ensuremath{-}1$, the reconstructed interaction is consistent with the standard $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ model, namely, there is no evidence for the interaction. This also holds for the constant $w$ cases from $\ensuremath{-}0.9$ to $\ensuremath{-}1.1$ and for the Chevallier-Polarski-Linder (CPL) parametrization case. If the equation of state deviates obviously from $\ensuremath{-}1$, the reconstructed interaction exists at 95% confidence level. This shows the degeneracy between the interaction and the equation of state of dark energy when they get constraints from the observational data.
129 citations
TL;DR: In this article, the influence of the reheating process on the Nreh-wreh plane was investigated and it was shown that for Higgs inflation with a nonminimal coupling to gravity, the predictions are insensitive to reheating phase for current CMB measurements.
Abstract: We investigate the influence on the inflationary predictions from the reheating processes characterized by the e-folding number Nreh and the effective equation-of-state parameter wreh during the reheating phase. For the first time, reheating processes can be constrained in the Nreh-wreh plane from Planck 2015. We find that for Higgs inflation with a nonminimal coupling to gravity, the predictions are insensitive to the reheating phase for current CMB measurements. We also find that the spontaneously broken SUSY inflation and axion monodromy inflation with ϕ2/3 potential, which with instantaneous reheating lie outside or at the edge of the 95% confidence region in the ns-r plane from Planck 2015 TT, TE, EE+lowP, can well fit the data with the help of reheating processes. Future CMB experiments would put strong constraints on reheating processes.
66 citations
TL;DR: In this paper, the authors investigated the behavior of the entanglement entropy of dual field theory in a holographic p-wave model and observed the second order, first order and zeroth order phase transitions.
53 citations
TL;DR: In this paper, a quick and introductory overview of some holographic superconductor models with s-wave, p-wave and d-wave orders in the literature from point of view of bottom-up, summarizes some basic properties of these holographic models in various regimes.
Abstract: In the last years it has been shown that some properties of strongly coupled superconductors can be potentially described by classical general relativity living in one higher dimension, which is known as holographic superconductors. This paper gives a quick and introductory overview of some holographic superconductor models with s-wave, p-wave and d-wave orders in the literature from point of view of bottom-up, and summarizes some basic properties of these holographic models in various regimes. The competition and coexistence of these superconductivity orders are also studied in these superconductor models.
50 citations
TL;DR: In this article, the coexistence and competition of ferromagnetism and superconductivity was investigated in a holographic p-wave superconductor model and a HFR model.
Abstract: By combining a holographic p -wave superconductor model and a holographic ferromagnetism model, we study the coexistence and competition of ferromagnetism and p -wave superconductivity. It is found that the results depend on the self-interaction of magnetic moment of the complex vector field and which phase appears first. In the case where the ferromagnetic phase appears first, if the interaction is attractive, the system shows the ferromagnetism and superconductivity can coexist at low temperatures. If the interaction is repulsive, the system will only be in a pure ferromagnetic state. In the case where the superconducting phase appears first, the attractive interaction will lead to a magnetic p -wave superconducting phase at low temperatures. If the interaction is repulsive, the system will be in a pure p -wave superconducting phase or a ferromagnetic phase when the temperature is lowered.
33 citations
TL;DR: In this paper, Nie et al. presented a holographic s-p superconductor model with a scalar triplet charged under an SU(2) gauge field in the bulk.
Abstract: In a previous paper (Nie et al. in JHEP 1311:087, arXiv:1309.2204 [hep-th], 2013), we presented a holographic s [Formula: see text] p superconductor model with a scalar triplet charged under an SU(2) gauge field in the bulk. We also study the competition and coexistence of the s-wave and p-wave orders in the probe limit. In this work we continue to study the model by considering the full back-reaction. The model shows a rich phase structure and various condensate behaviors such as the "n-type" and "u-type" ones, which are also known as reentrant phase transitions in condensed matter physics. The phase transitions to the p-wave phase or s [Formula: see text] p coexisting phase become first order in strong back-reaction cases. In these first order phase transitions, the free energy curve always forms a swallow tail shape, in which the unstable s [Formula: see text] p solution can also play an important role. The phase diagrams of this model are given in terms of the dimension of the scalar order and the temperature in the cases of eight different values of the back-reaction parameter, which show that the region for the s [Formula: see text] p coexisting phase is enlarged with a small or medium back-reaction parameter but is reduced in the strong back-reaction cases.
32 citations
TL;DR: In this article, a holographic model of paramagnetism/antiferromagnetic phase transition is proposed, which is realized by introducing two real antisymmetric tensor fields coupling to the background gauge field strength and interacting with each other in a dyonic black brane background.
Abstract: In this paper we build a holographic model of paramagnetism/antiferromagnetism phase transition, which is realized by introducing two real antisymmetric tensor fields coupling to the background gauge field strength and interacting with each other in a dyonic black brane background. In the case without an external magnetic field and in low temperatures, the magnetic moments condense spontaneously in an antiparallel manner with the same magnitude and the time reversal symmetry is also broken spontaneously (if the boundary spatial dimension is more than 2, spatial rotational symmetry is broken spontaneously as well), which leads to an antiferromagnetic phase. In the case with the weak external magnetic field, the magnetic susceptibility density has a peak at the critical temperature and satisfies the Curie-Weiss law in the paramagnetic phase of antiferromagnetism. In the strong external magnetic field case, there is a critical magnetic field ${B}_{c}$ in the antiferromagnetic phase: when the magnetic field reaches ${B}_{c}$, the system will return into the paramagnetic phase by a second order phase transition.
TL;DR: In this article, the authors focus on the next ground-based detectors for gravitational wave astronomy, which will be required after the current ground based detectors have completed their initial observations, and probably achieved the first direct detection of gravitational waves.
Abstract: This paper focuses on the next detectors for gravitational wave astronomy which will be required after the current ground based detectors have completed their initial observations, and probably achieved the first direct detection of gravitational waves. The next detectors will need to have greater sensitivity, while also enabling the world array of detectors to have improved angular resolution to allow localisation of signal sources. Sect. 1 of this paper begins by reviewing proposals for the next ground based detectors, and presents an analysis of the sensitivity of an 8 km armlength detector, which is proposed as a safe and cost-effective means to attain a 4-fold improvement in sensitivity. The scientific benefits of creating a pair of such detectors in China and Australia is emphasised. Sect. 2 of this paper discusses the high performance suspension systems for test masses that will be an essential component for future detectors, while sect. 3 discusses solutions to the problem of Newtonian noise which arise from fluctuations in gravity gradient forces acting on test masses. Such gravitational perturbations cannot be shielded, and set limits to low frequency sensitivity unless measured and suppressed. Sects. 4 and 5 address critical operational technologies that will be ongoing issues in future detectors. Sect. 4 addresses the design of thermal compensation systems needed in all high optical power interferometers operating at room temperature. Parametric instability control is addressed in sect. 5. Only recently proven to occur in Advanced LIGO, parametric instability phenomenon brings both risks and opportunities for future detectors. The path to future enhancements of detectors will come from quantum measurement technologies. Sect. 6 focuses on the use of optomechanical devices for obtaining enhanced sensitivity, while sect. 7 reviews a range of quantum measurement options.
TL;DR: In this paper, a gravity dual for the insulator/metal phase transition and colossal magnetoresistance effect found in some manganese oxides materials was constructed within massive gravity, and the relation with the electronic phase separation was discussed.
Abstract: Within massive gravity, we construct a gravity dual for the insulator/metal phase transition and colossal magnetoresistance effect found in some manganese oxides materials. In the heavy graviton limit, a remarkable magnetic-field-sensitive DC resistivity peak appears at the Curie temperature, where an insulator/metal phase transition happens and the magnetoresistance is scaled with the square of field-induced magnetization. We find that metallic and insulating phases coexist below the Curie point and the relation with the electronic phase separation is discussed.
TL;DR: A modified Lagrangian density for the anti-symmetric tensor, which is ghost free and causality is well-defined, and keeps all the significant results in the original model qualitatively, was presented in this article.
Abstract: A real anti-symmetric tensor field was introduced to realize a holographic magnetic ordered phase in our previous works. However, a more careful analysis shows there is a vector ghost in the model. In this paper we present a modified Lagrangian density for the anti-symmetric tensor, which is ghost free and causality is well-defined, and keeps all the significant results in the original model qualitatively. We show this modified Lagrangian density could come from the dimensional compactification of $p$-form field in String/M-theory. For static curved space-time, we also prove that this modified model is ghost free and dose not violate causality. This new model offers a solid foundation for the application of antisymmetric tensor field in holographic duality, especially for the spontaneous magnetization.
TL;DR: In this article, a massive 2-form field coupled to the Maxwell field strength in the bulk was introduced to investigate the holographic ferromagnetic phase transition in an AdS4 black brane background.
Abstract: In this paper we investigate in some detail the holographic ferromagnetic phase transition in an AdS4 black brane background by introducing a massive 2-form field coupled to the Maxwell field strength in the bulk. In two probe limits, one is to neglect the back reaction of the 2-form field to the background geometry and to the Maxwell field, and the other to neglect the back reaction of both the Maxwell field and the 2-form field, we find that the spontaneous magnetization and the ferromagnetic phase transition always happen when the temperature gets low enough with similar critical behavior. We calculate the DC resistivity in a semi-analytical method in the second probe limit and find it behaves as the colossal magnetic resistance effect in some materials. In the case with the first probe limit, we obtain the off-shell free energy of the holographic model near the critical temperature and compare with the Ising-like model. We also study the back reaction effect and find that the phase transition is always second order. In addition, we find an analytical Reissner-Norstrom-like black brane solution in the Einstein-Maxwell-2-form field theory with a negative cosmological constant.
TL;DR: In this article, a gravity dual of antiferromagnetic quantum phase transition induced by magnetic field was proposed and the critical behavior around the quantum critical point was studied, showing that the boundary critical theory is a strong coupling theory with dynamic exponent z ¼ 2 and that the hyperscaling law is violated.
Abstract: We propose a gravity dual of antiferromagnetic quantum phase transition induced by magnetic field and study the critical behavior around the quantum critical point. It turns out that the boundary critical theory is a strong coupling theory with dynamic exponent z ¼ 2 and that the hyperscaling law is violated and
logarithmic corrections appear near the quantum critical point. Some novel scaling relations are predicated, which can be tested by experiment data in the future. We also make some comparison with experimental
data on low-dimensional magnets BiCoPO5 and pyrochlores Er2−2xY2xTi2O7.
TL;DR: In this paper, a Gauss-Bonnet braneworld model was proposed to solve both the unitarity and stability problems which usually plague Higgs inflation, where the Higgs boson can be the inflaton with the help of a large nonminimal coupling to curvature in four dimensions.
Abstract: The measured masses of the Higgs boson and top quark indicate that the effective potential of the standard model either develops an unstable electroweak vacuum or stands stable all the way up to the Planck scale. In the latter case in which the top quark mass is about $2\ensuremath{\sigma}$ below its present central value, the Higgs boson can be the inflaton with the help of a large nonminimal coupling to curvature in four dimensions. We propose a scenario in which the Higgs boson can be the inflaton in a five-dimensional Gauss-Bonnet braneworld model to solve both the unitarity and stability problems which usually plague Higgs inflation. We find that in order for Higgs inflation to happen successfully in the Gauss-Bonnet regime, the extra dimension scale must appear roughly in the range between the TeV scale and the instability scale of standard model. At the tree level, our model can give rise to a naturally small nonminimal coupling $\ensuremath{\xi}\ensuremath{\sim}\mathcal{O}(1)$ for the Higgs quartic coupling $\ensuremath{\lambda}\ensuremath{\sim}\mathcal{O}(0.1)$ if the extra dimension scale lies at the TeV scale. At the loop level, the inflationary predictions at the tree level are preserved. Our model can be confronted with future experiments and observations from both particle physics and cosmology.
TL;DR: In this article, the transfer-of-copyright-agreement for terms and conditions regarding re-use of this article is discussed. But the authors do not specify the terms of their agreement.
Abstract: This published version of this paper is available online at: http://dx.doi.org/10.1103/PhysRevD.92.046005. Please see http://journals.aps.org/authors/transfer-of-copyright-agreement for terms and conditions regarding re-use of this article.
TL;DR: In this paper, a model-independent principal component method for the reionization history is applied to give constraints on the cosmological parameters from recent Planck 2015 data, and it is shown that the universe are not completely reionized at redshifts $z \ge 8.5$ at 95% CL.
Abstract: The simple assumption of an instantaneous reionization of the Universe may bias estimates of cosmological parameters. In this paper a model-independent principal component method for the reionization history is applied to give constraints on the cosmological parameters from recent Planck 2015 data. We find that the Universe are not completely reionized at redshifts $z \ge 8.5$ at 95% CL. Both the reionization optical depth and the matter fluctuation amplitude are higher than but consistent with those obtained in the standard instantaneous reionization scheme. The high estimated value of the matter fluctuation amplitude strengthens the tension between Planck CMB observations and some astrophysical data, such as cluster counts and weak lensing. The tension can significantly be relieved if the neutrino masses are allowed to vary. Thanks to a high scalar spectral index, the low-scale spontaneously broken SUSY inflationary model can fit the data well, which is marginally disfavored at 95% CL in the Planck analysis.
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TL;DR: In this article, a massive 2-form field coupled to the Maxwell field strength in the bulk was introduced to investigate the holographic ferromagnetic phase transition in an AdS${_4}$ black brane background.
Abstract: In this paper, we investigate in some detail the holographic ferromagnetic phase transition in an AdS${_4}$ black brane background by introducing a massive 2-form field coupled to the Maxwell field strength in the bulk. In the two probe limits, one is to neglect the back reaction of the 2-form field to the background geometry and to the Maxwell field, and the other to neglect the back reaction of both the Maxwell field and the 2-form field, we find that the spontaneous magnetization and the ferromagnetic phase transition always happen when the temperature gets low enough with similar critical behavior. We calculate the DC resistivity in a semi-analytical method in the second probe limit and find it behaves as the colossal magnetic resistance effect in some materials. In the case with the first probe limit, we obtain the off-shell free energy of the holographic model near the critical temperature and compare with the Ising-like model. We also study the back reaction effect and find that the phase transition is always second order. In addition, we find an analytical Reissner-Norstrom-like black brane solution in the Einstein-Maxwell-2-form field theory with a negative cosmological constant.
TL;DR: In this paper, the authors investigated the effect of the self-interaction term on the critical amplitudes, forming time of apparent horizon, stable island and energy transformation of a massless scalar field.
Abstract: The gravitational collapse of a massless scalar field with a self-interaction term $\lambda\phi^4$ in anti-de Sitter space is investigated. We numerically investigate the effect of the self-interaction term on the critical amplitudes, forming time of apparent horizon, stable island and energy transformation. The results show that a positive $\lambda$ suppresses the formation of black hole, while a negative $\lambda$ enhances the process. We define two susceptibilities to characterize the effect of the self-interaction on the black hole formation, and find that near the critical amplitude, there exists a universal scaling relation with the critical exponent $\alpha \approx 0.74$ for the time of black hole formation.