This is a writeup of lectures delivered at the Asian Pacific Introductory School on Superstring and Related Topics in Beijing(2006)and an expanded version of these lectures given at the Third Summer School on Strings,...This is a writeup of lectures delivered at the Asian Pacific Introductory School on Superstring and Related Topics in Beijing(2006)and an expanded version of these lectures given at the Third Summer School on Strings,Fields and Holography in Nanjing(2023).It aims to provide both a historical and pedagogical account of developments in finding 1/2 Bogomol?nyi–Prasad–Sommerfield(BPS)extended string solitons during the early stage of the so-called second string revolution,before which these objects were thought to be unrelated to strings.Nonsupersymmetric solutions related to brane/anti brane systems or non-BPS systems are also discussed.展开更多
We investigate the statistical nature of holographic gas, which may represent the quasi-particle excitations of a strongly correlated gravitational system. We find that the holographic entropy can be obtained by modif...We investigate the statistical nature of holographic gas, which may represent the quasi-particle excitations of a strongly correlated gravitational system. We find that the holographic entropy can be obtained by modifying degeneracy. We calculate thermodynamical quantities and investigate stability of the holographic gas. When applying to cosmology, we find that the holographic gas behaves as holographic dark energy, and the parameter c in holographic dark energy can be calculated from our model. Our model of holographic gas generally predicts c 〈 1, implying that the fate of our universe is phantom-like.展开更多
This is a follow of previous work entitled "One Electron Atom in Special Relativity with de Sitter SpaceTime Symmetry" [Commun. Theor. Phys. 57(2012) 930]. In this paper, we consider the higher order calcula...This is a follow of previous work entitled "One Electron Atom in Special Relativity with de Sitter SpaceTime Symmetry" [Commun. Theor. Phys. 57(2012) 930]. In this paper, we consider the higher order calculations and contributions in the previous framework to solve one electron atoms in de Sitter invariant relativistic quantum mechanics. The next-to-leading-order calculations in 1/R2-expansions show that the fine-structure constant α is variant with cosmologic time going by in the de Sitter invariant special relativistic quantum mechanics with standard FRW cosmologic model.展开更多
Recently,a novel bootstrap method for numerical calculations in matrix models and quantum mechanical systems was proposed.We apply the method to certain quantum mechanical systems derived from some well-known local to...Recently,a novel bootstrap method for numerical calculations in matrix models and quantum mechanical systems was proposed.We apply the method to certain quantum mechanical systems derived from some well-known local toric Calabi-Yau geometries,where the exact quantization conditions have been conjecturally related to topological string theory.We find that the bootstrap method provides a promising alternative for the precision numerical calculations of the energy eigenvalues.An improvement in our approach is to use a larger set of two-dimensional operators instead of one-dimensional ones.We also apply our improved bootstrap methods to some non-relativistic models in the recent literature and demonstrate better numerical accuracies.展开更多
The de Sitter invariant Special Relativity （dS-SR） is SR with constant curvature, and a natural extension of usual Einstein SR （E-SR）. In this paper, we solve the dS-SR Dirac equation of Hydrogen by means of the a...The de Sitter invariant Special Relativity （dS-SR） is SR with constant curvature, and a natural extension of usual Einstein SR （E-SR）. In this paper, we solve the dS-SR Dirac equation of Hydrogen by means of the adiabatic approach and the quasi-stationary perturbation calculations of QM. Hydrogen atom is located in the light cone of the Universe. FRW metric and ACDM cosmological model are used to discuss this issue. To the atom, effects of de Sitter space-time geometry described by Beltrami metric are taken into account. The dS-SR Dirac equation turns out to be a time dependent quantum Hamiltonian system. We reveal that： （i） The fundamental physics constants me, h, e variate adiabatically along with cosmologic time in dS-SR QM framework. But the fine-structure constant α≡ - e^2/（hc） keeps to be invariant; （ii） （2s^1/2 - 2p^1/2）-splitting due to dS-SR QM effects： By means of perturbation theory, that splitting △E（z） are calculated analytically, which belongs to O（1/R^2）-physics of dS-SR QM. Numerically, we find that when ｜R｜ = {103 Gly, 104 Gly, 105 Gly}, and z = {1, or 2}, the AE（z） 〉〉 1 （Lamb shift）. This indicates that for these cases the hyperfine structure effects due to QED could be ignored, and the dS-SR fine structure effects are dominant. This effect could be used to determine the universal constant R in dS-SR, and be thought as a new physics beyond E-SR.展开更多
Based on the Wigner function in local equilibrium, we derive hydrodynamical quantities for a system of polarized spin-1/2 particles: the particle number current density, the energy-momentum tensor, the spin tensor, an...Based on the Wigner function in local equilibrium, we derive hydrodynamical quantities for a system of polarized spin-1/2 particles: the particle number current density, the energy-momentum tensor, the spin tensor, and the dipole moment tensor. Compared with ideal hydrodynamics without spin, additional terms at the first and second orders in the Knudsen number Κ_(n) and the average spin polarization Χ_(s) have been derived. The Wigner function can be expressed in terms of matrix-valued distributions, whose equilibrium forms are characterized by thermodynamical parameters in quantum statistics. The equations of motion for these parameters are derived by conservation laws at the leading and next-to-leading order Κ_(n) and Χ_(s).展开更多
The unsteady magnetohydrodynamic flow of an electrically conducting viscous incompressible third grade fluid bounded by an infinite porous plate is studied with the Hall effect. An external uniform magnetic field is a...The unsteady magnetohydrodynamic flow of an electrically conducting viscous incompressible third grade fluid bounded by an infinite porous plate is studied with the Hall effect. An external uniform magnetic field is applied perpendicular to the plate and the fluid motion is subjected to a uniform suction and injection. Similarity transformations are employed to reduce the non-linear equations governing the flow under discussion to two ordinary differential equations （with and without dispersion terms）. Using the finite difference scheme, numerical solutions represented by graphs with reference to the various involved parameters of interest are discussed and appropriate conclusions are drawn.展开更多
Influences of topological defect and dislocation on conductivity behavior of charge carriers in external electromagnetic fields are studied. Particularly the quantum Hall effect is investigated in detail. It is found ...Influences of topological defect and dislocation on conductivity behavior of charge carriers in external electromagnetic fields are studied. Particularly the quantum Hall effect is investigated in detail. It is found that the nontrivial deformations of spacetime due to topological defect and dislocation produce an electric current at the leading order of perturbation theory. This current then induces a deformation on the Hall conductivity. The corrections on the Hall conductivity depend on the external electric fields, the size of the sample and the momentum of the particle.展开更多
We generalize the computations of the long-range interactions between two parallel stacks of branes to various cases when two stacks of branes are not placed parallel to each other. We classify the nature of interacti...We generalize the computations of the long-range interactions between two parallel stacks of branes to various cases when two stacks of branes are not placed parallel to each other. We classify the nature of interaction(repulsive or attractive) for each special case and this classification can be used to justify the nature of long-range interaction between two complicated brane systems such as brane bound states. We will provide explicit examples in this paper to demonstrate this.展开更多
We present a detailed study of dynamically generating an M2 brane from super-gravitons(or DO branes)in a pp-wave background possessing maximal spacetime SUSY.We have three kinds of dynamical solutions depending on the...We present a detailed study of dynamically generating an M2 brane from super-gravitons(or DO branes)in a pp-wave background possessing maximal spacetime SUSY.We have three kinds of dynamical solutions depending on the excess energy which appears as an order parameter signalling a critical phenomenon about the solutions.As the excess energy is below a critical value,we have two branches of the solution,one can have its size zero while the other cannot for each given excess energy.However there can be an instanton tunnelling between the two.Once the excess energy is above the critical value,we have a single solution whose dynamical behavior is basically independent of the background chosen and whose size can be zero at some instant.A by product of this study is that the size of particles or extended objects can grow once there is a non-zero excess energy even without the presence of a background flux,therefore lending support to the spacetime uncertainty principle.展开更多
We introduce a new interpretation of chemical potential and show that holographic entropy is entropybound,which is supported by two ideal cases discussed in detail.One is sparse but incompressible liquid like a star o...We introduce a new interpretation of chemical potential and show that holographic entropy is entropybound,which is supported by two ideal cases discussed in detail.One is sparse but incompressible liquid like a star ofuniform density and the other is a screen at infinity in spherically symmetric spacetime.Our work is based on the newscenario of entropy force and holographic thermodynamics,and the Brown-York quasi-local energy.展开更多
Based on the definition of the apparent horizon in a general two-dimensional dilaton gravity theory, we analyze the tunnelling phenomenon near the apparent horizon. In this theory the definition of the horizon is very...Based on the definition of the apparent horizon in a general two-dimensional dilaton gravity theory, we analyze the tunnelling phenomenon near the apparent horizon. In this theory the definition of the horizon is very different from those in higher-dimensional gravity theories. By using the Hamilton-Jacobi method, the spectrum of the radiation is obtained and the temperature of the radiation is read out from this spectrum. The temperature is proportional to the surface gravity of the apparent horizon as usual. Besides, in stationary cases we calculate the spectrum by using Parikh and Wilczek＇s null geodesic method and the result conforms to that obtained by using the Harnilton-Jacobi method. This is expected since the flamilton-Jacobi method applies to generic spacetimes, including stationary ones.展开更多
Riemannian geometry, as a basis for general relativity, can be obtained from the more general Finsler geometry in terms of the Cartan connection and Chern connection, as discussed frequently in the literature. However...Riemannian geometry, as a basis for general relativity, can be obtained from the more general Finsler geometry in terms of the Cartan connection and Chern connection, as discussed frequently in the literature. However, there are other gravity theories that can be made to be equivalent to general relativity but are based on non-Riemannian geometry. Famous examples are the Teleparallel and Symmetric Teleparallel gravity theories. In this paper, we show how to obtain the geometry for Teleparallel gravity from Finsler geometry in terms of a ‘Teleparallel type’ connection.展开更多
The Wilson coefficients of the standard model effective field theory are subject to a series of positivity bounds.It has been shown that while the positivity part of the ultraviolet(UV)partial wave unitarity leads to ...The Wilson coefficients of the standard model effective field theory are subject to a series of positivity bounds.It has been shown that while the positivity part of the ultraviolet(UV)partial wave unitarity leads to the Wilson coefficients living in a convex cone,further including the nonpositivity part caps the cone from above.For Higgs scattering,a capped positivity cone was obtained using a simplified,linear unitarity condition without utilizing the full internal symmetries of Higgs scattering.Here,we further implement stronger nonlinear unitarity conditions from the UV,which generically gives rise to better bounds.We show that,for the Higgs case in particular,while the nonlinear unitarity conditions per se do not enhance the bounds,the fuller use of the internal symmetries do shrink the capped positivity cone significantly.展开更多
We study the cosmology of a quintessence scalar held which is equivalent to a non-barotropic perfect fluid of constant pressure.The coincidence problem is alleviated by such a quintessence equation-of-state that inter...We study the cosmology of a quintessence scalar held which is equivalent to a non-barotropic perfect fluid of constant pressure.The coincidence problem is alleviated by such a quintessence equation-of-state that interpolates between plateau of zero at large redshifts and plateau of minus one as the redshift approaches to zero.The quintessence Geld is neither a unified dark matter nor a mixture of cosmological constant and cold dark matter,relying on the facts that the quintessence density contrasts of sub-horizon modes would undergo a period of late-time dechne and the squared sound speeds of quintessence perturbations do not vanish.What a role does the quintessence play is dynamic dark energy,its clustering could remarkably reduce the growth rate of the density perturbations of non-relativistic matters.展开更多
Ultracompact dark matter minihalos （UCMHs） would be formed during the early universe if there were large density perturbations. If dark matter can decay into particles described by the standard model, such as neutri...Ultracompact dark matter minihalos （UCMHs） would be formed during the early universe if there were large density perturbations. If dark matter can decay into particles described by the standard model, such as neutrinos, these objects would become potential astrophysical sources of emission which could be detected by in- struments such as IceCube. In this paper, we investigate neutrino signals from nearby UCMHs due to gravitino dark matter decay and compare these signals with the back- ground neutrino flux which is mainly from the atmosphere to obtain constraints on the abundance of UCMHs.展开更多
Noncommutative Chern-Simons （NCCS） theory is a workable description for the fractional quantum Hall fluid. We apply and generalize the NCCS theory to the physically important case with an edge. Prom relabeling symme...Noncommutative Chern-Simons （NCCS） theory is a workable description for the fractional quantum Hall fluid. We apply and generalize the NCCS theory to the physically important case with an edge. Prom relabeling symmetry of electrons and incompressibility of the fluid, we obtain a constraint and reduce the two-dimensional NCCS theory to a one-dimensional chiral Tomonaga-Luttinger liquid theory, which contains additional interaction terms. Further, we calculate one-loop corrections to the boson and electron propagators and obtain a new tunneling exponent, which agrees with experiments.展开更多
We propose a new holographic program of gravity in which we introduce a surface stress tensor.Our proposal differs from Verlinde's in several aspects.First,we use an open or a closed screen.Second,the temperature ...We propose a new holographic program of gravity in which we introduce a surface stress tensor.Our proposal differs from Verlinde's in several aspects.First,we use an open or a closed screen.Second,the temperature is not necessary,but a surface energy density and pressure are introduced.The surface stress tensor is proportional to the extrinsic curvature.Third,the energy we use is Brown-York energy and the equipartition theorem is violated by a non-vanishing surface pressure.We discuss holographic thermodynamics of a gas of weak gravity and find a chemical potential,and then show that Verlinde's program does not lead to reasonable thermodynamics.The holographic entropy is similar to the Bekenstein entropy bound.展开更多
I show the formulation of de Sitter Special Relativity （dS-SR） based on Dirac-Lu-Zou-Guo’s discussions. dS-SR quantum mechanics is formulated, and the dS-SR Dirac equation for hydrogen is suggested. The equation in...I show the formulation of de Sitter Special Relativity （dS-SR） based on Dirac-Lu-Zou-Guo’s discussions. dS-SR quantum mechanics is formulated, and the dS-SR Dirac equation for hydrogen is suggested. The equation in the earth-QSO framework reference is solved by means of the adiabatic approach. It’s found that the fine-structure ＂constant＂ α in dS-SR varies with time. By means of the t-z relation of the ΛCDM model, α’s time-dependency becomes redshift z-dependent. The dS-SR’s predictions of △α/α agree with data of spectra of 143 quasar absorption systems, the dS-space-time symmetry is SO（3, 2） （i.e., anti-dS group） and the universal parameter R （de Sitter ratio） in dS-SR is estimated to be R ≈ 2.73×1012 ly. The effects of dS-SR become visible at the cosmic space-time scale （i.e., the distance 109 ly）. At that scale, dS-SR is more reliable than Einstein SR. The α-variation with time is evidence of SR with de Sitter symmetry.展开更多
In the strong uniform magnetic field, the noncommutative plane （NCP） caused by the lowest Landau level （LLL） effect, and QED with NCP （QED-NCP） are studied. Being similar to the condensed matter theory of quantu...In the strong uniform magnetic field, the noncommutative plane （NCP） caused by the lowest Landau level （LLL） effect, and QED with NCP （QED-NCP） are studied. Being similar to the condensed matter theory of quantum Hall effect, an effective filling factor f（B） is introduced to characterize the possibility that the electrons stay on the LLL. The analytic and numerical results of the differential cross section for the process of backward Compton scattering in accelerator with unpolarized or polarized initial photons are calculated. The existing data of BL38B2 in Spring-8 have been analyzed roughly and compared with the numerical predictions primitively. We propose a precise measurement of the differential cross sections of backward Compton scattering in a strong perpendicular magnetic field, which may reveal the effects of NCP.展开更多
基金the support by grants from the NNSF of China with Grant Nos.12275264 and 12247103。
文摘This is a writeup of lectures delivered at the Asian Pacific Introductory School on Superstring and Related Topics in Beijing(2006)and an expanded version of these lectures given at the Third Summer School on Strings,Fields and Holography in Nanjing(2023).It aims to provide both a historical and pedagogical account of developments in finding 1/2 Bogomol?nyi–Prasad–Sommerfield(BPS)extended string solitons during the early stage of the so-called second string revolution,before which these objects were thought to be unrelated to strings.Nonsupersymmetric solutions related to brane/anti brane systems or non-BPS systems are also discussed.
基金supported by National Natural Science Foundation of China under Grant No. 10525050a "973" Project under Grant No. 2007CB815401
文摘We investigate the statistical nature of holographic gas, which may represent the quasi-particle excitations of a strongly correlated gravitational system. We find that the holographic entropy can be obtained by modifying degeneracy. We calculate thermodynamical quantities and investigate stability of the holographic gas. When applying to cosmology, we find that the holographic gas behaves as holographic dark energy, and the parameter c in holographic dark energy can be calculated from our model. Our model of holographic gas generally predicts c 〈 1, implying that the fate of our universe is phantom-like.
基金Supported in part by National Natural Science Foundation of China under Grant No.11375169
文摘This is a follow of previous work entitled "One Electron Atom in Special Relativity with de Sitter SpaceTime Symmetry" [Commun. Theor. Phys. 57(2012) 930]. In this paper, we consider the higher order calculations and contributions in the previous framework to solve one electron atoms in de Sitter invariant relativistic quantum mechanics. The next-to-leading-order calculations in 1/R2-expansions show that the fine-structure constant α is variant with cosmologic time going by in the de Sitter invariant special relativistic quantum mechanics with standard FRW cosmologic model.
基金supported in parts by the National Natural Science Foundation of China(Grants No.11947301 and No.12047502)
文摘Recently,a novel bootstrap method for numerical calculations in matrix models and quantum mechanical systems was proposed.We apply the method to certain quantum mechanical systems derived from some well-known local toric Calabi-Yau geometries,where the exact quantization conditions have been conjecturally related to topological string theory.We find that the bootstrap method provides a promising alternative for the precision numerical calculations of the energy eigenvalues.An improvement in our approach is to use a larger set of two-dimensional operators instead of one-dimensional ones.We also apply our improved bootstrap methods to some non-relativistic models in the recent literature and demonstrate better numerical accuracies.
基金Supported in part by National Natural Science Foundation of China under Grant No. 10975128by the Chinese Science Academy Foundation under Grant No. KJCX-YW-N29
文摘The de Sitter invariant Special Relativity （dS-SR） is SR with constant curvature, and a natural extension of usual Einstein SR （E-SR）. In this paper, we solve the dS-SR Dirac equation of Hydrogen by means of the adiabatic approach and the quasi-stationary perturbation calculations of QM. Hydrogen atom is located in the light cone of the Universe. FRW metric and ACDM cosmological model are used to discuss this issue. To the atom, effects of de Sitter space-time geometry described by Beltrami metric are taken into account. The dS-SR Dirac equation turns out to be a time dependent quantum Hamiltonian system. We reveal that： （i） The fundamental physics constants me, h, e variate adiabatically along with cosmologic time in dS-SR QM framework. But the fine-structure constant α≡ - e^2/（hc） keeps to be invariant; （ii） （2s^1/2 - 2p^1/2）-splitting due to dS-SR QM effects： By means of perturbation theory, that splitting △E（z） are calculated analytically, which belongs to O（1/R^2）-physics of dS-SR QM. Numerically, we find that when ｜R｜ = {103 Gly, 104 Gly, 105 Gly}, and z = {1, or 2}, the AE（z） 〉〉 1 （Lamb shift）. This indicates that for these cases the hyperfine structure effects due to QED could be ignored, and the dS-SR fine structure effects are dominant. This effect could be used to determine the universal constant R in dS-SR, and be thought as a new physics beyond E-SR.
基金Supported by the National Natural Science Foundation of China (Grant Nos. 11890713, 11890710, 11947301, 11935007, 11221504,11861131009, 11890714, 11890710, and 12047528)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No. XDB34030102)。
文摘Based on the Wigner function in local equilibrium, we derive hydrodynamical quantities for a system of polarized spin-1/2 particles: the particle number current density, the energy-momentum tensor, the spin tensor, and the dipole moment tensor. Compared with ideal hydrodynamics without spin, additional terms at the first and second orders in the Knudsen number Κ_(n) and the average spin polarization Χ_(s) have been derived. The Wigner function can be expressed in terms of matrix-valued distributions, whose equilibrium forms are characterized by thermodynamical parameters in quantum statistics. The equations of motion for these parameters are derived by conservation laws at the leading and next-to-leading order Κ_(n) and Χ_(s).
文摘The unsteady magnetohydrodynamic flow of an electrically conducting viscous incompressible third grade fluid bounded by an infinite porous plate is studied with the Hall effect. An external uniform magnetic field is applied perpendicular to the plate and the fluid motion is subjected to a uniform suction and injection. Similarity transformations are employed to reduce the non-linear equations governing the flow under discussion to two ordinary differential equations （with and without dispersion terms）. Using the finite difference scheme, numerical solutions represented by graphs with reference to the various involved parameters of interest are discussed and appropriate conclusions are drawn.
基金Supported by the China Scholarship Council under Grant No 201207010002the Hanjiang Scholar Project of Shaanxi University of Technology+3 种基金the National Natural Science Foundation of China under Grant No 11147181the Scientific Research Project of Shaanxi Province under Grant Nos 2009K01-54 and 12JK0960the Startup Foundation of the University of Science and Technology of Chinathe Project of Knowledge Innovation Program of the Chinese Academy of Sciences
文摘Influences of topological defect and dislocation on conductivity behavior of charge carriers in external electromagnetic fields are studied. Particularly the quantum Hall effect is investigated in detail. It is found that the nontrivial deformations of spacetime due to topological defect and dislocation produce an electric current at the leading order of perturbation theory. This current then induces a deformation on the Hall conductivity. The corrections on the Hall conductivity depend on the external electric fields, the size of the sample and the momentum of the particle.
基金Supported by National Natural Science Foundation of China under Grant No.11235010
文摘We generalize the computations of the long-range interactions between two parallel stacks of branes to various cases when two stacks of branes are not placed parallel to each other. We classify the nature of interaction(repulsive or attractive) for each special case and this classification can be used to justify the nature of long-range interaction between two complicated brane systems such as brane bound states. We will provide explicit examples in this paper to demonstrate this.
基金We acknowledge support by grants from the NSF of China with Grant No:11775212 and 12047502.
文摘We present a detailed study of dynamically generating an M2 brane from super-gravitons(or DO branes)in a pp-wave background possessing maximal spacetime SUSY.We have three kinds of dynamical solutions depending on the excess energy which appears as an order parameter signalling a critical phenomenon about the solutions.As the excess energy is below a critical value,we have two branches of the solution,one can have its size zero while the other cannot for each given excess energy.However there can be an instanton tunnelling between the two.Once the excess energy is above the critical value,we have a single solution whose dynamical behavior is basically independent of the background chosen and whose size can be zero at some instant.A by product of this study is that the size of particles or extended objects can grow once there is a non-zero excess energy even without the presence of a background flux,therefore lending support to the spacetime uncertainty principle.
文摘We introduce a new interpretation of chemical potential and show that holographic entropy is entropybound,which is supported by two ideal cases discussed in detail.One is sparse but incompressible liquid like a star ofuniform density and the other is a screen at infinity in spherically symmetric spacetime.Our work is based on the newscenario of entropy force and holographic thermodynamics,and the Brown-York quasi-local energy.
基金Supported by the National Natural Science Foundation of China under Grant Nos.11622543 and 11235010by the Open Project Program of Key Laboratory of Theoretical Physics,Institute of Theoretical Physics,Chinese Academy of Sciences,China(No.Y5KF161CJ1)
文摘Based on the definition of the apparent horizon in a general two-dimensional dilaton gravity theory, we analyze the tunnelling phenomenon near the apparent horizon. In this theory the definition of the horizon is very different from those in higher-dimensional gravity theories. By using the Hamilton-Jacobi method, the spectrum of the radiation is obtained and the temperature of the radiation is read out from this spectrum. The temperature is proportional to the surface gravity of the apparent horizon as usual. Besides, in stationary cases we calculate the spectrum by using Parikh and Wilczek＇s null geodesic method and the result conforms to that obtained by using the Harnilton-Jacobi method. This is expected since the flamilton-Jacobi method applies to generic spacetimes, including stationary ones.
基金supported in part by NSFC under Grant No.12075231 and 12047502。
文摘Riemannian geometry, as a basis for general relativity, can be obtained from the more general Finsler geometry in terms of the Cartan connection and Chern connection, as discussed frequently in the literature. However, there are other gravity theories that can be made to be equivalent to general relativity but are based on non-Riemannian geometry. Famous examples are the Teleparallel and Symmetric Teleparallel gravity theories. In this paper, we show how to obtain the geometry for Teleparallel gravity from Finsler geometry in terms of a ‘Teleparallel type’ connection.
基金supported by the Fundamental Research Funds for the Central Universities(WK2030000036)the National Natural Science Foundation of China(12075233).
文摘The Wilson coefficients of the standard model effective field theory are subject to a series of positivity bounds.It has been shown that while the positivity part of the ultraviolet(UV)partial wave unitarity leads to the Wilson coefficients living in a convex cone,further including the nonpositivity part caps the cone from above.For Higgs scattering,a capped positivity cone was obtained using a simplified,linear unitarity condition without utilizing the full internal symmetries of Higgs scattering.Here,we further implement stronger nonlinear unitarity conditions from the UV,which generically gives rise to better bounds.We show that,for the Higgs case in particular,while the nonlinear unitarity conditions per se do not enhance the bounds,the fuller use of the internal symmetries do shrink the capped positivity cone significantly.
基金Supported in part by National Natural Science Foundation of China under Grant No.11235010
文摘We study the cosmology of a quintessence scalar held which is equivalent to a non-barotropic perfect fluid of constant pressure.The coincidence problem is alleviated by such a quintessence equation-of-state that interpolates between plateau of zero at large redshifts and plateau of minus one as the redshift approaches to zero.The quintessence Geld is neither a unified dark matter nor a mixture of cosmological constant and cold dark matter,relying on the facts that the quintessence density contrasts of sub-horizon modes would undergo a period of late-time dechne and the squared sound speeds of quintessence perturbations do not vanish.What a role does the quintessence play is dynamic dark energy,its clustering could remarkably reduce the growth rate of the density perturbations of non-relativistic matters.
基金Supported by the National Natural Science Foundation of China
文摘Ultracompact dark matter minihalos （UCMHs） would be formed during the early universe if there were large density perturbations. If dark matter can decay into particles described by the standard model, such as neutrinos, these objects would become potential astrophysical sources of emission which could be detected by in- struments such as IceCube. In this paper, we investigate neutrino signals from nearby UCMHs due to gravitino dark matter decay and compare these signals with the back- ground neutrino flux which is mainly from the atmosphere to obtain constraints on the abundance of UCMHs.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10588503, 10535060, and 10975128, the National Basic Research Program of China under Grant No 2007CB815401, and the Pujiang Talent Project of the Shanghai Science and Technology Committee under Grant No 06PJ14114.
文摘Noncommutative Chern-Simons （NCCS） theory is a workable description for the fractional quantum Hall fluid. We apply and generalize the NCCS theory to the physically important case with an edge. Prom relabeling symmetry of electrons and incompressibility of the fluid, we obtain a constraint and reduce the two-dimensional NCCS theory to a one-dimensional chiral Tomonaga-Luttinger liquid theory, which contains additional interaction terms. Further, we calculate one-loop corrections to the boson and electron propagators and obtain a new tunneling exponent, which agrees with experiments.
基金supported by the National Natural Science Foundation of China (Grant Nos.10535060/A050207,10975172 and 10821504)the National Basic Research Program of China (Grant No.2007CB815401)
文摘We propose a new holographic program of gravity in which we introduce a surface stress tensor.Our proposal differs from Verlinde's in several aspects.First,we use an open or a closed screen.Second,the temperature is not necessary,but a surface energy density and pressure are introduced.The surface stress tensor is proportional to the extrinsic curvature.Third,the energy we use is Brown-York energy and the equipartition theorem is violated by a non-vanishing surface pressure.We discuss holographic thermodynamics of a gas of weak gravity and find a chemical potential,and then show that Verlinde's program does not lead to reasonable thermodynamics.The holographic entropy is similar to the Bekenstein entropy bound.
基金Supported by NSF (10975128)973 Program of China (2007CB815401)
文摘I show the formulation of de Sitter Special Relativity （dS-SR） based on Dirac-Lu-Zou-Guo’s discussions. dS-SR quantum mechanics is formulated, and the dS-SR Dirac equation for hydrogen is suggested. The equation in the earth-QSO framework reference is solved by means of the adiabatic approach. It’s found that the fine-structure ＂constant＂ α in dS-SR varies with time. By means of the t-z relation of the ΛCDM model, α’s time-dependency becomes redshift z-dependent. The dS-SR’s predictions of △α/α agree with data of spectra of 143 quasar absorption systems, the dS-space-time symmetry is SO（3, 2） （i.e., anti-dS group） and the universal parameter R （de Sitter ratio） in dS-SR is estimated to be R ≈ 2.73×1012 ly. The effects of dS-SR become visible at the cosmic space-time scale （i.e., the distance 109 ly）. At that scale, dS-SR is more reliable than Einstein SR. The α-variation with time is evidence of SR with de Sitter symmetry.
基金National Natural Science Foundation of China(90403021)PhD Program Funds of the Education Ministry of China,Pujiang Talent Project of the Shanghai Science Technology Committee(06PJ14114)Hundred Talents Project of Shanghai Institute of Applied Physics
文摘In the strong uniform magnetic field, the noncommutative plane （NCP） caused by the lowest Landau level （LLL） effect, and QED with NCP （QED-NCP） are studied. Being similar to the condensed matter theory of quantum Hall effect, an effective filling factor f（B） is introduced to characterize the possibility that the electrons stay on the LLL. The analytic and numerical results of the differential cross section for the process of backward Compton scattering in accelerator with unpolarized or polarized initial photons are calculated. The existing data of BL38B2 in Spring-8 have been analyzed roughly and compared with the numerical predictions primitively. We propose a precise measurement of the differential cross sections of backward Compton scattering in a strong perpendicular magnetic field, which may reveal the effects of NCP.
