Sourav Bhattacharya, Konstantinos F. Dialektopoulos, Theodore N. Tomaras
The maximum size of a bound cosmic structure is computed perturbatively as a function of its mass in the framework of the cubic galileon, proposed recently to model the dark energy of our Universe. Comparison of our results with observations constrains the matter-galileon coupling of the model to $0.033\lesssim α\lesssim 0.17$, thus improving previous bounds based solely on solar system physics.
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The cubic Galileon model containing the lowest non-trivial order action of the full Galileon action can produce the stable late-time cosmic acceleration. This model can have a significant role in the growth of structures. The signatures of the cubic Galileon model in the structure formation can be probed by the weak lensing statistics. Weak lensing convergence statistics is one of the strongest probes to the structure formation and hence it can probe the dark energy or modified theories of gravity models. In this work, we investigate the detectability of the cubic Galileon model from the $ Λ$C…
21 cm power spectrum in interacting cubic Galileon model
本研究探讨利用21 cm功率谱区分相互作用与非相互作用立方Galileon模型和ΛCDM模型的可行性，指出SKA1-mid这类干涉观测可依参数取值实现该探测。
Cubic Derivative Interactions and Asymptotic Dynamics of the Galileon Vacuum
本文应用动力系统理论的工具，揭示了具有立方导数相互作用项的伽利略模型真空相互作用的整体渐近结构。结果表明，与背景物质的存在下发生的情况相反，伽利略真空相互作用明显地改变了后期宇宙动力学。特别是，一个本地的晚时间吸引子表示幻影行为的出现，这是不可避免地与一个大的裂缝奇点。看来背景物质与伽利略的引力相互作用屏蔽了伽利略引力自相互作用的影响，从而消除了伽利略真空过程对晚期动力学的任何潜在修改。不像其他伽利略模型的灵感来自DGP的情况下，自加速的解决方案不会出现在这个模型。
Late-time acceleration in the coupled Cubic Galileon models
我们研究了包含线性势的线性和二次耦合立方Galileon模型。这些模型可以解释后期加速。在这些情况下，我们需要两个状态方程参数，即本征状态方程和有效状态方程，来检验宇宙是否在加速，因为冷暗物质和伽利略粒子之间存在耦合。事实证明，未来没有从加速阶段到幻影阶段的过渡。
We use N-body simulation to study the structure formation in the Cubic Galileon Gravity model where along with the usual kinetic and potential term we also have a higher derivative self-interaction term. We find that the large scale structure provides a unique constraining power for this model. The matter power spectrum, halo mass function, galaxy-galaxy weak lensing signal, marked density power spectrum as well as count in cell are measured. The simulations show that there are less massive halos in the Cubic Galileon Gravity model than corresponding $Λ$CDM model and the marked density power s…
In this paper, we study the effects of general relativistic corrections on the observed galaxy power spectrum in thawing class of cubic Galileon model with linear potential that preserves the shift symmetry. In this scenario, the observed galaxy power spectrum differs from the standard matter power spectrum mainly due to redshift space distortion (RSD) factor and relativistic effects. The RSD term enhances the matter power spectrum both at larger and smaller scales whereas the relativistic terms further enhance the matter power spectrum only at larger scales. In comparison with $Λ$CDM, the obs…
Matter bispectrum in cubic Galileon cosmologies
本文在协变立方Galileon理论的框架下得到了暗物质密度扰动的双谱。这个结果是通过一个半解析的方法在Galileon宇宙学的二阶微扰，假设高斯初始条件。特别是，我们表明，即使在存在大偏差的线性增长率w.r.t.在双谱水平上，这种偏差被减小到几个百分比。
We address the homogeneous in space and time (ST-homogeneous) Gödel-type metrics within the cubic galileon theory, a particular class of generalized galileon theories. We check the consistency of such spacetimes for a physically well-motivated matter content, namely, a perfect fluid and an electromagnetic field. In this scenario, we find that the admissible solutions impose constraints on the constant couplings ($c_{i}$'s) of the cubic galileon theory to ensure the consistency. Also, we show the existence of a vacuum completely causal solution.
We consider a disformal coupling between Standard Model matter and a cubic Galileon scalar sector, assumed to be a relict of some other physics that solves the cosmological constant problem rather than a solution in its own right. This allows the energy density carried by the Galileon scalar to be sufficiently small that it evades stringent constraints from the integrated Sachs-Wolfe effect, which otherwise rules out the cubic Galileon theory. Although the model with disformal coupling does not exhibit screening, we show there is a `screening-like' phenomenon in which the energy density carrie…
We investigate the generalized cubic covariant Galileon model, a kinetically driven dark energy model within the Horndeski class of theories. The model extends the cubic covariant Galileon by including power laws of the field derivatives in the K-essence and cubic terms which still allow for tracker solutions. We study the shape of the viable parameter space by enforcing stability conditions which include the absence of ghost, gradient and tachyon instabilities and the avoidance of strong coupling at early time. We study here the relevant effects of the modifications induced by the model on so…
We present for the first time an explicit exposition of quantum corrections within the cubic Galileon theory including the effect of quantum gravity, in a background- and gauge-invariant manner, employing the field-reparametrisation approach of the covariant effective action at 1-loop. We show that the consideration of gravitational effects in combination with the non-linear derivative structure of the theory reveals new interactions at the perturbative level, which manifest themselves as higher-operators in the associated effective action, which' relevance is controlled by appropriate ratios …
We revisit the cosmological dynamics of the cubic Galileon model in light of the recently proposed model-independent analyses of the Pantheon supernova data. At the background level, it is shown to be compatible with data and preferred over standard quintessence models. Furthermore, the model is shown to be consistent with the trans-Planckian censorship conjecture (as well as other Swampland conjectures). It is shown that for the given parametrization, the model fails to satisfy the bounds on the reconstructed growth index derived from the Pantheon data set at the level of linear~perturbations…
The Speed of Galileon Gravity
本文分析了耦合Galileon模型中引力波的传播速度，给出了状态方程$ω_ϕ=-1$和无鬼影的Minkowski极限。我们发现，引力波的传播速度远远超过光速，除非这些模型是立方伽利略子的小扰动和伽利略子的能量密度是次主导的一个占主导地位的宇宙学常数。在这种情况下，当与物质的耦合与Galileon拉格朗日量的立方项系数相联系时，双脉冲星的引力波传播速度的界可以满足，状态方程可以接近-1。这严重限制了伽利略模型所允许的宇宙学行为，我们不得不得出这样的结论：具有稳定闵可夫斯基极限的伽利略不能解释观测到的宇宙膨胀加速。此外，我们宇宙中任何次主导的伽利略分量都必须由立方项主导。对于这种引力子传播速度超过光速的模型，引力子可能变得不稳定，并可能衰变为光子对。它们也可以通过切伦科夫辐射发射光子。我们表明，这种快速的引力子到光子和切伦科夫辐射的衰减率实际上是可以忽略的。此外，引力信号和爆炸性天体物理事件发出的光之间的时间延迟可以证实引力的变化作用于宇宙的最大尺度。
Non-linear power spectrum and forecasts for Generalized Cubic Covariant Galileon
本研究针对下一代巡天对非线性尺度物质功率谱的建模需求，提出广义三次协变伽利略子模型的晕模型反应框架，修改ReACT软件验证精度后，分析模型修正的非线性效应并给出参数约束预测，证实非线性修正的关键作用。
We examine the stability of steady-state galileon accretion for the case of a Schwarzshild black hole. Considering the galileon action up to the cubic term in a static and spherically symmetric background we obtain the general solution for the equation of motion which is divided in two branches. By perturbing this solution we define an effective metric which determines the propagation of fluctuations. In this general picture we establish the position of the sonic horizon together with the matching condition of the two branches on it. Restricting to the case of a Schwarzschild background, we sh…
Numerical solutions for asymptotically flat rotating black holes in the cubic Galileon theory are presented. These black holes are endowed with a nontrivial scalar field and exhibit a non-Schwarzschild behaviour: faster than $1/r$ convergence to Minkowski spacetime at spatial infinity and hence vanishing of the Komar mass. The metrics are compared with the Kerr metric for various couplings and angular velocities. Their physical properties are extracted and show significant deviations from the Kerr case.
We study relativistic stars in Hordenski theories that evade the gravitational wave constraints and exhibit the Vainshtein mechanism, focusing on a model based on the cubic Galileon Lagrangian. We derive the scalar field profile for static spherically symmetric objects in asymptotically de Sitter space-time with a linear time dependence. The exterior solution matches to the black hole solution found in the literature. Due to the Vainshtein mechanism, the stellar structure is indistinguishable from that of General Relativity with the same central density as long as the radius of the star is sho…
Cubic Galileon massive gravity is a development of de Rham-Gabadadze-Tolly (dRGT) massive gravity theory is which the space of the Stueckelberg field is broken. We consider the cubic Galileon term as a scalar field coupled to the graviton filed. We present a detailed study of the cosmological aspects of this theory of gravity. We analyze self-accelerating solutions of the background equations of motion to explain the accelerated expansion of the Universe. Exploiting the latest Union2 Type Ia Supernovea (SNIa) dataset, which consists of 557 SNIa, we show that cubic Galileon massive gravity theo…
Null and timelike equatorial orbits are investigated in a family of hairy black holes in the cubic Galileon theory. These include rotating generalizations of static black hole metrics supporting a time-dependent scalar field. Depending on the coupling and rotation, the properties of the geodesics expectedly deviate from general relativity. In particular, it is found that stable circular geodesics only exist below a critical coupling, which is related to the existence of an outermost stable circular orbit. Focusing on the strong-field region, images of an accretion disk are also produced to hig…
Recently a cubic Galileon cosmological model was derived by the assumption that the field equations are invariant under the action of point transformations. The cubic Galileon model admits a second conservation law which means that the field equations form an integrable system. The analysis of the critical points for this integrable model is the main subject of this work. To perform the analysis, we work on dimensionless variables different from that of the Hubble normalization. New critical points are derived while the gravitational effects which follow from the cubic term are studied.
In this paper we generalize the dynamical systems analysis of the cubic galileon model previously investigated in \cite{rtgui} by including self-interaction potentials beyond the exponential one. It will be shown that, consistently with the results of \cite{rtgui}, the cubic self-interaction of the galileon vacuum appreciably modifies the late-time cosmic dynamics by the existence of a phantom-like attractor (among other super-accelerated solutions that are not of interest in the present investigation). In contrast, in the presence of background matter the late-time cosmic dynamics remains pra…
We present a perturbative treatment of nonlinear galaxy clustering in the context of the cubic Galileon modified gravity model, in terms of 2nd order Lagrangian Perturbation theory and an extension of ellipsoidal collapse that includes Vainshtein screening. We numerically implement such prescriptions in the approximate PINOCCHIO code, and use it to generate realisations of the matter density field and halo catalogues with different prescriptions for ellipsoidal collapse. We investigate the impact of three different approximations in the computation of collapse times on the halo mass function, …
Cubic Galileon Gravity in the CMB
本文提出含立方伽利略算子的早期暗能量模型 $\mathcal{G}$EDE，利用 Planck PR4 CMB 和 Pantheon+ 超新星数据检验，发现其比标准 EDE 拟合更好且 $H_0$ 更高，并扩展 EFTCAMB 以支持 Horndeski 类修正引力研究。
We consider a scalar field which is generallly non-minimally coupled to gravity and has a characteristic cubic Galilean-like term in the kinetic part of the action, in presence of a generic self-interaction as a candidate Dark Energy model. The system is dynamically analyzed and novel fixed points with perturbative stability are demonstrated. Evolution of the system is numerically studied near a novel fixed point which owes its existance to the Galileon character of the model. It turns out that demanding the stability of this novel fixed points puts strong restriction on the allowed non-minima…
Fully consistent rotating black holes in the cubic Galileon theory
本文利用谱方法在 3+1 形式表述下首次实现了立方 Galileon 理论中旋转黑洞的完全一致计算，发现其质量消失且不遵循黑洞热力学第零定律。
We find and study the properties of black hole solutions for a subclass of Horndeski theory including the cubic Galileon term. The theory under study has shift symmetry but not reflection symmetry for the scalar field. The Galileon is assumed to have linear time dependence characterized by a velocity parameter. We give analytic 3-dimensional solutions that are akin to the BTZ solutions but with a non-trivial scalar field that modifies the effective cosmological constant. We then study the 4-dimensional asymptotically flat and de Sitter solutions. The latter present three different branches acc…
In this paper we perform a thorough dynamical systems analysis of the cubic galileon model non-minimally coupled to the dark matter. Three well-known classes of interacting models are considered where the energy exchange between the dark components is a function of the dark matter density and of the dark energy density: $Q_1=3αHρ_m$, $Q_2=3βρ_m\dotϕ$ and $Q_3=3 εH ρ_ϕ$, respectively. We are able to show the global asymptotic dynamics of the model for the exponential potential in a homogeneous and isotropic background. The cosmological implications of the proposed scenarios are explored and it …
We consider the cosmological dynamics of the cubic Galileon field model interacting with dark matter, where the interaction between the cosmic dark sectors is proportional to Hubble parameter and dark energy density. The background field equations are converted into an autonomous dynamical system of first order equations using suitable dimensionless variables. The fixed points are determined and their stability analyzed by means of the eigenvalue method. The analysis of the stability of the fixed points along that of the avoidance of ghosts and Laplacian instabilities implies negative coupling…
Cosmological Constraints on Minimal Cubic Galileon Models in Teleparallel Gravity
在遥平行引力框架下，利用超新星、宇宙计时器、SH0ES和重子声学振荡数据约束三次伽利略宇宙学模型，发现二次势固定b1模型拟合最优，但BIC仍偏好ΛCDM。
Galileon Radiation from Binary Systems
我们计算的功率发射的标量模式的二元系统，包括二元pixars，与最一般的Galileon有效场论的共形耦合，考虑周围的扰动静态，球形背景。虽然这种方法是有效的计算功率在立方Galileon的情况下，在这里，我们发现，如果四次或五次Galileon占主导地位，对于现实的脉冲星系统的经典微扰展开球对称背景打破（虽然量子有效理论是定义良好的）。基本原因是，涨落的运动方程实际上是一维的。这导致许多多极子以相等的强度辐射，而不是正常的闵可夫斯基时空和立方伽利略的情况下，增加多极子被抑制的轨道速度的增加功率。我们考虑两种情况，微扰理论给出了值得信赖的结果：（1）当两个轨道物体的质量之间有一个大的层次，（2）当我们选择的尺度，使得四次Galileon只开始主导的距离小于脉冲星频率的倒数。未来的计算与充分Galileon帐户的Vainshtein机制的影响被认为是。
Spherical Collapse in covariant Galileon theory
在本文中，我们研究的背景下，最近推出的伽利略场论的球形物质过密度的演变。我们的分析认为，在四维完全协变拉格朗日。这个理论由一个势项和一个标准动力学项、一个立方动力学项和两个附加项组成，其中包括伽利略子和度规之间的耦合，以保持伽利略子在弯曲时空中的原始性质。在这里，我们扩展了以前的研究，认为这两个精髓和立方条款，通过集中在最后两个条款的作用。我们考虑的背景演变是由跟踪器解决方案驱动的。研究标量扰动的非线性政权，我们发现的参数模型的约束。我们将展示新的条款如何有助于崩溃阶段，以及它们如何修改物理参数，如线性化密度对比度和维里过密度。结果表明，伽利略基本上修改了坍缩的动力学，从而使之有可能在观测上约束这个理论的参数。
Alleviating the $H_0$ and $σ_8$ tensions in the interacting cubic covariant Galileon model
本文研究暗物质与暗能量相互作用的三次Galileon模型，通过构建自治动力系统并分析精确ICG与近似TICG解，发现TICG模型能同时缓解$H_0$和$S_8$张力，而ICG模型仅缓解$H_0$张力。
Scrutinizing black hole stability in cubic vector Galileon theories
研究三次矢量Galileon理论中毛黑洞的线性稳定性，发现其在角向存在拉普拉斯不稳定性及径向传播速度病态，但引入矢量场质量后，无毛Schwarzschild黑洞解满足所有线性稳定性条件。
Hamiltonian of galileon field theory
本文详细计算了单伽利略场论的哈密顿量，并跟踪了所有的表面项。本文计算了三阶单伽利略场与点源耦合的静态球对称位形的能量，结果表明，解的2个分支具有大小相等、符号相反的能量，其符号由动力学项$α_2$的系数决定.此外，能量在短距离（紫外线）制度的主导立方项，即使源是发散的起源。我们认为，负性的起源是由于在相应的分支中的点源的存在下的幽灵般的模式。这似乎是鬼不稳定性的非线性表现。
Galileon versus Quintessence: A comparative phase space analysis and late-time cosmic relevance
本文比较了轻质量伽利略模型与标准Quintessence在晚期宇宙加速中的相空间特性，发现伽利略模型无稳定加速吸引子，而Quintessence在双曲余弦势下可提供稳定德西特吸引子。
In Einstein's general relativity, gravity is mediated by a massless metric field. The extension of general relativity to consistently include a mass for the graviton has profound implications for gravitation and cosmology. Salient features of various massive gravity theories can be captured by Galileon models, the simplest of which is the cubic Galileon. The presence of the Galileon field leads to additional gravitational radiation in binary pulsars where the Vainshtein mechanism is less suppressed than its fifth-force counterpart, which deserves a detailed confrontation with observations. We …
Spontaneous "Scalar-Vector Galileons" from "Weyl bi-Connection" model
Weyl双连接模型体现了自动产生Galileon结构的自然框架。结果表明，该框架可以解释标量Galileon，矢量Galileon以及它们之间的相互作用，通过推广外尔非度规。所以它可以被解释为伽利略的几何实现。非度量部分具有$U(1)$规范不变性。有趣的是，这个结果并不平凡，因为伽利略结构是自发出现的，而不是要求没有奥斯特罗格拉茨基幽灵。这一事实表明，外尔双连接模型和奥斯特罗格拉茨基幽灵的缺席之间可能存在更深层次的概念关系。
EFT-Ramses: a code to simulate the effective field theory of dark energy
为应对宇宙常数理论挑战，探索动态暗能量和修正引力模型，介绍EFT-RAMSES代码，它将暗能量有效场论框架嵌入数值管道，整合多种理论到单一方程，通过N体模拟验证，为暗能量和修正引力精确宇宙学测试提供强大通用计算工具。
Nonlinear Dynamics of 3D Massive Gravity
本文研究了Bergshoeff、Hohm和Townsend提出的三维“新质量引力”理论的非线性经典动力学。我们发现，该理论通过显着高度非平凡的一致性检查在非线性水平。特别是，我们表明：（1）在理论的解耦极限，螺旋度-0模式的相互作用是由一个单一的立方项-所谓的立方伽利略-以前发现的背景下的DGP模型和某些四维大质量引力。(2)度规的共形模式与退耦极限下的螺旋度-0模式一致。远离这个限制，前者的非线性动力学是由伽利略相互作用的某种概括来描述的，就像伽利略本身有一个适定的柯西问题。(3)我们给出了一个非微扰参数的基础上存在的额外的对称性，完整的理论不会导致任何额外的自由度，这表明一个3D模拟的4D Boulware-Deser鬼是不存在于这个理论。最后，我们推广了“新质量引力”，构造了一类具有上述性质的三维三阶质量模型。
We derive the profile of a vector field coupled to matter on a static and spherically symmetric background in the context of generalized Proca theories. The cubic Galileon self-interaction leads to the suppression of a longitudinal vector component due to the operation of the Vainshtein mechanism. For quartic and sixth-order derivative interactions, the solutions consistent with those in the continuous limit of small derivative couplings correspond to the branch with the vanishing longitudinal mode. We compute the corrections to gravitational potentials outside a compact body induced by the ve…
We investigate the renormalization structure of scalar Galileons in flat spacetime. We explicitly calculate the ultraviolet divergent one-loop contributions to the 2-point, 3-point, 4-point, and 5-point functions. We discuss the structure of the counterterms and their hierarchy within an effective field theory expansion. We comment on different resummation schemes, including a geometric resummation for which our results could be generalized to arbitrary n-point functions.
The renormalization of fluctuating branes, the Galileon and asymptotic safety
我们考虑嵌入在平坦（d+1）维空间中的d维超曲面（膜）的重整化。我们参数化的截断有效行动的几何不变量建立从外在和内在的曲率。我们研究了耦合的重整化群运行，并探索了不动点结构。我们发现了一个紫外线不动点的证据类似的一个潜在的渐近安全的情况下的重力。我们还研究了伽利略理论的结构，它可以在非相对论的限制，是保存在量子水平。
Matter perturbations in Galileon cosmology
我们研究了伽利略宇宙学中物质密度扰动的演化，其中晚期宇宙加速可以通过场动能实现。在平坦时空中，当存在五个满足伽利略对称性的协变拉格朗日量${cal L}_i$（$i=1,...,5$）时，我们得到了线性阶的完全微扰方程.在亚视界尺度准静态近似下导出了物质扰动方程和有效引力势方程。这种近似可以再现与大尺度结构相关的波长的高精度的完整的数值解。在宇宙背景膨胀历史约束的模型参数下，物质扰动的增长率大于LCDM模型，增长指数$gamma$今天通常小于0.4。我们还发现，即使在宇宙微波背景（CMB）温度各向异性的积分萨克斯-沃尔夫（ISW）效应的大尺度下，有效引力势在从物质时代到宇宙加速时代的过渡过程中也表现出时间上的增长.这些性质有助于在未来的高精度观测中区分Galileon模型和LCDM模型。
Positivity bounds - constraints on any low-energy effective field theory imposed by the fundamental axioms of unitarity, causality and locality in the UV - have recently been used to constrain various effective field theories relevant for cosmology. However, to date most of these bounds have assumed that there is a single Lorentz-invariant vacuum in which all fields have zero expectation value and in many cosmologically relevant models this is not the case. We explore ways to overcome this limitation by investigating a simple example model, the covariant Galileon, which possesses a one-paramet…
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