%0 Generic %1 romano2023answers %A Romano, Joseph D. %A Allen, Bruce %D 2023 %K tifr %T Answers to frequently asked questions about the pulsar timing array Hellings and Downs correlation curve %U http://arxiv.org/abs/2308.05847 %X We answer frequently asked questions (FAQs) about the Hellings and Downs correlation curve -- the "smoking-gun" signature that pulsar timing arrays (PTAs) have detected gravitational waves (GWs). Many of these questions arise because of intuition based on how ground-based interferometers like LIGO respond to GWs. These have arms that are short (km scale) compared to the wavelengths of the GWs that they detect (hundreds to thousands of km). In contrast, PTAs respond to GWs whose wavelengths (tens of light-years) are much shorter than their arms (a typical PTA pulsar is thousands of light-years from Earth). To elucidate this, we calculate the exact response of a öne-arm, one-way" detector to a passing GW, and compare it in the "short-arm" (LIGO-like) and "long-arm" (PTA) limits. This provides qualitative and quantitative answers to many questions about the Hellings and Downs correlation. The resulting "FAQ sheet" should help in understanding the "evidence for GWs" recently announced by several PTA collaborations.

@misc{romano2023answers, abstract = {We answer frequently asked questions (FAQs) about the Hellings and Downs correlation curve -- the "smoking-gun" signature that pulsar timing arrays (PTAs) have detected gravitational waves (GWs). Many of these questions arise because of intuition based on how ground-based interferometers like LIGO respond to GWs. These have arms that are short (km scale) compared to the wavelengths of the GWs that they detect (hundreds to thousands of km). In contrast, PTAs respond to GWs whose wavelengths (tens of light-years) are much shorter than their arms (a typical PTA pulsar is thousands of light-years from Earth). To elucidate this, we calculate the exact response of a "one-arm, one-way" detector to a passing GW, and compare it in the "short-arm" (LIGO-like) and "long-arm" (PTA) limits. This provides qualitative and quantitative answers to many questions about the Hellings and Downs correlation. The resulting "FAQ sheet" should help in understanding the "evidence for GWs" recently announced by several PTA collaborations.}, added-at = {2023-08-14T07:12:21.000+0200}, author = {Romano, Joseph D. and Allen, Bruce}, biburl = {https://www.bibsonomy.org/bibtex/25f6d1f554a6d3fd762dc1198ab32e059/citekhatri}, description = {Answers to frequently asked questions about the pulsar timing array Hellings and Downs correlation curve}, interhash = {b1c07fbfe12aadafa86be3396d860944}, intrahash = {5f6d1f554a6d3fd762dc1198ab32e059}, keywords = {tifr}, note = {cite arxiv:2308.05847Comment: 16 pages, 11 figures}, timestamp = {2023-08-14T07:12:21.000+0200}, title = {Answers to frequently asked questions about the pulsar timing array Hellings and Downs correlation curve}, url = {http://arxiv.org/abs/2308.05847}, year = 2023 }