S. -H. Henry Tye

The Hong Kong University of Science and Technology, Chiu-lung, Kowloon City, Hong Kong

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Publications (155)533.17 Total impact

  • Source
    S. -H. Henry Tye, Sam S. C. Wong
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    ABSTRACT: Recent BICEP2 detection of low-multipole B-mode polarization anisotropy in the cosmic microwave background radiation supports the inflationary universe scenario and suggests a large inflation field range. The latter can be achieved with axion fields in the framework of string theory. We present such a helical model which reduces to the (quadratic) chaotic inflation model in the limit. Its slightly smaller tensor/scalar ratio $r$ provides a signature of the periodic nature of axion potentials. As axions are intimately related to strings/vortices and strings are ubiquitous in string theory, we explore the possibility that cosmic strings may be contributing to the B-mode polarization anisotropy observed.
    04/2014;
  • S. -H. Henry Tye, Sam S. C. Wong
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    ABSTRACT: Recent BICEP2 detection of low-multipole B-mode polarization anisotropy in the cosmic microwave background radiation supports the inflationary universe scenario and suggests a large inflaton field range. The latter feature can be achieved with axion fields in the framework of string theory. We present such a helical model which naturally becomes a model with a single cosine potential, and which in turn reduces to the (quadratic) chaotic inflation model in the super-Planckian limit. The slightly smaller tensor/scalar ratio $r$ of models of this type provides a signature of the periodic nature of an axion potential. We present a simple way to quantify this distinctive feature. As axions are intimately related to strings/vortices and strings are ubiquitous in string theory, we explore the possibility that cosmic strings may be contributing to the B-mode polarization anisotropy observed.
    03/2014;
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    Yoske Sumitomo, S. -H. Henry Tye, Sam S. C. Wong
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    ABSTRACT: We study a racetrack model in the presence of the leading alpha'-correction in flux compactification in Type IIB string theory, for the purpose of getting conceivable de-Sitter vacua in the large compactified volume approximation. Unlike the K\"ahler Uplift model studied previously, the alpha'-correction is more controllable for the meta-stable de-Sitter vacua in the racetrack case since the constraint on the compactified volume size is very much relaxed. We find that the vacuum energy density \Lambda for de-Sitter vacua approaches zero exponentially as the volume grows. We also analyze properties of the probability distribution of \Lambda in this class of models. As in other cases studied earlier, the probability distribution again peaks sharply at \Lambda=0. We also study the Racetrack K\"ahler Uplift model in the Swiss-Cheese type model.
    Journal of High Energy Physics 05/2013; 2013(7). · 5.62 Impact Factor
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    Yoske Sumitomo, S. -H. Henry Tye
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    ABSTRACT: We study the probability distribution P(\Lambda) of the cosmological constant \Lambda in a specific set of KKLT type models of supersymmetric IIB vacua. We show that, as we sweep through the quantized flux values in this flux compactification, P(\Lambda) behaves divergent at \Lambda =0^- and the median magnitude of \Lambda drops exponentially as the number of complex structure moduli h^{2,1} increases. Also, owing to the hierarchical and approximate no-scale structure, the probability of having a positive Hessian (mass squared matrix) approaches unity as h^{2,1} increases.
    Physics Letters B 11/2012; 723(4). · 4.57 Impact Factor
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    Yoske Sumitomo, S. -H. Henry Tye
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    ABSTRACT: Based on the properties of probability distributions of functions of random variables, we proposed earlier a simple stringy mechanism that prefers the meta-stable vacua with a small cosmological constant \Lambda. As an illustration of this approach, we study in this paper particularly simple but non-trivial models of the K\"ahler uplift in the large volume flux compactification scenario in Type IIB string theory, where all parameters introduced in the model are treated either as fixed constants motivated by physics, or as random variables with some given uniform probability distributions. We determine the value w_0 of the superpotential W_0 at the supersymmetric minima, and find that the resulting probability distribution P(w_0) peaks at w_0=0; furthermore, this peaking behavior strengthens as the number of complex structure moduli increases. The resulting probability distribution P(\Lambda) for meta-stable vacua also peaks as \Lambda -> 0, for both positive and negative \Lambda. This peaking/divergent behavior of P(\Lambda) strengthens as the number of moduli increases. In some scenarios for \Lambda > 0, the likely value of \Lambda decreases exponentially as the number of moduli increases. The light cosmological moduli issue accompanying a very small \Lambda is also mentioned.
    Journal of Cosmology and Astroparticle Physics 09/2012; 2013(02). · 6.04 Impact Factor
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    Yoske Sumitomo, S. -H. Henry Tye
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    ABSTRACT: Based on the probability distributions of products of random variables, we propose a simple stringy mechanism that prefers the meta-stable vacua with a small cosmological constant. We state some relevant properties of the probability distributions of functions of random variables. We then illustrate the mechanism within the flux compactification models in Type IIB string theory. As a result of the stringy dynamics, we argue that the generic probability distribution for the meta-stable vacua typically peaks with a divergent behavior at the zero value of the cosmological constant. However, its suppression in the single modulus model studied here is modest.
    Journal of Cosmology and Astroparticle Physics 04/2012; 2012(08). · 6.04 Impact Factor
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    S.-h.henry Tye, Danielwohns, Yangzhang
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    ABSTRACT: We study Coleman–de Luccia tunneling in some detail. We show that, for a single scalar field potential with a true and a false vacuum, there are four types of tunneling, depending on the properties of the potential. A general tunneling process involves a combination of thermal (Gibbons–Hawking temperature) fluctuation part way up the barrier followed by quantum tunneling. The thin-wall approximation is a special limit of the case (of only quantum tunneling) where inside the nucleation bubble is the true vacuum while the outside reaches the false vacuum. Hawking–Moss tunneling is the (only thermal fluctuation) limit of the case where the inside of the bubble does not reach the true vacuum at the moment of its creation, and the outside is cut off by the de Sitter horizon before it reaches the false vacuum. A typical tunneling process is a combination of thermal and quantum tunnelings. We estimate the tunneling rate for this case and find that the corrections to the Hawking–Moss formula can be large. In all cases, we see that the Euclidean action of the bounce decreases rapidly as the vacuum energy density increases, signaling that the tunneling is not exponentially suppressed. This phenomenon may be interpreted as a finite temperature effect due to the Gibbons–Hawking temperature of the de Sitter space. As an application, we discuss the implication of this tunneling property to the cosmic landscape.
    International Journal of Modern Physics A 01/2012; 25(05). · 1.13 Impact Factor
  • Hikarukawai, David C.lewellen, S.-h.henry Tye
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    ABSTRACT: The spin structure construction of four-dimensional fermionic string models of the heterotic type is extended by considering a generalized form of the world-sheet super-current. The rules for model building are given and illustrated with two sets of examples: the original spin structure construction and the Z3 asymmetric orbifold.
    International Journal of Modern Physics A 01/2012; 03(01). · 1.13 Impact Factor
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    ABSTRACT: We review the construction and classification of three-family grand unified models within the framework of asymmetric orbifolds in perturbative heterotic superstring. We give a detailed survey of all such models which is organized to aid analysis of their phenomenological properties. We compute tree level superpotentials for these models. These superpotentials are used to analyze the issues of proton stability (doublet–triplet splitting and R-parity-violating terms) and Yukawa mass matrices. To have agreement with phenomenological data all these models seem to require a certain degree of fine-tuning. We also analyze the possible patterns of supersymmetry breaking in these models. We find that the supersymmetry breaking scale comes out either too high to explain the electroweak hierarchy problem, or below the electroweak scale unless some degree of fine-tuning is involved. Thus, none of the models at hand seem to be phenomenologically flawless.
    International Journal of Modern Physics A 01/2012; 13(15). · 1.13 Impact Factor
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    Xingang Chen, Gary Shiu, Yoske Sumitomo, S. -H. Henry Tye
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    ABSTRACT: The search for classically stable Type IIA de-Sitter vacua typically starts with an ansatz that gives Anti-de-Sitter supersymmetric vacua and then raises the cosmological constant by modifying the compactification. As one raises the cosmological constant, the couplings typically destabilize the classically stable vacuum, so the probability that this approach will lead to a classically stable de-Sitter vacuum is Gaussianly suppressed. This suggests that classically stable de-Sitter vacua in string theory (at least in the Type IIA region), especially those with relatively high cosmological constants, are very rare. The probability that a typical de-Sitter extremum is classically stable (i.e., tachyon-free) is argued to be Gaussianly suppressed as a function of the number of moduli.
    Journal of High Energy Physics 12/2011; 2012(4). · 5.62 Impact Factor
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    I-Sheng Yang, S. -H. Henry Tye, Benjamin Shlaer
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    ABSTRACT: We argue that classical transitions can be the key to explaining the long standing puzzle of the fast A-B phase transition observed in superfluid Helium 3 while standard theory expects it to be unobservably slow. Collisions between domain walls are shown to be capable of reaching phases inaccessible through homogenous nucleation on the measured timescales. We demonstrate qualitative agreements with prior observations and provide a definite, distinctive prediction that could be verified through future experiments or, perhaps, a specific analysis of existing data.
    10/2011;
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    S.-H. Henry Tye, Daniel Wohns
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    ABSTRACT: The A phase and the B phase of superfluid He-3 are well studied, both theoretically and experimentally. The decay time scale of the A phase to the B phase of a typical supercooled superfluid 3He-A sample is calculated to be 1020,000 years or longer, yet the actual first-order phase transition of supercooled A phase happens very rapidly (in seconds to minutes) in the laboratory. We propose that this very fast phase transition puzzle can be explained by the resonant tunneling effect in field theory, which generically happens since the degeneracies of both the A and the B phases are lifted by many small interaction effects. This explanation predicts the existence of peaks in the A→B transition rate for certain values of the temperature, pressure, and magnetic field. Away from these peaks, the transition simply will not happen.
    Physical review. B, Condensed matter 01/2011; 84(18). · 3.77 Impact Factor
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    S.-H. Henry Tye, Jiajun Xu
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    ABSTRACT: We comment on Weinberg’s interesting analysis of asymptotically safe inflation [ S. Weinberg Phys. Rev. D 81 083535 (2010)]. We find that even if the gravity theory exhibits an ultraviolet fixed point, the energy scale during inflation is way too low to drive the theory close to the fixed point value. We choose the specific renormalization group flow away from the fixed point towards the infrared region that reproduces the Newton’s constant and today’s cosmological constant. We follow this renormalization group flow path to scales below the Planck scale to study the stability of the inflationary scenario. Again, we find that some fine-tuning is necessary to get enough e folds of inflation in the asymptotically safe inflationary scenario.
    Physical review D: Particles and fields 12/2010; 82(12).
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    Daniel Wohns, Jiajun Xu, S. -H. Henry Tye
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    ABSTRACT: We propose a new way to implement an inflationary prior to a cosmological dataset that incorporates the inflationary observables at arbitrary order. This approach employs an exponential form for the Hubble parameter $H(\phi)$ without taking the slow-roll approximation. At lowest non-trivial order, this $H(\phi)$ has the unique property that it is the solution to the brachistochrone problem for inflation.
    Journal of Cosmology and Astroparticle Physics 12/2010; 4(04). · 6.04 Impact Factor
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    S.-H. Henry Tye, Yang Zhang
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    ABSTRACT: Recently, Bjerrum-Bohr, Damgaard, Feng, and Sondergaard derived a set of new interesting quadratic identities of the Yang-Mills (YM) tree scattering amplitudes, besides Bern-Carrasco-Johansson (BCJ) identities. Here we comment that these quadratic identities of YM amplitudes actually follow directly from the KLT (Kawai-Lewellen-Tye) relation for graviton-dilaton-axion scattering amplitudes (in four-dimensional spacetime). This clarifies their physical origin and also provides a simpler version of the new identities. We also comment that the recently discovered BCJ identities of YM helicity amplitudes, at least for the maximal helicity-violating case, can be verified by using (repeatedly) the Schouten identity. We also point out additional quadratic identities that can be written down from the KLT relations.
    Physical review D: Particles and fields 10/2010; 82(8).
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    S. -H. Henry Tye, Yang Zhang
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    ABSTRACT: Recently, Bern, Carrasco and Johansson conjectured dual identities inside the gluon tree scattering amplitudes. In this paper, we use the properties of the heterotic string and open string tree scattering amplitudes to refine and derive these dual identities. These identities can be carried over to loop amplitudes using the unitarity method. Furthermore, given the $M$-gluon (as well as gluon-gluino) tree amplitudes, $M$-graviton (as well as graviton-gravitino) tree scattering amplitudes can be written down immediately, avoiding the derivation of Feynman rules and the evaluation of Feynman diagrams for graviton scattering amplitudes.
    Journal of High Energy Physics 03/2010; · 5.62 Impact Factor
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    S.-H. Henry Tye, Jiajun Xu
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    ABSTRACT: If the cosmological inflationary scenario took place in the cosmic landscape in string theory, the inflaton, the scalar mode responsible for inflation, would have meandered in a complicated multi-dimensional potential. We show that this meandering property naturally leads to many e-folds of inflation, a necessary condition for a successful inflationary scenario. This behavior also leads to fluctuations in the primordial power spectrum of the cosmic microwave background radiation, which may be detected in a near future cosmic variance limited experiment like PLANCK.
    Physics Letters B 01/2010; · 4.57 Impact Factor
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    S. -H. Henry Tye, Daniel Wohns
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    ABSTRACT: The resonant tunneling phenomenon is well understood in quantum mechanics. We argue why a similar phenomenon must be present in quantum field theory. We then use the functional Schr\"odinger method to show how resonant tunneling through multiple barriers takes place in quantum field theory with a single scalar field. We also show how this phenomenon in scalar quantum field theory can lead to an exponential enhancement of the single-barrier tunneling rate. Our analysis is carried out in the thin-wall approximation. Comment: 25 pages, 11 figures
    10/2009;
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    S. -H. Henry Tye, Jiajun Xu, Yang Zhang
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    ABSTRACT: Motivated by the possibility of inflation in the cosmic landscape, which may be approximated by a complicated potential, we study the density perturbations in multi-field inflation with a random potential. The random potential causes the inflaton to undergo a Brownian motion with a drift in the D-dimensional field space. To quantify such an effect, we employ a stochastic approach to evaluate the two-point and three-point functions of primordial perturbations. We find that in the weakly random scenario the resulting power spectrum resembles that of the single field slow-roll case, with up to 2% more red tilt. The strongly random scenario, leads to rich phenomenologies, such as primordial fluctuations in the power spectrum on all angular scales. Such features may already be hiding in the error bars of observed CMB TT (as well as TE and EE) power spectrum and can be detected or falsified with more data coming in the future. The tensor power spectrum itself is free of fluctuations and the tensor to scalar ratio is enhanced. In addition a large negative running of the power spectral index is possible. Non-Gaussianity is generically suppressed by the growth of adiabatic perturbations on super-horizon scales, but can possibly be enhanced by resonant effects or arise from the entropic perturbations during the onset of (p)reheating. The formalism developed in this paper can be applied to a wide class of multi-field inflation models including, e.g. the N-flation scenario.
    Journal of Cosmology and Astroparticle Physics 01/2009; · 6.04 Impact Factor
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    ABSTRACT: Cosmic string networks generate cosmological perturbations actively throughout the history of the universe. Thus, the string sourced anisotropy of the cosmic microwave background is not affected by Silk damping as much as the anisotropy seeded by inflation. The spectrum of perturbations generated by strings does not match the observed CMB spectrum on large angular scales (l<1000) and is bounded to contribute no more than 10% of the total power on those scales. However, when this bound is marginally saturated, the anisotropy created by cosmic strings on small angular scales l>2000 will dominate over that created by the primary inflationary perturbations. This range of angular scales in the CMB is presently being measured by a number of experiments; their results will test this prediction of cosmic string networks soon. Comment: 5 pages, 2 figures; improved fitting formula at 1000<l<3500, typos fixed
    Journal of Cosmology and Astroparticle Physics 04/2008; · 6.04 Impact Factor

Publication Stats

8k Citations
533.17 Total Impact Points

Institutions

  • 2011–2013
    • The Hong Kong University of Science and Technology
      • Institute for Advanced Study (IAS)
      Chiu-lung, Kowloon City, Hong Kong
  • 1979–2012
    • Cornell University
      • • Laboratory for Elementary Particle Physics
      • • Center for Radiophysics and Space Research (CRSR)
      Ithaca, New York, United States
  • 2008
    • Perimeter Institute for Theoretical Physics
      Waterloo, Ontario, Canada
  • 2006
    • Columbia University
      • Department of Physics
      New York City, New York, United States
  • 1996–1999
    • Harvard University
      Cambridge, Massachusetts, United States
  • 1992
    • McGill University
      • Department of Physics
      Montréal, Quebec, Canada
  • 1978–1985
    • Fermi National Accelerator Laboratory (Fermilab)
      Batavia, Illinois, United States
  • 1976–1977
    • Stanford University
      • Stanford Linear Accelerator Center
      Palo Alto, CA, United States
  • 1971–1975
    • Massachusetts Institute of Technology
      • Laboratory for Nuclear Science
      Cambridge, MA, United States