Signature of supersymmetry from the early universe
Physical review. D. Particles, fields, gravitation, and cosmology/Physical review. D, Particles, fields, gravitation, and cosmology,
05/2012
Journal Article
A
bstract
Scattering amplitudes at weak coupling are highly constrained by Lorentz invariance, locality and unitarity, and depend on model details only through coupling constants and the particle ...content of the theory. For example, four-particle amplitudes are analytic for contact interactions and have simple poles with appropriately positive residues for tree-level exchange. In this paper, we develop an understanding of inflationary correlators which parallels that of flat-space scattering amplitudes. Specifically, we study slow-roll inflation with weak couplings to extra massive particles, for which all correlation functions are controlled by an approximate conformal symmetry on the boundary of the spacetime. After systematically classifying all possible contact terms in de Sitter space, we derive an analytic expression for the four-point function of conformally coupled scalars mediated by the tree-level exchange of massive scalars. Conformal symmetry implies that the correlator satisfies a pair of differential equations with respect to spatial momenta, encoding bulk time evolution in purely boundary terms. The absence of unphysical singularities (and the correct normalization of physical ones) completely fixes this correlator. Moreover, a “spin-raising” operator relates it to the correlators associated with the exchange of particles with spin, while “weight-shifting” operators map it to the four-point function of massless scalars. We explain how these de Sitter four-point functions can be perturbed to obtain inflationary three-point functions. Using our formalism, we reproduce many classic results in the literature, such as the three-point function of slow-roll inflation, and provide a complete classification of all inflationary three- and four-point functions arising from weakly broken conformal symmetry. Remarkably, the inflationary bispectrum associated with the exchange of particles with arbitrary spin is completely characterized by the soft limit of the simplest scalar-exchange four-point function of conformally coupled scalars and a series of contact terms. Finally, we demonstrate that the inflationary correlators contain flat-space scattering amplitudes via a suitable analytic continuation of the external momenta, which can also be directly connected with the signals for particle production seen in the squeezed limit.
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bstract
Sum rules connecting low-energy observables to high-energy physics are an interesting way to probe the mechanism of inflation and its ultraviolet origin. Unfortunately, such sum rules have ...proven difficult to study in a cosmological setting. Motivated by this problem, we investigate a precise analogue of inflation in anti-de Sitter spacetime, where it becomes dual to a slow renormalization group flow in the boundary quantum field theory. This dual description provides a firm footing for exploring the constraints of unitarity, analyticity, and causality on the bulk effective field theory. We derive a sum rule that constrains the bulk coupling constants in this theory. In the bulk, the sum rule is related to the speed of radial propagation, while on the boundary, it governs the spreading of nonlocal operators. When the spreading speed approaches the speed of light, the sum rule is saturated, suggesting that the theory becomes free in this limit. We also discuss whether similar results apply to inflation, where an analogous sum rule exists for the propagation speed of inflationary fluctuations.
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bstract
A key insight of the bootstrap approach to cosmological correlations is the fact that all correlators of slow-roll inflation can be reduced to a unique building block — the four-point ...function of conformally coupled scalars, arising from the exchange of a massive scalar. Correlators corresponding to the exchange of particles with spin are then obtained by applying a spin-raising operator to the scalar-exchange solution. Similarly, the correlators of massless external fields can be derived by acting with a suitable weight-raising operator. In this paper, we present a systematic and highly streamlined derivation of these operators (and their generalizations) using tools of conformal field theory. Our results greatly simplify the theoretical foundations of the cosmological bootstrap program.
Partially massless fields during inflation Baumann, Daniel; Goon, Garrett; Lee, Hayden ...
The journal of high energy physics,
04/2018, Volume:
2018, Issue:
4
Journal Article
Peer reviewed
Open access
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bstract
The representation theory of de Sitter space allows for a category of partially massless particles which have no flat space analog, but could have existed during inflation. We study the ...couplings of these exotic particles to inflationary perturbations and determine the resulting signatures in cosmological correlators. When inflationary perturbations interact through the exchange of these fields, their correlation functions inherit scalings that cannot be mimicked by extra massive fields. We discuss in detail the squeezed limit of the tensor-scalar-scalar bispectrum, and show that certain partially massless fields can violate the tensor consistency relation of single-field inflation. We also consider the collapsed limit of the scalar trispectrum, and find that the exchange of partially massless fields enhances its magnitude, while giving no contribution to the scalar bispectrum. These characteristic signatures provide clean detection channels for partially massless fields during inflation.
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bstract
Much of the structure of cosmological correlators is controlled by their singularities, which in turn are fixed in terms of flat-space scattering amplitudes. An important challenge is to ...interpolate between the singular limits to determine the full correlators at arbitrary kinematics. This is particularly relevant because the singularities of correlators are not directly observable, but can only be accessed by analytic continuation. In this paper, we study rational correlators — including those of gauge fields, gravitons, and the inflaton — whose only singularities at tree level are poles and whose behavior away from these poles is strongly constrained by unitarity and locality. We describe how unitarity translates into a set of cutting rules that consistent correlators must satisfy, and explain how this can be used to bootstrap correlators given information about their singularities. We also derive recursion relations that allow the iterative construction of more complicated correlators from simpler building blocks. In flat space, all energy singularities are simple poles, so that the combination of unitarity constraints and recursion relations provides an efficient way to bootstrap the full correlators. In many cases, these flat-space correlators can then be transformed into their more complex de Sitter counterparts. As an example of this procedure, we derive the correlator associated to graviton Compton scattering in de Sitter space, though the methods are much more widely applicable.
Positivity from Cosmological Correlators Green, Daniel; Huang, Yiwen; Shen, Chia-Hsien ...
The journal of high energy physics,
04/2024, Volume:
2024, Issue:
4
Journal Article
Peer reviewed
Open access
A
bstract
Effective field theories in flat space and in anti-de Sitter space are constrained by causality and unitarity, often in the form of positivity bounds. Similar bounds have been harder to ...demonstrate in cosmological backgrounds, where the roles of unitarity and causality are more obscure. Fortunately, the expansion of the universe ensures that late-time cosmological correlators are effectively classical and the role of unitarity is played by classical statistical inequalities. For multi-field inflation, the resulting positivity constraints have long been known in terms of the Suyama-Yamaguchi inequality. In this paper, we demonstrate that similar statistical bounds imply nontrivial constraints for massive fields in the early universe. We show that any real anomalous dimensions for principal series fields in de Sitter space must be positive. We also derive a limit on the amplitude of particular oscillatory signals from inflation, including those arising in cosmological collider physics. Finally, we demonstrate that these constraints manifest themselves directly in the two-point statistics of matter and galaxies that will be measured in upcoming surveys.
Catheter based renal denervation (RDN) has emerged as a novel treatment for hypertension in patients. However, the mechanisms by which RDN lowers arterial pressure are unclear. We hypothesize that an ...interaction between afferent and efferent renal nerves and renal inflammation contributes to hypertension. Specifically, we hypothesized an interaction between afferent renal nerves and the inflammatory cytokine IL‐1β contributes to the pathogenesis of hypertension in the DOCA‐salt mouse. To test this hypothesis, we compared the effect of total RDN (TRDN), afferent RDN (ARDN) on pathogenesis DOCA‐salt hypertension to that observed in IL‐1R knockout mice. We also measured the effect of administration of the IL‐1R antagonist anakinra on arterial pressure in DOCA‐salt mice.
10‐week‐old male C57BL6/J mice were implanted with radio‐telemetry probes in the carotid artery for measurement of arterial pressure. DOCA was administered via subcutaneous implantation of a silicon pellet containing 50 mg of DOCA. Sham mice received a drug free silicon pellet. Uni‐nephrectomy, pellet insertion, salt treatment, TRDN or ARDN were all performed on the same day. TRDN was performed through surgical ablation and peri‐axonal application of 10% phenol. ARDN was performed through peri‐axonal application of capsaicin. IL‐1R knockout mice and the IL‐1R antagonist anakinra were used in two separate groups to suppress activation of IL‐1R. Anakinra (75mg/kg) was delivered via intraperitoneal injection daily 10 days post induction of hypertension. Baseline arterial pressure was measured beginning 3 days prior to induction of DOCA‐salt hypertension by radiotelemetry. Separate cohorts of mice were generated for protein quantification and histology, with urine and kidneys harvested 21 days post induction of DOCA‐salt hypertension. Cytokine protein quantification was obtained through Multiplex ELISA. All values reported are mean + SEM.
The mean arterial pressure (MAP) elevation in the sham treated DOCA‐salt mice (+43 ± 1 mmHg increase from baseline during the 3rd week of the study) was attenuated by ~40% by TRDN (+25.9 ± 4 mmHg) and by ~44% in ARDN DOCA‐salt mice (+24.1 ± 3 mmHg). Renal cytokines and chemokines were increased in DOCA‐salt compared to sham treated mice. IL‐1α and IL‐1β were both increased in DOCA‐salt kidneys (112.4 ± 19.2 pg/mg and 2.1 ± 0.4 pg/mg respectively) compared to sham kidneys (31.98 ± 4.4 pg/mg and 0.36 ± 0.06 pg/mg respectively). The DOCA‐salt induced increase in MAP in IL‐1R Knockout mice was similar to sham DOCA‐salt mice (+39.1 ± 1 mmHg). In contrast, Anakinra treatment attenuated the increase in MAP similar to TRDN and ARDN mice (+22.4 ± 4 mmHg). The difference in outcome between the knockout and antagonist group suggests compensation by other inflammatory factors. The comparable attenuation in the MAP response to DOCA‐salt ARDN and Anakinra treated groups is consistent with a common mechanism of action. We hypothesize that intrarenal IL‐1b activates sympathoexcitatory renal afferent nerves to increase MAP in DOCA‐salt mice. Future studies are needed to directly test this hypothesis.
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