@inproceedings{15296, abstract = {In this paper we build a constructive algorithm that returns a rectifiable curve that connects two points in a weakly convex set in a Hilbert space. We have proven that this algorithm converges and obtained an estimate on the curve’s length and compare the length of the curve obtained to known results.}, author = {Lopushanski, Mariana and Ivanov, Grigory}, booktitle = {AIP Conference Proceedings}, issn = {1551-7616}, location = {Virtual}, number = {1}, publisher = {AIP Publishing}, title = {{A constructive algorithm for building rectifiable curves in weakly convex sets}}, doi = {10.1063/5.0195908}, volume = {3030}, year = {2024}, } @inproceedings{17651, abstract = {A decade after their first discovery, the origin of giant supermassive black holes (SMBHs), with masses in excess of 109 Msolar, at redshifts as early as z > 6, remains a puzzle. One possibility is that stellar-mass ``seed'' BHs, left behind by the first stars, accrete gas at close to the Eddington limit during a large fraction (>~ 50%) of the time. While maintaining such a high accretion rate may itself be difficult, here we focus on another, less commonly discussed problem in this scenario: unless BH seed formation and growth are preferentially suppressed in less massive protogalaxies, the mass density in M~106Msolar SMBHs at z ~ 6 already exceeds the locally observed SMBH mass density by several orders of magnitude. We show that the X-rays from the earliest accreting BHs themselves can cause a self-regulation, by partially ionizing and heating the intergalactic medium (IGM). This ``global warming'' suppresses the formation and growth of subsequent generations of BHs in low-mass halos, and can produce excellent agreement with recent estimates of the z = 6 SMBH mass function, without impeding the growth of the largest (M>~109Msolar) holes, which reside in the most massive galaxies that formed first. The proposed gravitational-wave observatory eLISA could detect several tens of major mergers between SMBHs at z > 6.}, author = {Haiman, Zoltán and Tanaka, Takamitsu and Perna, Rosalba}, booktitle = {AIP Conference Proceedings}, issn = {0094-243X}, location = {Kyoto, Japan}, pages = {303--308}, publisher = {American Institute of Physics}, title = {{Self-regulating the early growth of black holes through global warming}}, doi = {10.1063/1.4754372}, volume = {1480}, year = {2012}, } @inproceedings{17664, abstract = {Supermassive black holes (SMBHs) are common in local galactic nuclei, and SMBHs as massive as several billion solar masses already exist at redshift z=6. These earliest SMBHs may arise by the combination of Eddington-limited growth and mergers of stellar-mass seed BHs left behind by the first generation of metal-free stars, or by the rapid direct collapse of gas in rare special environments where the gas can avoid fragmenting into stars. In this contribution, I review these two competing scenarios. I also briefly mention some more exotic ideas and how the different models may be distinguished in the future by LISA and other instruments.}, author = {Haiman, Zoltán and Whalen, Daniel J. and Bromm, Volker and Yoshida, Naoki}, booktitle = {AIP Conference Proceedings}, issn = {0094-243X}, location = {Austin, TX, United States}, number = {1}, pages = {215--224}, publisher = {American Institute of Physics}, title = {{The origin and detection of high-redshift supermassive black holes}}, doi = {10.1063/1.3518857}, volume = {1294}, year = {2010}, } @inproceedings{17751, abstract = {With the help of numerical simulations, we examine two aspects of feedback from the first generation of stars on later star formation. First, we investigate the impact of relic HII regions on forming halos. We find that the positive and negative effects of such feedback nearly cancel because the increase in entropy due to heating is balanced by the increase in the H 2 fraction due to the free electrons. However, these halos can be delayed more easily by a background Lyman-Werner flux. Second, we show that HD cooling is important in halos which have been ionized and allowed to recombine. Gas is allowed to cool to the CMB temperature at densities around n∼10 4cm-3, reducing the accreted mass by a factor of a few. However, as the collapse proceeds, the central gas density exceeds the critical density of HD and heats until HD cooling is no longer important. Therefore the behaviour of the (smaller mass) core is relatively unaffected by HD cooling.}, author = {Bryan, Greg L. and McGreer, Ian D. and Mesinger, Andrei and Haiman, Zoltán}, booktitle = {AIP Conference Proceedings}, issn = {0094-243X}, location = {Santa Fe, NM, United States}, publisher = {American Institute of Physics}, title = {{Feedback effects on population III star formation}}, doi = {10.1063/1.2905582}, year = {2008}, } @inproceedings{18736, abstract = {Empirical studies of the first generation of stars and quasars will likely become feasible within the next decade in several different wavelength bands. Microwave anisotropy experiments, such as MAP or Planck, will set constraints on the ionization history of the intergalactic medium due to these sources. In the infrared, the Next Generation Space Telescope (NGST) will be able to directly detect sub-galactic objects at redshifts z>10. In the optical, data from the Hubble Deep Field already places a constraint on the abundance of high-redshift quasars. However, the epoch of the first quasars might be first probed in X-ray bands, by instruments such as the Chandra X-ray Observatory (CXO) and the X-ray Multi-mirror Mission (XMM). In a 500 Ksec integration, CXO reaches a sensitivity of 2x10-16 erg/s cm^2. Based on simple hierarchical CDM models, we find that at this flux threshold approx. 100 quasars might be detectable from redshifts z>5, and approx. 1 quasar at z=10, in each 17x17 arcmin field. Measurement of the power spectrum of the unresolved soft X-ray background will further constrain models of faint, high-redshift quasars.}, author = {Haiman, Zoltán}, booktitle = {AIP Conference Proceedings}, issn = {0094-243X}, location = {Bologna, Italy}, number = {1}, pages = {140--149}, publisher = {AIP Publishing}, title = {{Probing the cosmic dark age in X-rays}}, doi = {10.1063/1.1434627}, volume = {599}, year = {2001}, } @article{18743, abstract = {Over the coming decade, the observational samples available for studies of cluster abundance evolution will increase from tens to hundreds, or possibly to thousands, of clusters. Here we assess the power of future surveys to determine cosmological parameters. We quantify the statistical differences among cosmologies, including the effects of the cosmic equation of state parameter w, in mock cluster catalogs simulating a 12 deg^2 Sunyaev-Zel’dovich Effect (SZE) survey and a deep 10^4 deg^2 X-ray survey. The constraints from clusters are complementary to those from studies of high-redshift Supernovae (SNe), CMB anisotropies, or counts of high-redshift galaxies. Our results indicate that a statistical uncertainty of a few percent on both Ωm and w can be reached when cluster surveys are used in combination with any of these other datasets.}, author = {Haiman, Zoltán}, issn = {0094-243X}, journal = {AIP Conference Proceedings}, location = {Austin, TX, United States}, number = {1}, pages = {303--309}, publisher = {AIP}, title = {{Clusters in the precision cosmology era}}, doi = {10.1063/1.1419569}, volume = {586}, year = {2001}, } @article{18747, abstract = {Warm Dark Matter (WDM) models have recently been resurrected to resolve apparent conflicts of Cold Dark Matter (DM) models with observations. Endowing the DM particles with non-negligible velocities causes free-streaming, which suppresses the primordial power spectrum on small scales. The choice of a root-mean-square velocity dispersion v(rms) = 0.05 km/s at redshift z=0 (corresponding to a particle mass of 1 keV if the WDM particles are fermions decoupling while relativistic) helps alleviate most, but probably not all, of the small-scale problems faced by CDM. An important side-effect of the particle velocities is the severe decrease in the number of collapsed halos at high redshift. This is caused both by the loss of small-scale power, and by the delay in the collapse of the smallest individual halos (with masses near the effective Jeans mass of the DM). The presence of early halos is required in order (1) to host either early quasars or galaxies that can reionize the universe by redshift z=5.8, and (2) to allow the growth of the supermassive black hole believed to power the recently discovered quasar SDSS 1044-1215 at this redshift. We quantify these constraints using a modified Press-Schechter formalism, and find v(rms) < 0.04 km/s (or m_X > 1 keV). If future observations uncover massive black holes at z > 10, or reveal that reionization occurred at z > 10, this could conclusively rule out WDM models as the solution to the small-scale crisis of the CDM paradigm.}, author = {Haiman, Zoltán and Barkana, Rennan and Ostriker, Jeremiah P.}, issn = {0094-243X}, journal = {AIP Conference Proceedings}, number = {1}, pages = {136--142}, publisher = {AIP Publishing}, title = {{Warm Dark Matter, small scale crisis, and the high redshift universe}}, doi = {10.1063/1.1419543}, volume = {586}, year = {2001}, }