No abstract

Gravitational waves can probe general relativity in the extreme gravity regime. We study how the events detected so far by the LIGO-Virgo collaboration can probe higher-curvature corrections to general relativity, focusing on Einstein-dilaton-Gauss-Bonnet and dynamical Chern-Simons gravity. We find that the two events with a low-mass m ≈ 7M ⊙ BH (GW151226 and GW170608) place stringent constraints on Einstein-dilaton-Gauss-Bonnet gravity, α 1/2 EdGB 5.6 km, whereas dynamical Chern-Simons gravity remains unconstrained.

The transcription factors NF-B/Rel play a key role in regulating a diverse array of genes involved in cell growth, differentiation, and adaptive responses to environmental factors that are cell-and stimulus-specific (1). In the central nervous system, NF-B/Rel proteins are ubiquitously expressed in neurons and glia (2, 3) where, in addition to regulating physiological processes, they participate in pathological events associated with neurodegeneration (3, 4). Increased NF-B/Rel levels have been observed in the dying neurons of brains exposed to trauma and ischemia (5-8) as well as in brains of patients with Alzheimer's disease and Parkinson's disease (9 -11). Whether NF-B/Rel participates in a neurodegenerative program or otherwise in a neuroprotective process by increasing neuronal resistance to various noxae is still debated. Although many studies support the antiapoptotic effects of NF-B/Rel in cultured neurons (12-15), conflicting evidence has emerged from experimental models of pathological conditions affecting adult neurons. For example, some studies showed that NF-B/Rel mediates the neuroprotection elicited by the tumor necrosis factor in hippocampal cells (16,17) and promotes neuronal resistance to excitotoxicity (18) and ␤-amyloid-induced apoptosis (19). Other studies demonstrated that the activation of NF-B/Rel triggers neuronal degeneration after cerebral ischemia (6, 8) and mediates the glutamate-activated cell death program during excitotoxic insults to central neurons (4,20,21).NF-B/Rel proteins are a family of transcription factors composed of several members, including p50, p52, p65/RelA, RelB, and c-Rel, that form homo-and heterodimers capable of transmitting receptor signals to the nucleus (3,22). In resting cells, NF-B/Rel factors are retained in the cytoplasm by association with the inhibitory IB proteins. In stimulated cells, IB is phosphorylated and degradated, thus allowing the release and nuclear translocation of NF-B dimers. Recently, a more complex regulation of NF-B/Rel activation that involves modulatory phosphorylations has been emerging. The phosphorylation of NF-B/Rel components may operate to optimize their DNA binding and transcriptional activities, as well as functional interaction with coactivators (23). The diverse phenotypes of different NF-B/Rel knockout mice suggest that each NF-B/ Rel member serves unique physiological roles in vivo, presumably via the regulation of distinct sets of target genes. Thus, the opposite regulation of neuron survival by NF-B/Rel may very well depend on the activation of a distinct combination of subunits, resulting in the differential regulation of target genes and the induction of diverse genetic programs that dictate the cell fate (24 -26).In this study, we investigated the contribution of different NF-B/Rel proteins to the cell survival of brain neurons exposed to IL-1␤ 1 and glutamate, two common activators of NF-* This work was supported by grants from the Consiglio Nazionale delle Richerche (CNR 2000), the Italian Health Ministry, the Ital...

Gravitational wave observations of compact binaries allow us to test general relativity (and modifications thereof) in the strong and highly dynamical field regime of gravity. Here, we confront two extensions to general relativity, dynamical Chern-Simons, and Einstein-dilaton-Gauss-Bonnet theories, against the gravitational wave sources from the GWTC-1 and GWTC-2 catalogs by the LIGO-Virgo Collaboration. By stacking the posterior of individual events, we strengthen the constraint on the square root of the coupling parameter in Einstein-dilaton-Gauss-Bonnet gravity to ffiffiffiffiffiffiffiffiffiffiffi ffi α EdGB p < 1.7 km, but we are unable to place meaningful constraints on dynamical Chern-Simons gravity. Importantly, we also show that our bounds are robust to (i) the choice of general-relativity base waveform model, upon which we add modifications, (ii) unknown higher post-Newtonian order terms in the modifications to general relativity, (iii) the smallcoupling approximation, and (iv) uncertainties on the nature of the constituent compact objects.