It has recently been pointed out that shortly after the electroweak phase transition (t≃10−11 sec... more It has recently been pointed out that shortly after the electroweak phase transition (t≃10−11 sec , T≃100–200 GeV ) there was a period of very effective baryon (and lepton) number violation driven by non-perturbative effects arising from the electroweak anomaly. Here we argue that as a result of these electroweak interactions the total asymmetry in leptons must be equal and opposite to the baryon asymmetry: L≡∑iLi=Le+Lμ+Lr=−B. Since the individual lepton numbers can be positive or negative, this does not preclude any large individual contribution, i.e., |Li|>B. This fact has important consequences for primordial nucleosynthesis if |Li|≳1.
We search for nearby, isolated, accreting, "stellar-mass" (3 to 100M) black holes. Models suggest... more We search for nearby, isolated, accreting, "stellar-mass" (3 to 100M) black holes. Models suggest a synchrotron spectrum in visible wavelengths and some emission in X-ray wavelengths. Of 3.7 million objects in the Sloan Digital Sky Survey Early Data Release, about 150,000 objects have colors and properties consistent with such a spectrum, and 87 of these objects are X-ray sources from the ROSAT All Sky Survey. Thirty-two of these have been confirmed not to be black-holes using optical spectra. We give the positions and colors of these 55 black-hole candidates, and quantitatively rank them on their likelihood to be black holes. We discuss uncertainties the expected number of sources, and the contribution of black holes to local dark matter.
Cosmic microwave background (CMB) anisotropy m a y result from both scalar and tensor perturbatio... more Cosmic microwave background (CMB) anisotropy m a y result from both scalar and tensor perturbations. For a suciently narrow range of angular scales, CMB perturbations can be characterized by four parameters. Results from the Cosmic Background Explorer x one combination of the parameters, reducing the parameters to three. If CMB perturbations are from ination, there is an additional relation, reducing the parameters to two. An appropriate combination of a medium-angle and a small-angle CMB observation can test the ination hypothesis because ination cannot explain a high signal in one experiment and a l o w signal in the other.
In the early Universe, the relative abundance of a massive weakly interacting particle species "f... more In the early Universe, the relative abundance of a massive weakly interacting particle species "freezes out" when the annihilation rate becomes less than the expansion rate. Although ineffective in reducing the total number of the species, occasional annihilations still occur after freeze-out. The residual annihilations of massive particles (10 MeV m&~1 GeV) after primordial nucleosynthesis can strongly alter the light-element abundances through photodissociation. For particles with typical weak-interaction cross sections and lifetimes~&~5X10 sec, we find that the mass range m&~1 GeV is ruled out, independent of how they subsequently decay.
We consider the ultra-high energy cosmic ray (UHECR) spectrum as measured by the Pierre Auger Obs... more We consider the ultra-high energy cosmic ray (UHECR) spectrum as measured by the Pierre Auger Observatory. Top-down models for the origin of UHECRs predict an increasing photon component at energies above about 10 19.7 eV. Here we present a simple prescription to compare the Auger data with a prediction assuming a pure proton component or a prediction assuming a changing primary component appropriate for a top-down model. We find that the UHECR spectrum predicted in top-down models is a good fit to the Auger data. Eventually, Auger will measure a composition-independent spectrum and will be capable of either confirming or excluding the quantity of photons predicted in top-down models.
Monojet searches are a powerful way to place model-independent constraints on effective operators... more Monojet searches are a powerful way to place model-independent constraints on effective operators coupling dark matter to the standard model. For operators generated by the exchange of a scalar mediator, however, couplings to light quarks are suppressed and the prospect of probing such interactions through the inclusive monojet channel at the LHC is limited. We propose dedicated searches, focusing on bottom and top quark final states, to constrain this class of operators. We show that a search in mono b-jets can significantly improve current limits. The mono-b signal arises partly from direct production of b-quarks in association with dark matter, but the dominant component is from top quark pair production in the kinematic regime where one top is boosted. A search for tops plus missing energy can strengthen the bounds even more; in this case signal and background have very different missing energy distributions. We find an overall improvement by several orders of magnitude in the bound on the direct detection cross section for scalar or pseudoscalar couplings.
We calculate the density fluctuations-both curvature and isocurvature-that arise due to quantum f... more We calculate the density fluctuations-both curvature and isocurvature-that arise due to quantum fluctuations in a simple model of extended inflation based upon the 3ordan-Brans-Dicke theory. Curvature fluctuations arise due to quantum fluctuations in the Brans-Dicke field, in general have a nonscale-invariant spectrum, and can have an amplitude that is cosmologically acceptable and interesting without having to tune any coupling constant to a very small value. The density perturbations the' arise due to the inflaton field are subdominaat. If there are other massless fidds in the theory, e.g., an axion or au ilion, then isocurvature fluctuations arise in these fields too. Production of gravitational waves and the massless particles associated with excitations of the Brans-Dicke field are also discussed. Several attempts at more realistic models of extended inflation are also analyzed. The importance of the Einstein conformal frame in calculating curvature fluctuations is emphasized. When viewed in this fra_ne, extended inflation closely resembles slow-rollover inflation with an exponential potential and the usual formula for the amplitude of curvature perturbations applies.
The hypothetical SUð3Þ flavor-singlet dibaryon state S with strangeness −2 has been discussed as ... more The hypothetical SUð3Þ flavor-singlet dibaryon state S with strangeness −2 has been discussed as a dark-matter candidate capable of explaining the curious 5-to-1 ratio of the mass density of dark matter to that of baryons. We study the early-universe production of dibaryons and find that irrespective of the hadron abundances produced by the QCD quark/hadron transition, rapid particle reactions thermalized the S abundance, and it tracked equilibrium until it "froze out" at a tiny value. For the plausible range of dibaryon masses (1860-1890 MeV) and generous assumptions about its interaction cross sections, S's account for at most 10 −11 of the baryon number and, thus, cannot be the dark matter. Although it is not the dark matter, if the S exists, it might be an interesting relic.
If the Universe consists of domains of matter and antimatter, annihilations at domain interfaces ... more If the Universe consists of domains of matter and antimatter, annihilations at domain interfaces leave a distinctive imprint on the Cosmic Background Radiation (CBR) sky. The signature is anisotropies in the form of long, thin ribbons of width θ W ∼ 0.1 • , separated by angle θ L ≃ 1 • (L/100h −1 Mpc) where L is the characteristic domain size, and y-distortion parameter y ≈ 10 −6. Such a pattern could potentially be detected by the high-resolution CBR anisotropy experiments planned for the next decade, and such experiments may finally settle the question of whether or not our Hubble volume is baryon symmetric.
Mikheyev and Smirnov have shown that the interactions of neutrinos with matter can result in the ... more Mikheyev and Smirnov have shown that the interactions of neutrinos with matter can result in the conversion of electron neutrinos produced in the center of the sun to muon neutrinos. Bethe has exploited this and has pointed out that the solar-neutrino puzzle can be resolved if the mass difference squared of the two neutrinos is rni-rn: Y 6 x 10e5 eV*, and the mixing angle satisfies sin Bv > 0.0065. We discuss a qualitatively different solution to the solar-neutrino puzzle which requires 1.0 x 10-s < (m:-m:)(sin'28v/cos 20") < 6.1 x 10-s eV*. Our solutions result in a much smaller flux of neutrinos from the p-p process than predicted by standard solar models, while Bethe's solution results in a flux of neutrinos from the p-p process that is about the same as standard solar models.
We extract parameters relevant for distinguishing among single-field inflation models from the Wi... more We extract parameters relevant for distinguishing among single-field inflation models from the Wilkinson Microwave Anisotropy Probe (WMAP) three-year data set, and also from WMAP in combination with the Sloan Digital Sky Survey (SDSS) galaxy power spectrum. Our analysis leads to the following conclusions: (1) the Harrison-Zel'dovich model is consistent with both data sets at a 95% confidence level; (2) there is no strong evidence for running of the spectral index of scalar perturbations; (3) potentials of the form V / p are consistent with the data for p 2, and are marginally consistent with the WMAP data considered alone for p 4, but ruled out by WMAP combined with SDSS. We perform a ''Monte Carlo reconstruction'' of the inflationary potential, and find that: (1) there is no evidence to support an observational lower bound on the amplitude of gravitational waves produced during inflation; (2) models such as simple hybrid potentials which evolve toward an inflationary late-time attractor in the space of flow parameters are strongly disfavored by the data, (3) models selected with even a weak slow-roll prior strongly cluster in the region favoring a red power spectrum and no running of the spectral index, consistent with simple single-field inflation models.
Quantum fluctuations during inflation may be responsible for temperature anisotropies in the cosm... more Quantum fluctuations during inflation may be responsible for temperature anisotropies in the cosmic microwave background (CMB). Observations of CMB anisotropies can be used to falsify many currently popular models. In this paper we discuss the prospectus for observations of CMB anisotropies at the accuracy of planned satellite missions to reject currently popular inflation models and to provide some direction for model building.
We correct several minor errors in a recent paper, and provide simple analytic expressions for th... more We correct several minor errors in a recent paper, and provide simple analytic expressions for the mean and variance of the actual energies of the positrons detected by the Irvine-Michigan-Brookhaven and Kamiokande II groups.
... PHYSICAL REVIEW LETTERS Astrophysical Production of Fractional Charge in Broken Quantum Chrom... more ... PHYSICAL REVIEW LETTERS Astrophysical Production of Fractional Charge in Broken Quantum Chromodynamics Edward W. Kolb,(a) G. Steigman,(b) and Michael S. Turner(c) Institute for Theoretical Physics, University of California, Santa ... CALT-68-781 (to be published). 5G. ...
If dark matter is a new species of particle produced in the early universe as a cold thermal reli... more If dark matter is a new species of particle produced in the early universe as a cold thermal relic (a weakly-interacting massive particle-WIMP), its present abundance, its scattering with matter in direct-detection experiments, its present-day annihilation signature in indirect-detection experiments, and its production and detection at colliders, depend crucially on the WIMP coupling to standard-model (SM) particles. It is usually assumed that the WIMP couples to the SM sector through its interactions with quarks and leptons. In this paper we explore the possibility that the WIMP coupling to the SM sector is via electroweak gauge and Higgs bosons. In the absence of an ultraviolet-complete particle-physics model, we employ effective field theory to describe the WIMP-SM coupling. We consider both scalars and Dirac fermions as possible dark-matter candidates. Starting with an exhaustive list of operators up to dimension 8, we present detailed calculation of dark-matter annihilations to all possible final states, including γγ, γZ, γh, ZZ, Zh, W + W − , hh, and ff , and demonstrate the correlations among them. We compute the mass scale of the effective field theory necessary to obtain the correct dark-matter mass density, and well as the resulting photon line signals.
The familiar nucleosynthesis constraint on the number of neutrino species, W, » 3.4, applies to m... more The familiar nucleosynthesis constraint on the number of neutrino species, W, » 3.4, applies to massless neutrino species. An MeV-mass neutrino can have even greater impact, and we show that primordial nucleosynthesis excludes a r-neutrino mass from 0.3 to 25 MeV (Dirac) and 0.5 to 25 MeV (Majorana) provided that its lifetime r" 1 sec, and from 0.3 to 30 MeV (Dirac) and 0.5 to 32 MeV (Majorana) for r,~1 0' sec. A modest improvement in the laboratory mass limitfrom 35 to 25 MeVwould imply that the r-neutrino mass must be less than 0.5 MeV (provided r "~1 sec).
It has recently been pointed out that shortly after the electroweak phase transition (t≃10−11 sec... more It has recently been pointed out that shortly after the electroweak phase transition (t≃10−11 sec , T≃100–200 GeV ) there was a period of very effective baryon (and lepton) number violation driven by non-perturbative effects arising from the electroweak anomaly. Here we argue that as a result of these electroweak interactions the total asymmetry in leptons must be equal and opposite to the baryon asymmetry: L≡∑iLi=Le+Lμ+Lr=−B. Since the individual lepton numbers can be positive or negative, this does not preclude any large individual contribution, i.e., |Li|&amp;amp;amp;amp;gt;B. This fact has important consequences for primordial nucleosynthesis if |Li|≳1.
We search for nearby, isolated, accreting, "stellar-mass" (3 to 100M) black holes. Models suggest... more We search for nearby, isolated, accreting, "stellar-mass" (3 to 100M) black holes. Models suggest a synchrotron spectrum in visible wavelengths and some emission in X-ray wavelengths. Of 3.7 million objects in the Sloan Digital Sky Survey Early Data Release, about 150,000 objects have colors and properties consistent with such a spectrum, and 87 of these objects are X-ray sources from the ROSAT All Sky Survey. Thirty-two of these have been confirmed not to be black-holes using optical spectra. We give the positions and colors of these 55 black-hole candidates, and quantitatively rank them on their likelihood to be black holes. We discuss uncertainties the expected number of sources, and the contribution of black holes to local dark matter.
Cosmic microwave background (CMB) anisotropy m a y result from both scalar and tensor perturbatio... more Cosmic microwave background (CMB) anisotropy m a y result from both scalar and tensor perturbations. For a suciently narrow range of angular scales, CMB perturbations can be characterized by four parameters. Results from the Cosmic Background Explorer x one combination of the parameters, reducing the parameters to three. If CMB perturbations are from ination, there is an additional relation, reducing the parameters to two. An appropriate combination of a medium-angle and a small-angle CMB observation can test the ination hypothesis because ination cannot explain a high signal in one experiment and a l o w signal in the other.
In the early Universe, the relative abundance of a massive weakly interacting particle species "f... more In the early Universe, the relative abundance of a massive weakly interacting particle species "freezes out" when the annihilation rate becomes less than the expansion rate. Although ineffective in reducing the total number of the species, occasional annihilations still occur after freeze-out. The residual annihilations of massive particles (10 MeV m&~1 GeV) after primordial nucleosynthesis can strongly alter the light-element abundances through photodissociation. For particles with typical weak-interaction cross sections and lifetimes~&~5X10 sec, we find that the mass range m&~1 GeV is ruled out, independent of how they subsequently decay.
We consider the ultra-high energy cosmic ray (UHECR) spectrum as measured by the Pierre Auger Obs... more We consider the ultra-high energy cosmic ray (UHECR) spectrum as measured by the Pierre Auger Observatory. Top-down models for the origin of UHECRs predict an increasing photon component at energies above about 10 19.7 eV. Here we present a simple prescription to compare the Auger data with a prediction assuming a pure proton component or a prediction assuming a changing primary component appropriate for a top-down model. We find that the UHECR spectrum predicted in top-down models is a good fit to the Auger data. Eventually, Auger will measure a composition-independent spectrum and will be capable of either confirming or excluding the quantity of photons predicted in top-down models.
Monojet searches are a powerful way to place model-independent constraints on effective operators... more Monojet searches are a powerful way to place model-independent constraints on effective operators coupling dark matter to the standard model. For operators generated by the exchange of a scalar mediator, however, couplings to light quarks are suppressed and the prospect of probing such interactions through the inclusive monojet channel at the LHC is limited. We propose dedicated searches, focusing on bottom and top quark final states, to constrain this class of operators. We show that a search in mono b-jets can significantly improve current limits. The mono-b signal arises partly from direct production of b-quarks in association with dark matter, but the dominant component is from top quark pair production in the kinematic regime where one top is boosted. A search for tops plus missing energy can strengthen the bounds even more; in this case signal and background have very different missing energy distributions. We find an overall improvement by several orders of magnitude in the bound on the direct detection cross section for scalar or pseudoscalar couplings.
We calculate the density fluctuations-both curvature and isocurvature-that arise due to quantum f... more We calculate the density fluctuations-both curvature and isocurvature-that arise due to quantum fluctuations in a simple model of extended inflation based upon the 3ordan-Brans-Dicke theory. Curvature fluctuations arise due to quantum fluctuations in the Brans-Dicke field, in general have a nonscale-invariant spectrum, and can have an amplitude that is cosmologically acceptable and interesting without having to tune any coupling constant to a very small value. The density perturbations the' arise due to the inflaton field are subdominaat. If there are other massless fidds in the theory, e.g., an axion or au ilion, then isocurvature fluctuations arise in these fields too. Production of gravitational waves and the massless particles associated with excitations of the Brans-Dicke field are also discussed. Several attempts at more realistic models of extended inflation are also analyzed. The importance of the Einstein conformal frame in calculating curvature fluctuations is emphasized. When viewed in this fra_ne, extended inflation closely resembles slow-rollover inflation with an exponential potential and the usual formula for the amplitude of curvature perturbations applies.
The hypothetical SUð3Þ flavor-singlet dibaryon state S with strangeness −2 has been discussed as ... more The hypothetical SUð3Þ flavor-singlet dibaryon state S with strangeness −2 has been discussed as a dark-matter candidate capable of explaining the curious 5-to-1 ratio of the mass density of dark matter to that of baryons. We study the early-universe production of dibaryons and find that irrespective of the hadron abundances produced by the QCD quark/hadron transition, rapid particle reactions thermalized the S abundance, and it tracked equilibrium until it "froze out" at a tiny value. For the plausible range of dibaryon masses (1860-1890 MeV) and generous assumptions about its interaction cross sections, S's account for at most 10 −11 of the baryon number and, thus, cannot be the dark matter. Although it is not the dark matter, if the S exists, it might be an interesting relic.
If the Universe consists of domains of matter and antimatter, annihilations at domain interfaces ... more If the Universe consists of domains of matter and antimatter, annihilations at domain interfaces leave a distinctive imprint on the Cosmic Background Radiation (CBR) sky. The signature is anisotropies in the form of long, thin ribbons of width θ W ∼ 0.1 • , separated by angle θ L ≃ 1 • (L/100h −1 Mpc) where L is the characteristic domain size, and y-distortion parameter y ≈ 10 −6. Such a pattern could potentially be detected by the high-resolution CBR anisotropy experiments planned for the next decade, and such experiments may finally settle the question of whether or not our Hubble volume is baryon symmetric.
Mikheyev and Smirnov have shown that the interactions of neutrinos with matter can result in the ... more Mikheyev and Smirnov have shown that the interactions of neutrinos with matter can result in the conversion of electron neutrinos produced in the center of the sun to muon neutrinos. Bethe has exploited this and has pointed out that the solar-neutrino puzzle can be resolved if the mass difference squared of the two neutrinos is rni-rn: Y 6 x 10e5 eV*, and the mixing angle satisfies sin Bv > 0.0065. We discuss a qualitatively different solution to the solar-neutrino puzzle which requires 1.0 x 10-s < (m:-m:)(sin'28v/cos 20") < 6.1 x 10-s eV*. Our solutions result in a much smaller flux of neutrinos from the p-p process than predicted by standard solar models, while Bethe's solution results in a flux of neutrinos from the p-p process that is about the same as standard solar models.
We extract parameters relevant for distinguishing among single-field inflation models from the Wi... more We extract parameters relevant for distinguishing among single-field inflation models from the Wilkinson Microwave Anisotropy Probe (WMAP) three-year data set, and also from WMAP in combination with the Sloan Digital Sky Survey (SDSS) galaxy power spectrum. Our analysis leads to the following conclusions: (1) the Harrison-Zel'dovich model is consistent with both data sets at a 95% confidence level; (2) there is no strong evidence for running of the spectral index of scalar perturbations; (3) potentials of the form V / p are consistent with the data for p 2, and are marginally consistent with the WMAP data considered alone for p 4, but ruled out by WMAP combined with SDSS. We perform a ''Monte Carlo reconstruction'' of the inflationary potential, and find that: (1) there is no evidence to support an observational lower bound on the amplitude of gravitational waves produced during inflation; (2) models such as simple hybrid potentials which evolve toward an inflationary late-time attractor in the space of flow parameters are strongly disfavored by the data, (3) models selected with even a weak slow-roll prior strongly cluster in the region favoring a red power spectrum and no running of the spectral index, consistent with simple single-field inflation models.
Quantum fluctuations during inflation may be responsible for temperature anisotropies in the cosm... more Quantum fluctuations during inflation may be responsible for temperature anisotropies in the cosmic microwave background (CMB). Observations of CMB anisotropies can be used to falsify many currently popular models. In this paper we discuss the prospectus for observations of CMB anisotropies at the accuracy of planned satellite missions to reject currently popular inflation models and to provide some direction for model building.
We correct several minor errors in a recent paper, and provide simple analytic expressions for th... more We correct several minor errors in a recent paper, and provide simple analytic expressions for the mean and variance of the actual energies of the positrons detected by the Irvine-Michigan-Brookhaven and Kamiokande II groups.
... PHYSICAL REVIEW LETTERS Astrophysical Production of Fractional Charge in Broken Quantum Chrom... more ... PHYSICAL REVIEW LETTERS Astrophysical Production of Fractional Charge in Broken Quantum Chromodynamics Edward W. Kolb,(a) G. Steigman,(b) and Michael S. Turner(c) Institute for Theoretical Physics, University of California, Santa ... CALT-68-781 (to be published). 5G. ...
If dark matter is a new species of particle produced in the early universe as a cold thermal reli... more If dark matter is a new species of particle produced in the early universe as a cold thermal relic (a weakly-interacting massive particle-WIMP), its present abundance, its scattering with matter in direct-detection experiments, its present-day annihilation signature in indirect-detection experiments, and its production and detection at colliders, depend crucially on the WIMP coupling to standard-model (SM) particles. It is usually assumed that the WIMP couples to the SM sector through its interactions with quarks and leptons. In this paper we explore the possibility that the WIMP coupling to the SM sector is via electroweak gauge and Higgs bosons. In the absence of an ultraviolet-complete particle-physics model, we employ effective field theory to describe the WIMP-SM coupling. We consider both scalars and Dirac fermions as possible dark-matter candidates. Starting with an exhaustive list of operators up to dimension 8, we present detailed calculation of dark-matter annihilations to all possible final states, including γγ, γZ, γh, ZZ, Zh, W + W − , hh, and ff , and demonstrate the correlations among them. We compute the mass scale of the effective field theory necessary to obtain the correct dark-matter mass density, and well as the resulting photon line signals.
The familiar nucleosynthesis constraint on the number of neutrino species, W, » 3.4, applies to m... more The familiar nucleosynthesis constraint on the number of neutrino species, W, » 3.4, applies to massless neutrino species. An MeV-mass neutrino can have even greater impact, and we show that primordial nucleosynthesis excludes a r-neutrino mass from 0.3 to 25 MeV (Dirac) and 0.5 to 25 MeV (Majorana) provided that its lifetime r" 1 sec, and from 0.3 to 30 MeV (Dirac) and 0.5 to 32 MeV (Majorana) for r,~1 0' sec. A modest improvement in the laboratory mass limitfrom 35 to 25 MeVwould imply that the r-neutrino mass must be less than 0.5 MeV (provided r "~1 sec).
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Papers by Edward Kolb