Bulletin of the American Physical Society
APS April Meeting 2021
Volume 66, Number 5
Saturday–Tuesday, April 17–20, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session L18: New Development in Theoretical Physics and CosmologyLive
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Sponsoring Units: DPF Chair: Gary Shiu, Wisconsin |
Sunday, April 18, 2021 3:45PM - 3:57PM Live |
L18.00001: Confinement and Graded Partition Functions for $\mathcal{N} =\,\,$4 SYM Aditya Dhumuntarao, Aleksey Cherman Gauge theories with confining phases at low temperatures tend to deconfine at high temperatures. In some cases, for example in supersymmetric theories, confinement can persist for all temperatures provided the partition function includes a grading by $(-1)^F$. When it is possible to define partition functions which smoothly interpolate between no grading an $(-1)^F$ grading, it is natural to ask if there are other choices of grading that have the same effect as $(-1)^F$ on confinement. We explore how this works for $\mathcal{N} =\,\,$4 SYM on $S^1\times S^3$ in the large $N$ limit at both small and large coupling. We find evidence for a continuous range of grading parameters that preserve confinement for all temperatures at large coupling, while at small coupling only a discrete set of gradings preserve confinement. [Preview Abstract] |
Sunday, April 18, 2021 3:57PM - 4:09PM Live |
L18.00002: UV Renormalization and Late-time Resummation of Correlation Functions in Minkowski. Spasen Chaykov, Nishant Agarwal, Sina Bahrami, Richard Holman I will present results on the UV renormalization and late-time behavior of correlation functions in self-interacting scalar field theories on a Minkowski background when starting the evolution at some initial time. In particular, we are interested in the unequal-time two-point correlator where we expect to see a breakdown of perturbation theory analogous to equal-time correlators on time-dependent backgrounds. I will first show that renormalization counterterms need to be considered in both the dynamics and the initial state. Taking these into account, we find a linear and log secular growth for interactions of mass dimension one and zero, respectively. I will next discuss the Weisskopf-Wigner method to calculate resummed correlators and show that it gives an exact exponentiation of the late-time perturbative result. Our results offer a potential path to understanding renormalization and late-time resummations in more complicated spacetimes with explicit time-dependence and/or a horizon. [Preview Abstract] |
Sunday, April 18, 2021 4:09PM - 4:21PM Live |
L18.00003: A new definition of local complexity in quantum field theories Curtis Asplund, Elisa Panciu We introduce a generalization of entanglement entropy that quantifies the predictive complexity of subsystems of extended quantum systems, including quantum field theories. Interest in finding good notions of quantum complexity is high, including from conformal field theory and holographic gauge-gravity duality. The quantity we introduce is calculated by applying an equivalence relation to states exterior to a subsystem that are dynamically equivalent with regard to that subsystem. The equivalence relation reduces the effective entanglement entropy and results in a measure of the local complexity. This definition is inspired by the ``statistical complexity" defined for (non-quantum) stochastic processes. We present calculations of this measure in the Heisenberg model of a spin chain and show the effects of both scattering states and bound states. We then discuss this quantity for quantum field theories and the prospects for it to be a useful new way to analyze the complexities of states and processes in quantum field theories and other quantum systems. [Preview Abstract] |
Sunday, April 18, 2021 4:21PM - 4:33PM Live |
L18.00004: Landscapes of Quantum Field Theories via the Eisenhart Lift Sotirios Karamitsos, Kieran Finn, Apostolos Pilaftsis The gauge hierarchy problem and the cosmological constant problem are two of the most prominent examples of fine-tuning in modern physics. A possible way to evade them is by postulating the existence of a multiverse from which a viable universe may be selected under anthropic considerations. In this talk, I will present an application of the Eisenhart lift to field theories that can give rise to hierarchies by purely geometric means. The Eisenhart lift is a formalism that reproduces the dynamics of a classical system subject to a potential by means of a free system evolving in a higher-dimensional curved manifold. I will first outline the generalization of the classical lift to quantum mechanics, and then demonstrate that an ensemble of Fock spaces can be embedded in a curved \emph{field-space} manifold. These spaces are disjoint from one another, and are indexed by a conserved quantum charge which corresponds to a physical constant. Therefore, this ensemble acts as a novel kind of a landscape, providing a novel avenue for generating hierarchies and dealing with fine-tuning issues. [Preview Abstract] |
Sunday, April 18, 2021 4:33PM - 4:45PM Live |
L18.00005: Unification of the Four Forces in the Spin (11,1) Geometric Algebra Andrew Hamilton The spinors of the group Spin($N$) of rotations in $N$ spacetime dimensions are indexed by a bitcode with $[N/2]$ bits. A well-known promising grand unified group that contains the standard-model group is Spin(10). Fermions in the standard model are described by five bits $durgb$, consisting of two weak bits $d$ and $u$, and three color bits $r$, $g$, $b$. If a sixth bit $T$ is added, necessary to accommodate a time dimension, then the enlarged Spin(11,1) algebra contains the standard-model and Dirac algebras as commuting subalgebras, unifying all four forces. The largest subgroup of Spin(11,1) that commutes with the Poincar\'e group is Spin(5)$\,\times\,$Spin(6), suggesting that the latter is a partial unification on the way to complete unification in Spin(11,1). The Spin(5)$\,\times\,$Spin(6) algebra contains a subalgebra with precisely the properties of the electroweak Higgs field. The Spin(5)$\,\times\,$Spin(6) symmetry contains, and is spontaneously broken by, a U(1) symmetry related to the U$_{B-L}$(1) symmetry. Grand unification is associated with a change in the dimensionality of spacetime. [Preview Abstract] |
Sunday, April 18, 2021 4:45PM - 4:57PM Live |
L18.00006: Information content in the redshift-space galaxy power spectrum and bispectrum Nishant Agarwal, Vincent Desjacques, Donghui Jeong, Fabian Schmidt The small-scale distribution of matter is a sensitive probe of various cosmological parameters. Extracting unbiased constraints from these scales, however, requires careful consideration of nonlinear gravitational evolution, nonlinear biasing, and line-of-sight dependent selection effects. I will present a Fisher information study of the statistical impact of galaxy bias and selection effects on the estimation of key cosmological parameters from galaxy redshift surveys; in particular, the angular diameter distance, Hubble parameter, and linear growth rate at a given redshift, cold dark matter density, and tilt and running of the primordial power spectrum. I will show that including the one-loop galaxy power spectrum and tree-level bispectrum helps break various parameter degeneracies and recovers cosmological information that would otherwise be lost in modeling the observed distribution of matter on small scales. [Preview Abstract] |
Sunday, April 18, 2021 4:57PM - 5:09PM Live |
L18.00007: Reconciling dark cosmology by duality in the Friedmann scale factor Maurice Van Putten We report on a duality $D(a)+D(\kappa)=2$ satisfied by the Friedmann scale factor $a$ with curvature $\kappa=1/a$ in terms of the nondimensional operator $D(u)=\ddot{u}u/\dot{u}^2$. The Hubble parameter hereby satisfies $H(z)=H_0\sqrt{1+A(z)}/(1+z)$, where $A(z)$ is a polynomial in the normalized densities of radiation, matter and curvature at redshift $z=0$. Late-time three-flat cosmology satisfies $D(\kappa)=3\Omega_M$. With no free parameters, it alleviates $H_0$-tension between $\Lambda$CDM and the Local Distance Ladder consistent with the age of the Universe based on globular clusters. The mass of the associated dark matter particle is herein bounded by $8.8\times 10^{-24}$eV by what appears to be $C^0$-galaxy dynamics in SPARC galaxy rotation curves. (Based on van Putten, 2020, MNRAS, 491, L6.) [Preview Abstract] |
Sunday, April 18, 2021 5:09PM - 5:21PM Live |
L18.00008: Non-minimally coupled quartic inflation with radiative corrections in the Palatini formulation Nilay Bostan In this talk, we discuss how the non-minimal coupling $\xi \phi^2 R$ between the inflaton and the Ricci scalar affects the predictions of single-field inflation models in the Palatini formulation. Interaction between the inflaton and other fields lead to radiative corrections in the inflationary potential. These radiative corrections can be expressed at leading order Coleman-Weinberg (CW) one-loop corrections. The impact of these corrections to the inflationary potential have been investigated by using two different prescriptions discussed in the literature. We show the range of coupling parameters between couplings of the inflaton to bosons and fermions for which the spectral index $n_s$ and the tensor-to-scalar ratio $r$ are compatible with data taken by the Keck Array/BICEP2 and Planck collaborations. [Preview Abstract] |
Sunday, April 18, 2021 5:21PM - 5:33PM Live |
L18.00009: Revisiting the Cosmological Constant Problem within~Quantum Cosmology Vesselin Gueorguiev, Andre Maeder The Cosmological Constant (CC) problem is discussed within the multiverse context. It is assumed that each member of the ensemble of universes has a characteristic scale $a$ that can be used as integration variable. An averaged characteristic scale $\bar{a}$ of the ensemble is estimated by using only members that satisfy the Einstein Field Equations (EFEs). The $\bar{a}$ is compatible with the Planck length when considering an ensemble of solutions to the EFEs. The multiverse ensemble is split in Planck-seed universes with vacuum energy density of order one and $a$-derivable universes. For $a$-derivable universe with a characteristic scale of the order of the observed Universe $a\approx 8\times10^{60}$, one has $\Lambda=\tilde{\Lambda}/a^{2}$ is in the range $10^{-121}$--$10^{-122}$, which is close in magnitude to the observed value $10^{-123}$. We point out that the smallness of $\Lambda$ can be viewed to be natural if its value is associated with the entropy of the Universe. This approach to the CC problem reconciles the Planck-scale huge vacuum energy--density predicted by QFT considerations, as valid for Planck-seed universes, with the observed small value of the CC as relevant to an $a$-derivable universe as observed. [Universe 2020,{\bf 6},108; doi:10.3390/universe6080108]. [Preview Abstract] |
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